cigarette smokers (6, ~2, 11.2). but the magnitude of this reiation- ship is not as great as that with squamous cell cancer in man. Reduction in Tumorigenicity The importance of reducing total particulate matter in cigarette smoke is reflected in the dose-dependent results of the Auerbach- Hammond study. A major objective of experimental tobacco car- cinogenesis must be the reduction in the tumorigenicity of cigarette smoke and other tobacco products. In a recent article (320). Wynder and Hoffmann have reviewed the various methods applied to achieve this goal. Among these methods are the modification of the tobacco itself, the modification of the conditions of tobacco pyrolysis, the use of additives, and the use of fiIters. The use of filters shouId produce a reduction of particulate matter as well as of gas phase components. Brass (14) studied 974 cases of lung cancer at Roswell Park Nemorial Institute and concluded that smokers who switched to filter cigarettes showed a decreased risk of developing lung cancer. However, even after switching, heavy smokers were still found to have a mortality risk five times that of nonsmokers. More recently, Wynder, et al. (324) reported on an interview study of 350 patients with histologically confirmed lung cancer and 552 age and sex-matched controls. They found that subjects who had switched from nonfilter to filter cigarettes ten or more years prior to the study incurred a lower relative risk of lung cancer at all consumption levels than that incurred by those who continued to smoke nonfilter cigarettes. The authors suggest that this difference in relative risk may be due to the lower "tar" content in filter cigarette smoke. Prospective studies concerning the effects of filter cigarette smoking are presently being conducted. Apart from variations in "tar" exposure due to filtration, it appears that different patterns of smoking result in the inhalation of varied amounts of "tar." Graham, et al. (103) simulated dif- ferent inhalation patterns with the use of an analytic smoking ma-- chine. He found that smoking a given number of puffs over a long period of time results in greater "tar" retrieval than smoking them over a short period. Also, he observed that taking most of the puffs at the end of the cigarette results in the highest retrieval while taking most at the beginning results in the smallest retrieval. Complementing these observations is the same author's case/con- trol study (102) of 183 men with lung cancer and 161 men with diseases not related to tobacco smoking. He found that the lung cancer patients had significantly greater high "tar" yield cigar&e smoking patterns than the controls. The risk of lung cancer was found to increase with the increase in mean number of puffs per 301 cigarette, the average length of time taken to sm.k,-t :a cign~tZc (except in the highest number of puffs category), ti:ti, ;be rAki,% of more puffs at the end of the cigarette. These findings, and those of the study of Xuerbrrhh .I: :>, !, ~.i,j, add further support to the dose-response relationsti:, i~et~c?en- Cung, cancer and total cigarette smoke condensate expo~.rr~~.r:. SUXSIARY AND CONCLUSIONS 1. Epidemiological evidence derived from a numo::?-.C nrc:~+n~:- tive and retrospective studies coupled with experimm the main cause of lung cancer in men. These stud& yz'i-,<&~-a~ -;he risk of developing lung cancer increases with the mFizr,of. cigar: ettes smoked per day, the duration of smoking, an!:e:nCier iniaia- tion, and diminishes with cessation of smoking. 2. Cigarette smoking is a cause of lung cancel 5 xmm @rrt accounts for a smaller proportion of cases than in LF:Z, Y%: ZXX- tality rates for women who smoke, although sigti:it:zr;Jp h&iier than for female nonsmokers, are lower than for r?xtn ~dcssmok;l This difference may be at least partialIy attributed :`D ~.Lf%r~nt?r ia exposure; such as, the use of fewer cigarettes per rtiy ~ t&e :rse `3s filtered and low "tar" cigarettes, and lower level3 #& irr%a!a:ion. Nevertheless, even when women are compared w&F men v&o a?- parently have similar levels of exposure to cigar&z smoke, the mortality ratios appear to be lower in women. 3. The risk of developing lung cancer among p$e aridG>or ciwr smokers is higher than for nonsmokers but signifi~l~~:~~~~~;\re~~ &-ran for cigarette smokers. 4. The risk of developing lung cancer appears to5ehighur amor.g smokers who smoke high "tar" cigarettes or smokt in- ~~uh~a.rna~~ti ner as to produce higher levels of "tar" in the inhaM smoke.. 5. Ex-cigarette smokers have significantly lower &aUr -rates-for lung cancer than continuing smokers. There is evi&nc~~%u support the view that cessation of smoking by Iarge nurnbz=, s.f &`garette smokers would be followed by lower lung cancer &a~&: CYL%& 6. Increased death rates from lung cancer ham: 4ezz ;Itlssrved among urban populations when compared with pq~~~$~~ns~ from rural environments. The evidence concerning the rzitt $2 :tir poi'iu- tion in the etiology of lung cancer is presently incolc,r&si~~ FBctitrs such as occupational and smoking habit difference may- z&o. cm- tribute to the urban-rural difference observed. D&;+d. epjdcmio- logic surveys have shown that the urban factor ~xexi;s a smalI influence compared to the overriding effect of cig~.~~:e~ ~mok;hg in the development of lung cancer. 302 7. Certain occupational esposures have been found to be asso- ciated with an increased risk of dying from lung cancer. Cigarette smoking interacts with these esposures in the pathogen&s of lung cancer so as to produce very much higher lung cancer death rates in those cigarette smokers who are also exposed to such substances. 