Occupation and lung cancer risk. An analysis by histologic subtypes

Asbestos exposure and small cell lung cancer: Systematic review and meta-analysis

Asbestos is a mineral that is carcinogenic to humans. Its use has been banned in many occidental countries yet it is still produced in the United States, and materials that contain asbestos remain in many occupational settings and indoor environments. Even though asbestos carcinogenicity is well known, there is scant literature on its specific effects regarding small cell lung cancer (SCLC). We therefore conducted a systematic review and meta-analysis to determine SCLC risk among workers exposed to asbestos. A systematic search of the literature was conducted to identify studies which reported occupational exposure to asbestos and SCLC-related deaths and/or incidence. We identified seven case-control studies that included 3,231 SCLC cases; four studies reported smoking-adjusted risks. A significantly increased risk of SCLC (pooled OR 1.89; 95% CI, 1.25-2.86) was observed on pooling studies on men (six studies) that displayed moderate heterogeneity (I2 = 46.0%). Overall, our synthesis suggests that occupational exposure to asbestos significantly increases the risk of SCLC on men.

Health effects associated with smoking: a Burden of Proof study

As a leading behavioral risk factor for numerous health outcomes, smoking is a major ongoing public health challenge. Although evidence on the health effects of smoking has been widely reported, few attempts have evaluated the dose-response relationship between smoking and a diverse range of health outcomes systematically and comprehensively. In the present study, we re-estimated the dose-response relationships between current smoking and 36 health outcomes by conducting systematic reviews up to 31 May 2022, employing a meta-analytic method that incorporates between-study heterogeneity into estimates of uncertainty. Among the 36 selected outcomes, 8 had strong-to-very-strong evidence of an association with smoking, 21 had weak-to-moderate evidence of association and 7 had no evidence of association. By overcoming many of the limitations of traditional meta-analyses, our approach provides comprehensive, up-to-date and easy-to-use estimates of the evidence on the health effects of smoking. These estimates provide important information for tobacco control advocates, policy makers, researchers, physicians, smokers and the public.

Prevalence of occupational exposure to asbestos and crystalline silica according to phenotypes of lung cancer from the CaProMat study: A case-only study

BACKGROUND

The objective of the study was to compare the prevalence of occupational exposure to asbestos and crystalline silica according to histological types of lung cancer and age at diagnosis.

METHODS

CaProMat study is a pooled case-only study conducted between 1996 and 2011. The current study consisted of 6521 lung cancer cases. Occupational exposure to asbestos and crystalline silica was assessed by two Job-Exposure Matrices. A weighted prevalence of exposure was derived and compared according to histological types and age at diagnosis.

RESULTS

There was no difference of weighted prevalence of exposure to asbestos and crystalline silica according to histological types of lung cancer. There was a statistically significant difference of weighted prevalence of exposure to asbestos and crystalline silica according to age at diagnosis.

CONCLUSIONS

Due to the limited clinical importance of the difference, neither the histological type, nor the age at diagnosis can be used as an indicator for the occupational exposure to asbestos or crystalline silica.

Systematic review with meta-analysis of the epidemiological evidence in the 1900s relating smoking to lung cancer

BACKGROUND

Smoking is a known lung cancer cause, but no detailed quantitative systematic review exists. We summarize evidence for various indices.

METHODS

Papers published before 2000 describing epidemiological studies involving 100+ lung cancer cases were obtained from Medline and other sources. Studies were classified as principal, or subsidiary where cases overlapped with principal studies. Data were extracted on design, exposures, histological types and confounder adjustment. RRs/ORs and 95% CIs were extracted for ever, current and ex smoking of cigarettes, pipes and cigars and indices of cigarette type and dose-response. Meta-analyses and meta-regressions investigated how relationships varied by study and RR characteristics, mainly for outcomes exactly or closely equivalent to all lung cancer, squamous cell carcinoma ("squamous") and adenocarcinoma ("adeno").