8. Experimental studies on animals utilizing skin painting, tracheal instillation or implantation, and inhalation of cigarette smoke or its component compounds, have confirmed the presence of complete carcinogens as well as tumor initiators and promoters in tobacco smoke. Lung cancer has been found in dogs exposed to the inhalation of cigarette smoke over a period of more than two years. CANCEROFTHELARYNX Cancer of the larynx is a disease which predominantly affects males in the 55 to 70 year age group. In 1967, a total of 2,468 males and 329 females died of laryngeal cancer in the United States. With the development and application of more effective therapy during the past 30 years, the death rate for cancer of the larynx appears to he dropping slightly (288, 289) ; however, the incidence con- tinues to rise. Figures from the Connecticut Cancer Registry (88) show that the age-adjusted incidence per 100,000 population of cancer of the larynx for males rose from 3.0 in 1950 to 5.6 in 1961. EPIDEMIOLOGICALSTUDIES A number of epidemiological studies have investigated the rela- tionship between smoking habits and the development of cancer of the larynx. The major prospective studies, as outlined in table 20, show that smokers of cigarettes run an approximately six-to- tenfold risk of dying from this form of cancer as compared to non- smokers. Smokers of pipes and cigars incur a three-to-sevenfoId risk. The retrospective studies listed in table A21 uniformly show fewer nonsmokers and more smokers among cases with cancer of the larynx than among matched controls. Table A22 summarizes- the relative risk ratios derived from the retrospective studies. The wide variation is due to a number of factors, including type of pop- lation and interview technique. But, in general, the magnitude of most of these ratios is of the same order as in the prospective studies. Wynder, et al. (31.2) have distinguished between cancer of the intrinsic and extrinsic larynx. Tumors arising on the vocal cords are classified as intrinsic and constitute approximately 70 percent of the lesions. The extrinsic larynx is composed of those sections of the larynx excluding the vocal cords and may also be referred to as 303 w 0 4. TABLE 20.--Laryngeal cancer vtortalit2/ ratios (Actual number of drnths shown in pnrenthc-ses)' Shf = Smukcrs. NS = Nonsmukcra. Prospective etudica Author. Y-2&*. country, Number and Data type of collcctlon FOUOW- U" Cizarcttes/dny Plpea, cleara Comments rcfrrr"cc DOPUlUllO" y&w dr1rtha Hammond 187.763 whlta Qucntlo""nlrs n'/JJ 24 Clgnrcttc smokers 11124. Cigar Dntn rcfsrring to mortality and males 60-68 and follow- `. s,v .24 3/24 rntlo i"Cl~~dCd ennccr of Hot", ycal-8 of age UP of Jcnth NS 0 Mizcd csophagua nnd mouth. 1966, In 9 statea. certificate. 4124 U.S.A. (IrnOl. Doll and Appr0ximatd.y Qutstlonnaire 10 16 All rmokcra by amount t Includea data on BX- Hill, Pipe and cigart 41,000 male and follow- SM ..16 in gramr NS .,.. 1.00 smokem of pipes and clunra. 1964, British "P of death NS 0 NS . . . . . . . . . . a.. . . SM . 6.00 Crut No NS died of lnr~n.geo- Dhysicinna. certificate. l-14 . . . . . . . . . . . . 1.00 BriWn tracheal esnccr, therefore 16-24 ( 71) . . . . . . . . . . . 1.00 l-14 pram SbI set 08 1.00 >?G . . . . . . ,. 4. . . . 7.60 rtrndsrd. Data combinc leryn~csl md tracheal carcinoma. Kahn U.S. male PucBtlonnorre 8% 64 NS (Darn), . . . . . . . . 1.00 (8) Pipe Refers to cu~`rc"t cipurcttc veterana, and follow- Shf .61 l-9 1866, . . . . . . ..a.... 3.27 (1) NS . . . . 1.00 (3) amokera only. 2.266.674 UP of deeth NS 3 U.S.A. la-20 , ., ., ,, ** *. * 8.46(10) SM . ...10.33 (6) Pwm" yean. ccrtlflcate. 21-39 (ISO). . . . . . . . . . . . 19.62(11) Pipe 4nd cigar >39 . ., .I ., .,, . .16.85 (3) NS .a. 1.00 (3) All . . . . . . . . . . . . . . fI.D5(26) SM .,. 7.28(11) Iinmmond. 440,658 mnln Interviewa 4 G7 1966, NS Male data only. 662.671 fe . . ..I. ,... . . 1.00 (3) Pipe and cigar by ACS U.S.A. SM .64 males 35-84 SM (aw46-60 . . 6.09(923 NS .a.. 1.00 (8) Pipe and clpar d8ts refer to volunteera. (118). YeQrl of age NS..3 SM (ngc65-79) . . 8.99(18) Sbl . ,, , 8.87 (4) m&lea KG-84 ye*" of aIC. I" 26 atatea. TABLE ZO.--LarUngcal cancer mortality ratios (cont.) (Actual number of drnth3 shown I" psrcnthcses)l Shl = Smokars. NS = Nunamokcrs. Author, Y-2.-T, eou"trY, rrfurcnce Number and type of DoPulation Data collection Cigarettcs/daY Plpca, cigars Commcnta Weir and DU"", 1870, U.S.A. (sob). 68,163 mnle. Qucc.rlonnaire 6-8 11 NS . . . ., ,. ., , - No ncnsmoken died of In various snd follow- SM ..ll ?I10 . .I ,.. . . . . 1.00 hryn~rbl carcinuma. occupatio"s "D of death NS . o 220 . ,. ., . . . 6.99 tlivrcfitrc 210 ami,Lc,r set in California. certificate. >a0 a . . . ., 6.84 ~1s 1.00 standard. NY inch\dca ulve snd clxar amukcra. Shl includes rx.smohcja. ' Unless otherwise apecifwd. disparities between the total number of dcatha xnd the aum of the Lndivldual smokins categories arc due to the exclusion of either occasional. miscellaneous. mixed, or ex-smokers W s the hypopharyns. These authors noted that the percentage of hea\-> smokers among the patients \vith cancer of both the extrinsic and intrinsic larynx was significantI>- greater than that among controls. However, it is of interest that the excess risk of laryngeal cancer among cigar and pipe smokers in this study could be attributed to the extrinsic laryngeal group. As in studies of oral cancer, it appears that alcohol consumption should also be taken into account in studies of laryngeal cancer. Wynder, et al. (315) reported a significantly increased risk of extrinsic cancer among those with alcohol intake above 7 ounces of whiskey per day. With less than this amount, no increased risk was evident. Schwartz, et al. (%8), noted no effect in relation to alcohol intake. Further research into the interaction of these two variables is necessary. PATHOLOGICALSTUDY Auerbach, et al. (9) studied histological changes in the larynges of 942 men, age 21 to 95, who were autopsied at a single hospital between 1961 and 1967. Cases of primary cancer of the larynx \vere excluded from the study. Smoking histories for all cases were obtained from family members of the deceased by trained inter- viewers. The randomized histological sections were graded by one observer. Tables A23 and A?? summarize the findings in the true vocal cord. Of the men who never smoked, 75 percent had no cells with atypical nuclei, only 4.5 percent had sections with areas con- taining 60 to 69 percent of cells with atypical nuclei, and none had a higher percentage. The 116 ex-smokers had laryngeal histology similar to that of the nonsmokers, as far as atypical nuclei were concerned. However, disintegrating nuclei were found in 40.5 per- cent of the ex-cigarette smokers and in only 0.4 percent of the remaining cases. Only one of the 91 cigar and/or pipe smokers had no atypical cells. Three had carcinoma in situ, and one case had a section showing early invasive primary carcinoma. The highest percentage of atypical cells was found among the cigarette smokers. The proportion of cases with a high degree of cellular change increased with increased daily smoking. None of the pack-or-more-a-day smokers was free of atypical nuclei in the laryngeal epithelium. Of those who smoked two or more packs per day, 85 percent had lesions with 60 percent or more atypical cells as compared to 3 percent of the nonsmokers. Retween 10 and 18 Percent of the' cigarette smokers had areas of carcinoma in site, and 4 of the 644 cases showed early microscopic invasion. The thickness of the basal level of the true vocal cord was also directly related to the amount smoked. 306 Dmtenwill (76) has recently reported the development of an effective and practicable method by lvhich small rodents (ham- sters, rats, mice) can be exposed to long-term passive inhalation of cigarette smoke in a manner which circumvents the fatal effects of acute toxicity which ruined earlier attempts but allow-s for a dosage of smoke great enough to inpuce the development of chronic patho- logical changes. The Syrian Golden hamster was found to be the most suitable species for such inhalation experiments for several reasons : its resistance to pulmonary infections, its resistance to the effects of nicotine as compared to that of rats or certain strains of mice, and, especially, its susceptibility to develop tracheobronchial cancers after treatment with carcinogens, in contrast to its almost total freedom from the spontaneous development of these tumors. Dontenwifl demonstrated that the concentration of deposited cigarette smoke was greatest in the hamster's larynx as compared to the other portions of the exposed respiratory tract (table 25), and that the laryngeal epithelium was the tissue which underwent the greatest smoke-induced histological changes. In studying the changes in the larynx, the author differentiated five stages of epithelial change, using as his reference the Atlas of Tumor Pathology of the Armed Forces Institute of Pathology (5). Table 36, quoted by Dontenwill, describes the five types of change. They range from benign, such as epithefial hyperplasia, to pre- malignant, exemplified by pseudoepitheliomatous leukoplakia. The results of the inhalation experiment are presented in figure 4 in which a dosage-related increase in the severity of the epithelial changes is represented in graphic form. The author also reported, and depicted with photomicrographs, the finding of an early inva- sive squamous cell carcinoma. This form of cancer is the predomi- nant type involving the human larynx. SUMMARY AND CONCLUSlOSS 1. Epidemiological, experimental, and pathological studies sup- port the conclusion that cigarette smoking is a significant factor in the causation of cancer of the larynx. The rizk of developing laryngeal cancer among cigarette smokers as well as pipe and/or cigar smokers is significantly higher than among nonsmokers. The magnitude of the risk for pipe and cigar smokers is about the same order as that for cigarette smokers, or possibly slightly lower. 2. Experimental exposure to the passive inhalation of cigarette smoke has been observed to produce premalignant and malignant changes in the larynx of hamsters. 307 TABLE X.-Deposition of "C-labeled smoke particles in particular regions of the respiratoqj tract' He.d and pslate _. 6.11 Head. palate TODEUC ___ _. ._... . 0.41 Oral cavity in total. Larynx _. . . . 0.39 Trachea __ __ __ __ OX Luns, . . . . 695 I Total . . . . . .14.12 EStitlll3ted Deposition radio- of activity particles (nCi) (70) 5.6 37.4 1.6 10.9 7.6 (traced1 51.7 `14.1 100.0 0.1-0.3 X561-187 0.6 X62.3 1000 Xl TABLE 26.-Classification of the five registered stages of epithcliaI changes at the laru?ix',' Dyskeratosia (nre. mnture e..(yplcril Acnnthasls (thicken- Hyperkwntosis Parakeratosls (in. cornification ing of strntum increased complete corniRcn- changes In the hlito3i3 spinosum multi- cornification tion 0Cnuelel in nucleus Drolifcrn. cellulnr kwert (rtroturu comeum) the stratum corneum) lion yf)j;,bnxaI 1. Pachydermia (cpithelirrl hywrDlania) . . . . , . . . t t t t t 6. Pseudoe~ith.liomatous leucoptakia . . ,. . . . . . t -t t tt+ t f Symbols: t = negative: $ = mlnimnl; f = weak; ++ = medium; i-4-f = BtronE. 