RESULTS

287 studies (20 subsidiary) were identified. Although RR estimates were markedly heterogeneous, the meta-analyses demonstrated a relationship of smoking with lung cancer risk, clearly seen for ever smoking (random-effects RR 5.50, CI 5.07-5.96) current smoking (8.43, 7.63-9.31), ex smoking (4.30, 3.93-4.71) and pipe/cigar only smoking (2.92, 2.38-3.57). It was stronger for squamous (current smoking RR 16.91, 13.14-21.76) than adeno (4.21, 3.32-5.34), and evident in both sexes (RRs somewhat higher in males), all continents (RRs highest for North America and lowest for Asia, particularly China), and both study types (RRs higher for prospective studies). Relationships were somewhat stronger in later starting and larger studies. RR estimates were similar in cigarette only and mixed smokers, and similar in smokers of pipes/cigars only, pipes only and cigars only. Exceptionally no increase in adeno risk was seen for pipe/cigar only smokers (0.93, 0.62-1.40). RRs were unrelated to mentholation, and higher for non-filter and handrolled cigarettes. RRs increased with amount smoked, duration, earlier starting age, tar level and fraction smoked and decreased with time quit. Relationships were strongest for small and squamous cell, intermediate for large cell and weakest for adenocarcinoma. Covariate-adjustment little affected RR estimates.

CONCLUSIONS

The association of lung cancer with smoking is strong, evident for all lung cancer types, dose-related and insensitive to covariate-adjustment. This emphasises the causal nature of the relationship. Our results quantify the relationships more precisely than previously.

Relationships between lung adenocarcinoma and gender, age, smoking and occupational risk factors: A case-case study

BACKGROUND

The hypothesis that some risk factors for lung cancer may have more specific associations with particular histologic types remains controversial. The aim of this study was to investigate possible associations between adenocarcinoma and gender, age, smoking characteristics and selected occupational carcinogens in relation to other histologic types.

METHODS

This study included all histologically confirmed lung cancer cases diagnosed consecutively in two French University hospitals from 1997 to 2006. All medical data were obtained by face-to-face patient interviews. Occupational carcinogen exposures of each patient were assessed by an industrial hygienist. Relationships between risk factors and adenocarcinoma were analyzed by case-case comparisons using unconditional logistic regressions (ULRs).

RESULTS

A total of 1493 subjects were enrolled in this study, comprising 1303 men (87.3%), 67 nonsmokers (4.5%) and 489 adenocarcinomas (32.7%). Using ULR, no associations were observed between adenocarcinoma and age, gender or smoking characteristics except for a negative relationship with smoking duration (p<0.0001). Significant associations were observed between ADC and exposure to welding fumes and silica in the whole population and with polycyclic aromatic hydrocarbons in ever smokers.

CONCLUSION

This study demonstrated that some risk factors, such as duration of smoking and certain occupational exposures but not gender or age, have a more important influence on the incidence of lung ADC than on other histologic types. As the distribution of histologic types may reflect underlying biological mechanisms, these findings also suggest that lung carcinogenesis pathways should be studied in relation to smoking duration and other lung cancer risk factors.

Identification of occupational cancer risk in British Columbia: a population-based case-control study of 2,998 lung cancers by histopathological subtype

BACKGROUND

Few studies have investigated occupational lung cancer risk in relation to specific histopathological subtypes.

METHODS

A case-control study was conducted to evaluate the relationship between lung cancer and occupation/industry of employment by histopathological subtype. A total of 2,998 male cases and 10,223 cancer controls, diagnosed between 1983 and 1990, were identified through the British Columbia Cancer Registry. Matched on age and year of diagnosis, conditional logistic regression analyses were performed for two different estimates of exposure with adjustment for potentially important confounding variables, including tobacco smoking, alcohol consumption, marital status, educational attainment, and questionnaire respondent.

RESULTS

For all lung cancers, an excess risk was observed for workers in the primary metal (OR = 1.31, 95% CI, 1.01-1.71), mining (OR = 1.53, 95% CI, 1.20-1.96), machining (OR = 1.33, 95% CI, 1.09-1.63), transport (OR = 1.50, 95% CI, 1.08-2.07), utility (OR = 1.60, 95% CI, 1.22-2.09), and protective services (OR = 1.27, 95% CI, 1.05-1.55) industries. Associations with histopathological subtypes included an increased risk of squamous cell carcinoma in construction trades (OR = 1.25, 95% CI, 1.06-1.48), adenocarcinoma for professional workers in medicine and health (OR = 1.73, 95% CI, 1.18-2.53), small cell carcinoma in railway (OR = 1.62, 95% CI, 1.06-2.49), and truck transport industries (OR = 1.51, 95% CI, 1.00-2.28), and large cell carcinoma for employment in the primary metal industry (OR = 2.35, 95% CI, 1.11-4.96).