1 From Atlas of Tumor Pathology of the Arm& Forces Institute al Pathology. SOURCE: Adapted from Dontenwlll, W. (76). TOTAL 146 2 4 ii a IO 12 14 16 18 20 22-s-3 SMOKE WPOSURE. months . ZONE ANIMAL Q=AN~MAL LIVING O=lARYNX CANNIBALIZED FIGURE do--Effects of chronic cigarette smoke inhalation on the hamster larpx. Review of the results of the inhalation experiments: number of smoke-ex- posed animals with and without changes in the larynx, duration of smoke exposure, and number of animals still alive. SOURCE: Dontenwill, `8. (76). ORAL CANCER The cancers included in this category are those of the lips, tongue, floor of the mouth, hard and soft palate, gingiva, alveolar mucosa, buccal mucosa, and oropharyns. It is estimated that 15,000 of these cancers will be diagnosed in the United States in 1970, accounting for about 2.5 percent of the estimated 600,000 malignant neo- plasms reported (289). A variety of histological types of malig- nant neoplasms can affect these tissues, but squamous cell car- cinoma is by far the predominant type, accounting for about 90 percent of the cancers. The incidence of and mortality from oral cancers has remained steady over the past 20 to 30 years. The Connecticut Cancer Res- istry (88). which is a fairly reliable index of incidence, noted that the incidence among males remained between 15.8 and 16.3 per 100,000 population during the years from 1950-1961. Examination of mortality rates over the past 20 to 30 years (P&Z, 289) reveals a similar constancy. The apparent lack of change in mortality from oral cancer in 310 contrast to the sharp increase that took place in lung cancer rates in those years is probably due to several of the following factors. First, pipe and cigar smohing are both significantly related to can- cer of the oral cavity, and the increase in cigarette smoking among men, noted between $$O and 1955, has been, to a large degree, accompanied by corresponding reductions in the use of pipes and cigars. Second, aside from the various changes ivhich the Interna- tional Classification of Diseases (ICD) had undergone during that period, the diseases discussed above are recorded in ICD Codes 140-148 which include some neoplasms not found to be related to the use of tobacco. The various sites of cancer themselves do not contribute equally to the overall rate and are subject to widely dif- ferent cure rates, so that their contributions to the total incidence rate is different from their contribution to the overall mortality rate from oral cancer. Although more than 20,000 cancers of the oral cavity were estimated as newly diagnosed in 1967, the totai number of individuals recorded as dying from oral cancer during that year was only 6,718 (ZQO). Oral cancer occurs predominantly in people of the middle and older age groups. More than 90 percent of all oral cancers occur in persons over age 45, with the average age at time of diagnosis approximating GO. Although the majority of oral cancers occur in men, there is recent evidence that the ratio of males affected to females affected is decreasing (9.57). The use of tobacco in various forms has been associated with the development of cancer of the oral cavity and pharynx. The studies in this area of concern are truly international, many having been carried out in Asian nations as well as in the West. The major pro.specti\~e epidemiological studies have found in- creased rates of these cancers for cigarette smokers as well as for pipe and cigar smokers (see table 27). Pipe smoking, per se, has- - long been recognized as a cause of lip cancer (~91) _ The methodol- ogy and results of the numerous retrospective studies are sum- marized in tables A28 and A28a. These studies almost uniformly show significant relationships between the various forms of tobacco use and c-nsr:rs of the oral cavity and pharynx. Studies in Asi:ln I~`* +iqns have examined the prevalence or inci- dence of premalignatit ch:inge, such as oral leukoplakia, as well as that of cancer of the oral cavity. In many of these studies, forms of tobacco use not prevalent in IVestern countries have been investi- gated, including reverse smoking (in which the lighted end of the cigarette is kept in the mouth close to the palate) and the chewing 311 Number and tyne of population Data collection FOIIOW- up yea14 N"omIber Cipnrettea Pipea. cIgara Comment8 deaths Hemmond 187.783 white Qucntionnaire 3 1% 66 and mnlcs in 9 and follow-up tSN .61 Horn, stntc. 3a-Go of dcnth NS ..3 1068, ycllra of nKe. ccrtincnt.zo. U.S.A. (14'0). Doll and Ap~`rurlmntrly Quratlunrrnlre 10 10 llill, 41,000 mslc nnd follow-UP Shl . ,I9 1964. llrltirh of drbth NS ..a Crrnt physicinns. ccrtificntc. Dritain (71). Kahn U.S. msle Questionnaire B!/r 61 NS ._.... l.OO(ll) Pipe Data do not Include pharynx. (Darn), veterans. and follow-up Shl .60 tCigs/dsy 1-9 . . . , 0.8C (1) NS ..*.*.. l.OO(ll) t Refera to current clgarctte 10G6, 2.265.614 of dcnth NS . .I1 lo-20 ..,,,......, 2.93(13) Shl ..,.... 2.12 (4) smoken only. U.S.A. r)utsol! yesrs. certinca1c, 21-39 . . . ., ,, 3. . . . 7.34(20) Cipar IIJY). >N . ,. . . . 6.73 (3) NS *...... l.OO(ll) All . . . . . . . . . . . . . . 4.@3(37) Shl .,..,,,. 4.11 (0) Hammond. 440,LGE malra Intcrvlcws by 4 I')CG. bG%.G71 Ivmnlea ACS vuluntccm V.S,A. .15-X4 yt:arn of (JIJ). rwc in X.5 Ststca. _. Wclr end 68.1G3 males Questionnaire 6-8 Dunn, In vnlious and follow-up 1070. occupstiona of death U.S.A. in California. certlflcnte. (SOF). of "pan" or "Xass," which are mixtures of tobacco with either betel nut or lime ash, and other ingredients (2L1, 255, ,056). Snuff dipping, a habit in which snuif is placed in the gum and retained there for prolonged periods, has also been associated with the development of oral cancer (193, 210), as has the chewing of tobacco (124,193,241,998). -The risk of developing a second primary mouth or throat cancer, after the recognition of the first primary cancer, has been found to be greater in continuing smokers than in those who quit smok- ing. All of the patients studied by Moore (190) were asymptomatic for at least three years following the treatment of the first cancer. Of the 117 patients with adequate smoking histories, only 4 of 43 (9 percent) who quit smoking developed a new primary cancer. On the other hand, 27 of 74 (36 percent) who continued to smoke developed a second primary cancer. However, a study by Castigliano (53) of patients treated for oral cancer did not show a greater risk of a second primary among continuing smokers. In this study, 5 of 26 (19 percent) of those patients who did not quit smoking developed a second primary cancer as compared to 9 of 51 (IS percent) of those who did quit. The rate of quitting smoking in the two studies is markedly dif- ferent (36 percent in the Moore study and 62 percent in the Casti- gliano study) _ From the data presented in the two papers, it is not possible to evaluate the other significant ways in which the pop- ulations may have differed. Keller (140) studied 408 males with histologically confirmed squamous cell cancer of the mouth or pharynx. This author dealt with the question of recurrent tumors in a somewhat different manner. The patients were observed for the development of a sec- ond or third primary cancer at an anatomically discrete site of the mouth and pharynx within a median period of three years after the first cancer. He found that a second or third cancer (termed a coexisting cancer) developed in 28 of the 408 cases. Among these 28 cases with 33 coexisting neoplasms, 21.7 percent were heavy: -- smokers, but among their matched controls, there were no heavy smokers. Coexisting cancers were most commonly found on the soft Palate, an anatomical site that is in direct contact with the main- stream of tobacco smoke. More recently, Wynder, et al. (315) studied 63 male and 23 female patients with multiple primary cancers of the mouth and pharynx. They observed that heavy smoking prior to the develop- ment of the oral cancer was associated with a greater likelihood of developing a.second primary. Also, continued smoking after the first primary was found to have a significant association with the occurrence of a second primary. 313 IJ'ith or without smoking, use of alcohol appears to contribute to the development of oral cancer (1_7:, 120, 15'9, 297. 32). In a study of male ve6%ans, Keller (ILO) found that heavy smoking and heavy drinking were associated with cancer of the mouth and phan-nx. No studies are presently available which determine the relative contributions and possible interactions of heavy smoking, heavy drinking, and concurrent nutritional deficiencies in the etiol- ogy of these cancers. EXPERIJIENTAL STUDIES In 196-1, the Advisory Committee to the Surgeon General on Smoking and Health (291) reported that cigarette smoke and ciga- rette smoke condensates had failed to produce cancer when applied to the oral cavity of mice and rabbits or to the palate of hamsters and that the oral mucosa appears to be resistant in general to can- cer induction even when highly active carcinogens such as benzo- [alpyrene are applied. Some of the difficulties in experimental de- sign were attributed to the fact that mechanjcal factors, such as secretion of saliva, interfere with the retention of applied carcino- genic agents on the tissues of the oral cavity and pharynx. Positive results with certain carcinogens have, however, been obtained in the hamster cheek pouch. but it has also been pointed out that the cheek pouch lacks salivary glands and that its structure and func- tion differ from those of the oral mucosa. The majority of these studies are outlined in table A29. Although cigarette smoke condensate acts as a complete carcino- gen on mouse skin, the work of several authors (319) supports the concept that cigarette smoke contains cancer promoters that may be of special importance, particularly in orai carcinogenesis. Elzay (90) has reported that whole cigarette smoke is a promoting agent for the hamster cheek pouch. More importantly, regarding the chewing of tobacco, Bock, et al. (27,30), Van Duuren, et al. (29:), and Wynder and Hoffmann (321) have shown that unburned to- bacco products contain tumor promoters that might contribute to the promoting activity of the smoke. Roth, et al. (226, ,R.H') have shown that the dye-binding capacity of the DNA of oral epithelial cells is significantly enhanced in cigarette smokers in contrast to nonsmokers, probably reflecting an increase in the DNA content of oral epithelial cells in smokers. Smokers had values of dye-binding capacity intermediate between nonsmokers and 21 patients with proven oral cancer. Those smok- ers who refrained from smoking for up to six months showed a significant decrease toward more normal values. 314 I. Epidemiological and experimental studies contribu:e to the conclusion that smoking is a significant factor in the development of cancer of the oral cavity and that pipe smoking, alone or in conjunction with other forms of tobacco use, is causali>- related to cancer of the lip. 2. Experimental studies suggest that tobacco estracts and tobacco smoke contain initiators and promoters of cancerous changes in the oral cavity. CANCER OF THE ESOPHAGUS Esophageal cancer accounted for 4,306 deaths among -American males in 1967 and 1,321 deaths among females. The death rate from esophageal cancer has remained relatively constant since 1949. EPIDEMIOLOGICALSTUDIES The major prospective epidemiological studies (table 30) have indicated a significant relationship between smoking and esopha- geal cancer. Overall mortality ratios for male cigarette smokers range from 1.73 to 6.17. There are insufficient data concerning