CONCLUSIONS

Our results point to excess lung cancer risk for occupations involving exposure to metals, polyaromatic hydrocarbons and asbestos, as well as several new histopathologic-specific associations that merit further investigation.

After Helsinki: a multidisciplinary review of the relationship between asbestos exposure and lung cancer, with emphasis on studies published during 1997-2004

Despite an extensive literature, the relationship between asbestos exposure and lung cancer remains the subject of controversy, related to the fact that most asbestos-associated lung cancers occur in those who are also cigarette smokers: because smoking represents the strongest identifiable lung cancer risk factor among many others, and lung cancer is not uncommon across industrialised societies, analysis of the combined (synergistic) effects of smoking and asbestos on lung cancer risk is a more complex exercise than the relationship between asbestos inhalation and mesothelioma. As a follow-on from previous reviews of prevailing evidence, this review critically evaluates more recent studies on this relationship--concentrating on those published between 1997 and 2004--including lung cancer to mesothelioma ratios, the interactive effects of cigarette smoke and asbestos in combination, and the cumulative exposure model for lung cancer induction as set forth in The Helsinki Criteria and The AWARD Criteria (as opposed to the asbestosis-->cancer model), together with discussion of differential genetic susceptibility/resistance factors for lung carcinogenesis by both cigarette smoke and asbestos. The authors conclude that: (i) the prevailing evidence strongly supports the cumulative exposure model; (ii) the criteria for probabilistic attribution of lung cancer to mixed asbestos exposures as a consequence of the production and end-use of asbestos-containing products such as insulation and asbestos-cement building materials--as embodied in The Helsinki and AWARD Criteria--conform to, and are further consolidated by, the new evidence discussed in this review; (iii) different attribution criteria (e.g., greater cumulative exposures) are appropriate for chrysotile mining/milling and perhaps for other chrysotile-only exposures, such as friction products manufacture, than for amphibole-only exposures or mixed asbestos exposures; and (iv) emerging evidence on genetic susceptibility/resistance factors for lung cancer risk as a consequence of cigarette smoking, and potentially also asbestos exposure, suggests that genotypic variation may represent an additional confounding factor potentially affecting the strength of association and hence the probability of causal contribution in the individual subject, but at present there is insufficient evidence to draw any meaningful conclusions concerning variation in asbestos-mediated lung cancer risk relative to such resistance/susceptibility factors.

Smoking status, occupational asbestos exposure and bronchial location of lung cancer

The objective of this study was to determine the factors associated with central airway versus peripheral bronchial location of lung cancer. All patients diagnosed with lung cancer from 1997 through 2000 in the Respiratory Disease Department of Rouen University Hospital were prospectively interviewed about their smoking and occupational history using a standardized questionnaire. All patients underwent white-light bronchial endoscopy using a 4.5 mm flexible endoscope. Tumors were classified as central when they were accessible and visible using this technique. Out of 217 cases of lung cancer included in this study, 155 (71%) were central. Histological type of lung cancer was strongly associated with bronchial location as central location was observed in 48, 82 and 92% of Adenocarcinoma (AC), Squamous Cell (SqC), and Small Cell Carcinoma (SCC), respectively (P<0.0001). Among non asbestos-exposed patients, location varied little with smoking status, with central location frequency ranging from 74 to 80%. In contrast, lung cancer was recorded central in 41% of long-term (> or =10 years) ex-smokers, 67% of short-term (<10 years) ex-smokers and 75% of current smokers (P=0.04) among patients exposed to asbestos, suggesting an interaction between duration of smoking cessation and occupational asbestos exposure with respect to lung cancer location. These findings were confirmed after adjustment for sex, age and histologic type in multivariate analysis. These results suggest that individually-tailored multimodality screening strategies relying on various combinations of low-dose CT scan, sputum analysis and fluorescence endoscopy according to each patient's profile may be more effective than standard strategies based on a single approach for all patients.

Characteristics of patients with lung cancer under the age of 45 years: a case control study

OBJECTIVE

The aim of this study was to define the clinical and pathological features associated with lung cancer diagnosed in persons under the age of 45 compared with lung cancer in an older population of greater than 45 years.