females for establishing firm conclusions. A number of retrospective studies concerning the relationship of smoking and esophageal cancer are outlined in table A31 and A31a. Smokers incur risk ratios ranging from 1.3 to 6.6 when compared with nonsmokers. As in studies of oral cancer, the effect of alcohol consumption must be taken into account in studies of esophageal cancer. Because a relationship between alcohol consumption and tobacco use is known to exist, \Vynder and Eross (810) analyzed the association between tobacco consumption and esophageal cancer after adjust- ing for alcohol intake. They found that in the absence of alcohd consumption, there was no association between the use of tobacco and esophageal cancer but that in the presence of alcohol consump- tion, an increasing relative risk with increasing number of ciga- rettes smoked \vas apparent, as well as an association bet\\-een cigar and pipe smoking and esophageal cancer. More recently, Takano, et al. (wz?), in a retrospective study of 3-00 patients with esophageal carcinoma, found an increased risk with smoking which was magnified by increased alcohol consump- tion. Martinez (28.7) analyzed the association of tobacco usage and esophageal cancer after controliing for age, sex, and alcohol consumptioir. Increasing relative risks with increasing tobacco use 315 TABLE 30.-Esophageal cancer mortdity ratios--prospective studies (Actual number of deaths shown in puenthnn)' SM = Smokera. NS = Nonsmokcn. Author, Number of ye.70 Nu,rn;:r;nd Data FOllOW. esophnae&\ countlY. collection UP yenn cllnccr Cigarette3/dny Pip-, CigIrl Commcntd rtfcrenee DoQulntlon deaths Hammond 187,783 white Quutionnairc 3 % 34 Cigarette amokcra Pipe hftied De.tn rcfcrring to and malts in 3 and follow.up NS 1 16133. z/33 cigarette mortality ratios Horn, State K&69 of death sar , 33 Cigar amokera Included cancer lOS8. ye*n of age. ccrtiflcate. 2133 13/K! al mouth U.S.A. and larynx. (190). Doll and Approximately Questionnaire 10 29 ~11 amokera bu amount tPipe and ciuar t Includes ex- Hill, 41.000 mnlc and follaw.u~ in yramr NS . . * 1.00 amaker, of pipe 1964, British of death NS . ,. 1,. 1.00 Shf . 2.00 and cigara, Great physicians. certificate. l-14 . . . . 2.00 Britrln IS-24 ,.., 3.60 (74). >25 . . 6.00 All . ., . 3.00 Kahn U.S. male Questionnaire E?`r 111 NS . . . . . l.OO(ll) Pipe t Rcfrra to (Ihrll). Yt-tel'B"9 and follow-up NS . ..I1 t1-9 . . 1.76 (2) 1.99 (3) cigarette 1966, 2.265.674 of death SM . ..lOO lo-19 . . . . 4.71(18) Cigar smokinl U.S.A. person yearn. certlflcate. 20-39 ., .11.60(24) 6.33(12) only. (139). >25 . . 7.65 (3) All . . . 6.17(47) Hammond, 440.55R male8 Interview by 4 46 NS .., . 1.00 (6) Pipe und CiQa.r 1966. 662.671 females ACS volunteers. NS ,.. 6 Shl (iire NS .._. 1.00 U.S.A. 35-84 YCBT9 or Shf 40 St4 I... 3.97(14) 45-60 4.17(32) (IIS). we in 26 States. Shl (age 65-79) 1.74 (81 TABLE SO.--Esophageal cancc?' Ino,`talitu rafios-p,`ospcctiuo studies (cont.) (Actual number of dcnthr shown in w.rcnthcs<%) Shl= Smokers, NS = Nonamokrrs. Author YCDT. country, Nuttny;nd Datn FQllOW- collection "II YCQl-3 Comments relercncc populntiun Hirnynms. 265,118 male Trained PIiS l',`r Slil _, 21 NS . . .., 1.U,O(D30 . . ., 1.82 (306). All ,. . 1.82 1 Unlcso otherwise epcciflcd. disparities between the totnl number of drolhs and the rum of the individual smoking cntegoriee are due to the exclwion of either occnsional, misceUnneoue. mixed, or ex-amokcrs. were noted. The consumption of very hot beverages was also found to be related to the development of esophageal cancer. PATHOLOGGIL STUDY Autopsy studies of smokers as compared with nonsmokers, spe- cifically observing the pathological changes in esophageal tissue, have been performed by Anerbach, et al. (15). A microscopic study was made of 12,598 sections of esophageal autopsy tissue from 1,268 men who died from causes other than esophageal cancer. The findings were strikingly similar to the abnormalities generally ac- cepted as representing premalignant tissue changes in the respira- tory tract epithelium. Esophageal epithelial cells with atypical nuclei (having an irregular distribution of chromatin) were found far more frequent.ly in cigarette smokers than in nonsmokers. Basal cell hyperplasia and hyperactive glands were also found more fre- quently in cigarette smokers than in nonsmokers. An increase in frequency with amount of cigarette smoking was noted for both epithelial cells with atypical nuclei and basal cell hyperplasia. Tables A32 and A33 summarize these findings. EXPERIMENTALSTUDIES Kuratsune, et al. (156) investigated the possibility that the car- cinogens known to be present in tobacco smoke could penetrate the esophageal epithelium more readily if dissolved in aqueous ethanol. Mice were exposed to several compounds by esophageal intubation. Tissues were then removed and studied by fluorescence microscopy. Deeper penetration and a different distribution were found when B[a]P was dissolved in aqueous ethanol as compared to B[a]P in olive oil. It was also found that benzo[a] anthracene and fluoran- thene dissolved in ethanol solution or aqueous caffeine solution could penetrate the epithelium of the esophagus. Horie, et al. (132) reported on the development of 10 papillomas and one squamous cell carcinoma of the esophagus in a group of 63 mice periodically forced to drink a solution of benzo[a]pyrene dissolved in diluted ethanol. Twenty-six papillomas and one squam- ous cell carcinoma also developed in a group of 63 mice to which 4-nitroquinoline l-oxide was administered in the same way. None of the 6'7 control animals given only diluted ethanol developed neoplasms. Several other authors have reported nitrosamine-induced esopha- geal cancer in experimental animals (56, 79, 80, 81). As noted above, the presence of nitrosamines in cigarette smoke is still a subject of debate. 