METHODOLOGY

A case control study was undertaken. Cases were defined as patients diagnosed with lung cancer under the age of 45 years. Controls were lung cancer patients over 45 years matched only for the date of diagnosis. Up to four controls were selected for each case. A retrospective review was undertaken of the records of a single tertiary respiratory institution which served a population of 1.2 million.

RESULTS

Forty-eight cases of lung cancer (< 45 years of age) were identified and were compared to 123 matched controls with lung cancer (> 45 years of age). Of the cases 67% were female compared with 32% female cases in the control group (P < 0.01). The rate of adenocarcinoma was significantly higher among cases (48% vs 27%, P=0.001), while squamous cell carcinoma was more common in the controls (35% vs 17% P =0.001). Smoking was common in both groups although less so among cases (79% vs 95%, P=0.001)). There was no difference in survival rates between the cases (11 months) compared with controls (8 months) (P=0.1).

CONCLUSIONS

Young lung cancer patients were predominantly female and adenocarcinoma accounted for a disproportionate number of the histological types. Cigarette smoking appears to be the main aetiological agent but as 21% of the patients under 45 years were non-smokers, other factors (genetic/hormonal) may also contribute. This study has not demonstrated a worse outcome in younger patients.

Effect of smoking cessation on major histologic types of lung cancer

STUDY OBJECTIVES

It is well-recognized that the risk of lung cancer declines after smoking cessation. However, the degree of decline in different histologic types of lung cancer is not well understood. We conducted a meta-analysis of peer-reviewed studies to assess the effect of smoking cessation on rates of major histologic types of lung cancer.

DESIGN

Studies published in English between 1970 and 1999 were identified through searches of computerized databases (ie, MEDLINE and CANCERLIT). Combined estimates of relative risk and 95% confidence intervals were calculated for 27 studies using fixed and random effects models. Separate analyses were conducted for men and women.

RESULTS

Smoking cessation was associated with a reduction in the risk of all the major histologic types of lung cancer. The highest reduction was in small cell lung carcinoma (SCLC) and squamous cell carcinoma (SQC), and the lowest reduction was seen in large cell cancer and adenocarcinoma. In women, the combined risks for SQC and SCLC were higher than those in men. The dose-response curve for intensity of smoking was steeper in women.

CONCLUSION

The findings of this study suggest that smoking cessation results in the greatest reductions for SCLC and SQC. This effect is most marked in heavy smokers, particularly among women.

Lung cancer in patients under age 40

A retrospective review of patients <40 years (n=91) seen at the Dana-Farber Cancer Institute and Brigham and Women's Hospital from January 1, 1983-January 1, 1993 was carried out. Of 91 patients, there were 43 men and 48 women with a median age of 36 years (range 28-39). Eighty percent of patients were cigarette smokers for a median of 25 pack years (range 2-68). Ninety-one percent were symptomatic at presentation. The ECOG performance status (PS) was 0 or 1 in 83%. At the time of diagnosis 15% had stage I/II, 17% stage IIIA, 22% stage IIIB and 45% stage IV disease. The most common histopathology was adenocarcinoma (46%), followed by small cell carcinoma (14%), squamous cell carcinoma (12%), large cell undifferentiated (8%) and other types (20%). The median survival for all 91 patients was 1 year with 2 and 5 year survivals of 30% and 18% respectively. Five year survival was related to stage of disease: 60% for patients with stage I, 58% for stage II, 36% for stage IIIA, 10% for stage IIIB, and 3% for stage IV disease. Factors that had no significant effect on overall survival included gender, histologic subtype, degree of differentiation, presence or absence of symptoms, and sites of metastases. Factors that adversely affected survival by univariate analysis included advanced stage of disease, poor PS, duration of symptoms for more than 3 months, and 5% or greater body weight loss. By multivariate analysis only stage (P<0.001) and weight loss (P=0.02) affected survival. This data plus results of other published studies show that young patients under age 40 with lung cancer, compared to the more common older patients, have an increased percentage of women, have a longer duration of symptoms, more often have adenocarcinoma with lower frequency of squamous cell carcinoma and sometimes small cell carcinoma, and more often present with advanced disease. Despite these differences, overall patient survival remains poor and is similar to that of older patients.