318 1. Epidemiological studies ha\-e demonstrated that cigarette smoking is associated rvith the development of cancer of the esopha- gus. The risk of developing esophageal cancer among pipe and;or cigar smokers is greater than that for nonsmokers and of about the same order of magnitude as for cigarette smokers, or perhaps slightly lower. 2. Epidemiological studies have also indicated an association be- tlveen esophageal cancer and alcohol consumption and tthat alcohol consumption may interact with cigarette smoking. This combina- tion of exposures is associated with especially high rates of cancer of the esophagus. CANCER OF THE URISXRY BLADDER AND KIDNEY EPIDEMIOLOGICALSTUDIES (BLADDER) Cancer of the urinary bladder accounted for 6,019 deaths among American males and 2,743 deaths among American females in 1967 (289). Incidence rates have increased from 1949 to 1962 (88), but the death rates from bladder cancer have remained relatively stable during that period. Improvements in early diagnosis and therapy may have masked the increasing incidence of this disease. A number of epidemiological studies have indicated that smokers have an increased risk of contracting or of dying from bladder cancer (see tables 31 and A3.5). Certain of these studies include kidney cancer mortality in the results. The major prospective stud- ies, with the exception of that of British physicians, have shown bladder cancer mortality ratios among cigarette smokers ranging from 1.40 to 2.89. Smokers of more than 1 pack per day were shown to incur ratios of 3.12 to 5.41. The study by Doll and Hill (74, 75) of British physicians, on the other hand, reports death rates for smokers to be lower than those of nonsmokers based on 38 bladder cancer deaths. The mortality ratios for pipe or cigar smokers are substantially loxver than those among cigarette smokers. Pipe smokers were shown by both Hammond and Horn (120) and Kahn (13.9) to incur ratios approximating 1.50. Retrospective studies (table A35a) have also shown an increased proportion of smokers among bladder cancer patients when com- pared with matched controls. Relative risk ratios for bladder can- cer among smokers range from 1.0 to 7.3 among a11 smokers and up to 10.3 among heavy smokers of all types. 319 u N 0 TABLE 34.-Kidncu ami urinnru blatldcr cancer-prospective studies--Mortalit2/ ratios (~ctunl numlcr uf dcutha shown in ~~nrcnthescs)' Shl = Smokers. NS = Nonsmukcis. Author, )`car. Number and Data FCIIIOW. Number CO"lllTY, type Of collection "I, years of Cignretle/day Pipe. cigar Kidney Blnddcr Commcnta refcrcnce wl,ulation denlhs Hnmmund 187,183 white Questionnaire 3% 287 NS ,. 1.00(B) Pipe snd malen in 9 and 20 ,.. 3.42((l) Cipar U.S.A. NS ..l.O0(3R) (100). Shl , ..l.OG(I'i) Doll snd AnDroximatelv Questionnaire 10 38 NS . ..I.00 llill. 41,000 mule and follow. Sht ,O.dl 11c4. Llritish ua of death Crest Dhyeicinns. certificate. nritain (fb). All Sdf bv amount in ~rcarnn NS ..I.00 1-14 .0.69 16-24 . .o.c5 >25 .0.76 All I. .O.?l BCSl, Apuroximntelr Questionnaire 10 114 NS . 1.00 Pipe Rcfcrr to 1966. 18.000 mall? nnd follow- 30 .,. 1.43(16) Cigar gruu*. All ,. 1.40(10) NS . ..I.00 SM . ..1.16 (3) Hsmmond, 440,568 mules Interviews by 4 Bladder Cioarcllrc CiQCl'ClfCl hfnlc dn1n OlllY. 1966, 6GZ.G7 I ACS 13R NS ,I . . .I .* .1.00(22) 1.00(23) Blwhlcr IncluilM U.S.A. females volun1eere. SM ,116 SM (age 45-64) . ..1.42(64) Z.OO(GCJ) olher urinary (II(i). 35-R4 years NS . 23 SFll (nse 65-78) . ..1.5'7(?8) 2.96(66) tract COnLECrI. of ace in 25 Ridmu SLllbX. 104 Shl 82 NS 22 AUtllUr. yc)Lr. Nyne'yd Dnta Follow- Number roun1ry, c011cct10n "V yenre rcfcrcncc population de% Ciuarette/day Knhn U.S. nlRlc Questionnaire a',/. B!addcr (Darn), vcte:ana nnd follow. 224 196C, 2.266,674 "P of denth Shl 172 U.S.A. person certificate. NS . 62 (139). years. Kld,lcy 141 Shl ,102 NS 93 Pipe, CiBfit Kidney Bladder Comnlcnta - NS ,, ,, ,,, ,,,. .1.00(39) I'irle _. ., ,, ,. .1.32 (6) Cignr .,.. ,. .,.,. ..0.77 (6) CiKarettes/duy: l-9 ..I ,,,.... 0.97 (4) IO-19 ,...,.,.... 1.34121) 20-30 . . . . . . . .l.GB(lG) >39 .,,. ,,, ,. . ..2.76 (6) All ,.,.,... l.IG(IC) 1.00(62) Dladder includca 1.20 (8) other urinnry 0.94(10) tract CLIIICCIY. 1.10 (6) 1.93(37) 9.20(u) 2.52 (6) 2.1G(B?) - Hlraunmn. 2GG.110 mnlc Trnincd PIIS 1 `ii SM C NS 1.00 rllnddcr cn>>ccr only. lOG7. nnd fcmnle nurse intcr- Shl .lO.OO (6) ncrcm to ali Japnn adults 40 view and inrmr of swokinu. (IPJ). YCLlM of nge foilow-up nnd older. of dcnth ccrlificnte. Weir and 68.163 males Qucstionnalre 6-8 Biaddcr NS .x.1.00 NS . ..l.OO ShI include. ex- Dunn. in vnrious and follow- 27 ?lO ..0.6G 210 , . .1.82 smokcra. 1970, occupations UP of dcnth Kidmu -c20 .3.30 -e20 . .2.81 NS include ~ipc U.S.A. In California. ccrtilicnte. 