Effect of cigarette smoking on major histological types of lung cancer: a meta-analysis

Although cigarette smoking is an established risk factor for lung cancer, the strength of association with different histologic types is not well understood. This meta-analyses of peer-reviewed studies was conducted to assess the effect of cigarette smoking on major histologic types of lung cancer. Studies were identified through MEDLINE and CANCERLIT searches. A total of 48 studies published between 1970 and 1999 were identified. Combined estimates of relative risks (OR) and 95% confidence intervals (CI) were calculated using fixed and random effect models. Separate analyses were conducted by study design and gender. A linear dose-response was fit to studies reporting data on intensity and duration of smoking. All histologic types of lung cancer were significantly associated with cigarette smoking. The association was stronger with squamous cell carcinoma (SQC) and small cell carcinoma (SCLC) than with large cell cancer (LGC) and adenocarcinoma (ADC). The combined OR for heaviest smoking intensity (30+ cigarettes per day) ranged from 4.10 (CI 3.16-5.31) for ADC to 18.3 (CI 9.26-36.4) for SCLC. The combined OR for longest duration of smoking (40+ years) ranged from 3.80 (CI 2.35-6.16) for ADC to 38.6 (CI 11.9-125) for SCLC. In women, the combined OR for SQC and SCLC were higher than those in men. The dose response curve for intensity of smoking was steeper in women. The findings of this study provide additional evidence for a causal relationship between smoking and all histologic types of lung cancer.

Lung cancer in patients < 50 years of age: the experience of an academic multidisciplinary program

OBJECTIVE

To determine if the clinicopathologic features and survival of lung cancer patients < 50 years of age differ from those of older patients.

DESIGN

Retrospective review of patients with primary bronchogenic carcinoma diagnosed at a single, multidisciplinary cancer center.

SETTING

A National Cancer Institute-designated comprehensive cancer center in urban Detroit, MI.

PATIENTS

All patients with primary bronchogenic carcinoma evaluated in the Multidisciplinary Lung Cancer Clinic at the Barbara Ann Karmanos Cancer Institute between 1990 and 1993.

RESULTS

Of 1,012 patients with lung cancer, 126 (12.5%) were < 50 years old at diagnosis, with a median age of 44 years. The median age of the 886 patients > or = 50 years of age was 65 years. The gender (p = 0.08) and racial (p = 0.12) characteristics of the younger and older patient groups were not significantly different. More than 90% of patients in both groups were smokers. The incidence of adenocarcinoma was significantly higher in younger patients (48.4% vs 36.0%, p < 0.001), and early-stage disease was less frequently diagnosed in younger patients (4.8% vs 19.7%, p < 0.001). Younger patients were more likely than older patients to undergo treatment, including surgery and combined-modality therapy (p < 0.001). Median survival was 13 months in younger and 9 months in older patients, while overall survival was similar in younger and older patients (p = 0.13).

CONCLUSIONS

Although younger patients with lung cancer present with more advanced-stage disease, their overall survival is similar to that of older patients, suggesting that lung cancer is not an inherently more aggressive disease in patients < 50 years of age.

Cigarette smoking and changes in the histopathology of lung cancer

BACKGROUND

Adenocarcinoma of the lung, once considered minimally related to cigarette smoking, has become the most common type of lung cancer in the United States. The increased incidence of this cancer might be explained by advances in diagnostic technology (i.e., increased ability to perform biopsies on tumors in smaller, more distal airways), changes in cigarette design (e.g., the adoption of filtertips), or changes in smoking practices. We examined data from the Connecticut Tumor Registry and two American Cancer Society studies to explore these possibilities.

METHODS

Connecticut Tumor Registry data from 1959 through 1991 were analyzed to determine whether the increase in lung adenocarcinoma observed during that period could be best described by birth cohort effects (i.e., generational changes in cigarette smoking) or calendar period effects (i.e., diagnostic advances). Associations between cigarette smoking and death from specific types of lung cancer during the first 2 years of follow-up in Cancer Prevention Study I (CPS-I), initiated in 1959) and Cancer Prevention Study II (CPS-II, initiated in 1982) were also examined.

RESULTS

Adenocarcinoma incidence in Connecticut increased nearly 17-fold in women and nearly 10-fold in men from 1959 through 1991. The increases followed a clear birth cohort pattern, paralleling gender and generational changes in smoking more than diagnostic advances. Cigarette smoking became more strongly associated with death from lung adenocarcinoma in CPS-II compared with CPS-I, with relative risks of 19.0 (95% confidence interval [CI] = 8.3-47.7) for men and 8.1 (95% CI = 4.5-14.6) for women in CPS-II and 4.6 (95% CI = 1.7-12.6) for men and 1.5 (0.3-7.7) for women in CPS-I.

CONCLUSIONS

The increase in lung adenocarcinoma since the 1950s is more consistent with changes in smoking behavior and cigarette design than with diagnostic advances.

The influence of physical activity on lung-cancer risk: A prospective study of 81,516 men and women

Physical activity is inversely related to mortality from respiratory diseases including lung cancer. Physical activity improves pulmonary function but its impact on lung-cancer risk has not been studied much. During 1972-1978, 53,242 men and 28,274 women, aged 20 to 49 years, participated in a population-based health survey and were followed until 31 December 1991. We observed a total of 413 men and 51 women with lung cancer. Leisure activity and work activity were assessed using a questionnaire in 4 categories. In a sub-cohort, physical activity was assessed twice at an interval of 3 to 5 years. Leisure but not work activity was inversely related to lung-cancer risk in men after adjustment for age, smoking habits, body-mass index and geographical residence (p for trend = 0.01). Men who exercised at least 4 hours a week had a lower risk than men who did not exercise [relative risk (RR) = 0.71; 95% confidence interval (CI) = 0.52-0.97]. Reduced risk of lung cancer was particularly marked for small-cell carcinoma (RR = 0.59; 95% CI = 0.38-0.94) and for adenocarcinoma (RR = 0.65; 95% CI = 0.41-1.05), with no association seen for squamous-cell carcinoma. In the sub-cohort in which physical activity was assessed twice, the risk of lung cancer was particularly reduced among men who were most active at both assessments (RR = 0.39; 95% CI = 0.18-0.85). No consistent association between physical activity and lung-cancer risk was observed among women. Our results suggest that leisure physical activity has a protective effect on lung-cancer risk in men. The small number of incident cases, combined with the narrow range of physical activity reported, may have limited our ability to detect an association between physical activity and lung cancer in women.

Exposure to crocidolite and the incidence of different histological types of lung cancer

OBJECTIVES

To estimate the relations between exposure to both tobacco smoke and crocidolite and the incidence of various histological types of lung cancer.

METHODS

In 1979 all former workers from the Wittenoom asbestos industry who could be traced were sent a questionnaire on smoking history. Of 2928 questionnaires sent, satisfactory replies were received from 2400 men and 149 women. Of the men, 80% had smoked at some time and 50% still smoked. Occupational exposure to crocidolite was known from employment records and follow up was maintained through death and cancer registries in Australia with histological diagnoses obtained from the relevant State Cancer Registry. Conditional logistic regression was used to estimate the effects of tobacco and asbestos exposure on incidence of different cell types of lung cancer in a nested case-control design.

RESULTS

Between 1979 and 1990, 71 cases of lung cancer occurred among men in this cohort: 27% squamous cell carcinoma, 31% adenocarcinoma, 18% small cell carcinoma, 11% large cell carcinoma, and 13% unclassified or indeterminate. Two of the classified cases and one unclassified case had never smoked. The incidence of both squamous and adenocarcinoma types of lung cancer were greatest in ex-smokers and in those subjects with the highest levels of exposure to crocidolite. After adjustment for smoking habit, the increase in incidence of lung cancer with increasing exposure to crocidolite was greater for squamous cell carcinoma than for adenocarcinoma.

CONCLUSIONS

The results from this study have shown significant exposure-response effects for exposure to crocidolite, and both adenocarcinoma and squamous cell carcinoma of the lung. They also provide some further evidence against the theory that parenchymal fibrosis induced by asbestos is a necessary precursor to asbestos induced lung cancer.