27 >30 . .2.67 >30 . .6.41 snd clgor (306). All . .2.40 All . .2.89 amakcra. `Unless othrrwivc spccificd. dirpnrities between the total number of drnths nnd the sum of the individual smoking categories are due to the exclusion of rithcr occnsianal, miscelloneoua. mixed. or ex-smokers. W h, Y EPIDEMIOLOGICALSTUDIES (KIDYEY) A total of 5,53-1 Americans died of cancer of the kidney durir.:: 1967. A relationship between smoking and this type of cancer has been suggested by several epidemiological studies. The three major studies which separately examine the relationship of kidney cancer to smoking (table 34), namely those of Hammond (I I&), Kahn (139), and Weir and Dunn (~`06)~ have shown mortalit>- ratios for all cigarette smokers to range from 1.43 to L-16. Retrospective studies by Bennington, et al. (18, 13) have indicated a signilicant association between all forms of smoking and renal adenoma and adenocarcinoma. Numerous experiments have been undertaken by many invtsti- gators to elucidate the relationship of tobacco smoking to bladder carcinogenesis. The two areas of major concern have centered upon the presence of a known bladder carcinogen, beta naphth>-lam:ne. in cigarette smoke and the presence of abnormal tryptophan me- tabolism in patients with bladder cancer. By virtue of data gathered concerning industrial exposure of workers, beta naphthylamine has long been kno\vn as a bladder carcinogen. Complementing such data was the work of Hueper, et al. (136) who subjected mongrel dogs to daily subcutaneous injec- tions and oral administration of commercial beta naphthylamine. Thirteen of the 16 animals developed bladder papillomas and c21-- cinemas of the bladder. Saffiotti, et al. (236) fed hamsters a diet containing up to 1.0 percent beta naphthylamine and observed that 18 of 39 animals developed bladder tumors, almost all typical tran- sitional cell carcinomas. More recently, Conzelman, et al. (59) ad- ministered beta naphthylamine to 24 rhesus monkeys for more than 30 months. Transitional ceil carcinomas of the urinary biad- der were induced in 9 of the animals, and a dose-response relation- ship was apparent. Pailer, et al. (207) and Miller and Stedman (183) failed to End this amine in cigarette smoke. However, more recently, Hoffmann, et al. (127) identified it in cigarette smoke. The authors, noting the minute quantity present in each cigarette (2.2 x 10--g), hesi- tated to attach a biological significance to the finding. Of more recent interest have been the metabolites of tr>-ptophan present in certain patients with bladder cancer. A number of nor- mal and abnormal metabolites of tryptophan have been found to be carcinogenic when tested by implantation in the bladders of mice. These include 3-hydroxykynurenine (OHKy), 3-hy-droxyanthranilic 322 acid (OHA), 3-hydroxy-%-amino-acetophenone (all orthoamino- phenols), the S-methyl ether of santhurenic acid (CHSa), santhu- renic acid (,Ya), I>-kynurenine (KY), quinnldic acid, and Zmeth- oxyanthranilic acid (3CHO.1) (2, 36, 37, 39, $7, $8). OHKy and OHX are frequently present in human urine, as is kynurenic acid (KYA). Certain investigators have concentrated their attention on the presence of abnormal tryptophan metabolites and increased amounts of normal tryptophan metabolites in the urine of patients with bladder cancer as compared with selected controls (1, 40, $6, 97, 118, 214,243, 329). These authors have observed the increased excretion of Ky, KyA, OHKy, anthranilic acid, OHA, and acetylky- nurenine in such patients. Yoshida, et al. (329), in a recent study concerning the relationship between tryptophan metabolism and heterotopic recurrences of human urinary bladder tumors, reported that those patients with recurrences showed abnormal metabolite excretion more often than those without recurrences. The relationship of smoking to these biochemical findings is presently uncertain. Kerr, et al. (1$3), in 30 experiments on 3 smokers and 3 nonsmokers who were given large doses of trypto- phan, found that smoking increased the urinary excretion of OHKy and OHA and decreased that of N'methylnicotinamide (an end product of tryptophan metabolism). Kerr concluded that smoking interferes with the normal metabolism of tryptophan. Recently, Brown, et al. (45) studied 15 adults under smoking and abstinence conditions and found that except for the basal escretion of acetylky- nurenine, tryptophan metabolite excretion did not change with smoking or cessation. The authors also compared 13 nonsmokers and 17 regular cigarette smokers under basal and tryptophan- loaded conditions. No differences were observed in the excretion of the measured tryptophan metabolites. However, due to its instabil- ity, OHA was not measured. The authors concluded that the rela- tionship of smoking to urinary bladder cancer was probably not vk - - its effect on the kynurenine pathxvay of tryptophan metabolism. Another experimental approach to the relationship of smoking and urinary bladder cancer is reflected in the work of Schlegel, et al. (2: :, 2:~). The authors observed an elevated concentration of certain ortho-amincphenols in the urine of bladder cancer patients and cigarette smokers, when compared with nonsmokers (245). More recently (?$5), the same group compared the chemilumines- cence of the urines of smokers, nonsmokers, and bladder tumor patients. They noted that nonsmokers showed the lowest level of luminescence (\vhich they relate to the presence of aromatic hydi-o- carbons) and the bladder tumor patients the highest level. The normal cigarette smokers' level was found to be intermediate. 323 Hnmmond 440.55n nl?.lPJ Inlcrvicws by 1OGG `56?.671 Irmnh ACS U S.A. JG-WI ycn1'3 volunteers (Ira). of nge in 26 Kahn (Don) 1966 U.S.A. (139). 4 262 S&l . ..233 NS .., 20 8:; 344 tshl 1 ,ZSG NS 68 _.~. NS . ...% 1.00 (29) Shl (WC 4644) 2.63 ( 168) Shl (RBC hlnlc dsln only. 65-79) 2.17 (76) NS ,.,.. 1.00 (88) 1-I 0.87 (81 LO-20 1.93 (65) 21-31 2.18 (43) >no ..I 1.87 (7) All ..I 184(125) Piwa t ~lrferr to current amok= NS ..1.00(88) or .II (YDCJ. Shl ..0.74 (8) Cipar8 NS .1.00(88) Shl a .1.5?(27) rIotI, NS .l 00(H) Shl .0.93(13) Iiirnrnmn. 2G5,llX InrllC Tmincd PllS 1 `,`1 Shl ,, I4 NS ,, 1.00 I (PI., THOMAS, G. M. Bladder tumours and smoking. Interna- tional Journal of Cancer 5(Z) : 266272, March 15, 1970. (C) ARlilS, A.. WAGNER, D. H. Primary carcinoma of the lung. A diagnostic study of one hundred and thirty-five cases in 4 years. Journal of the American Medical Association 106(8) : 587-591, February 22, 1936. 325