[Occupational exposure and lung cancer in smokers]

High male lung cancer incidence and mortality in Rosario city, Argentina, have been found in previous studies. A project was undertaken for the purpose of evaluating the life-time occupational history as well as the duration and intensity of cigarette smoking as determinants of histologic cell types in 211 male patients with primary lung cancer. Their histologic cell types were: squamous 39%, adenocarcinoma 29%, small cell 18%, and others and not specified 14%. An association was found between histologic cell types and occupations (p < 0.0001), adenocarcinoma being more prevalent in office personnel, teachers, accountants, lawyers, and squamous in the other, supposedly dirtier working environments, mainly in those men who had begun to work in farming and later transferred to mechanics and metallurgy. These latter ones were diagnosed at a younger age than those in other occupations, with a significant difference for squamous and small cell. No differences in the smoking intensity were found between the occupational groups. The mean age these patients began to smoke at was 15 years for those with squamous and small cell, and 17 years for those with adenocarcinoma (p < 0.001). An interesting finding was the difference at their mean-age at diagnosis, 58 years for smokers and 68 for ex-smokers (p < 0.0001). Studies are needed to elucidate the interplay of risk factors in the etiology of histologic subtypes of lung cancer.

Occupation and lung cancer risk among women in northern China

Lifetime occupational histories were obtained in a case-control study of 965 female lung cancer patients and 959 controls selected from the general population in Shenyang and Harbin, People's Republic of China, where most women have worked outside the home. After adjusting for smoking, we found a significantly increased risk of lung cancer associated with employment involving the manufacture of transportation equipment (OR = 1.6, 95% CI = 1.0, 2.6), in particular the manufacturing of automobiles (OR = 3.0, 95% CI = 1.4, 6.4). Metal smelting and treatment workers were at an increased risk of lung cancer (OR = 1.5, 95% CI = 1.0, 2.1); the highest risks were observed among metal surfacers (OR = 3.1, 95% CI = 1.1, 9.0) and currently employed foundry workers (OR = 13.0, 95% CI = 1.7, 99.4). On the other hand, about a 50% decreased risk of lung cancer was observed among those employed in textile industries or as leaders of state and party organizations. Based on self-reports, exposures to coal dust and smoke from burning fuel at the workplace were also significant risk factors. The findings were similar when the analyses were confined to nonsmokers and were comparable across the major cell types of lung cancer.

Lung cancer: a prospective study of smoking, occupation, and nutrient intake

A cohort study of lung cancer was conducted among 7,961 Japanese-American men who were interviewed and examined during 1965-1968. Information was collected about their smoking history, occupation, and nutrient intake. After 22 y, 227 incident cases of lung cancer were identified. Cigarette smoking significantly increased lung cancer risk. The relative risk (RR) was 3.1 for past smokers and 11.4 for current smokers, compared with never smokers. We separated lung cancer cases according to histological type, and it was found that current smokers had a RRs of 16.0 for squamous/small-cell carcinoma and 6.8 for adenocarcinoma of the lung. Unskilled manual workers had a significantly higher risk (RR = 1.5; 95% confidence interval, 1.1-2.2) for lung cancer than workers who were engaged in nonmanual occupations. There was no association between lung cancer and the 24-h intake of total calories, protein, fat, dietary cholesterol, carbohydrates, and alcohol, but this may have resulted from the limitations of a 24-h dietary questionnaire.

Effect of occupational air pollutants on various histological types of lung cancer: a population based case-control study

A population based case-control study was performed in Cracow, Poland, to determine the effect of occupational air pollutants on various histological types of lung cancer. Male cases and controls were identified from the Cracow Death Register. Information was obtained by mailed questionnaire from next of kin on smoking, occupational branch, occupational exposures, and other pertinent variables. Response rates were 73.5% in cases and 72.0% in controls. For cases that underwent a bronchial biopsy or surgical excision the histological diagnosis of the tumour was obtained from clinical records. The case group contained 343 subjects with squamous cell carcinomas, 151 with small cell carcinomas, and 106 with adenocarcinomas. Twenty seven cases showed other histological types (large cell carcinoma and not classifiable). Analysis was performed separately by histological type for occupational exposure variables adjusted for smoking. Long term exposure to mineral dust and metal dust (20 years or more) was found to be a significant risk factor for small cell and squamous cell carcinoma. The effect was more pronounced if the analysis was restricted to those aged less than 70 years. The highest relative risk (RR) due to occupational exposures was found for squamous cell carcinoma and exposure to mineral dust for more than 20 years (RR = 2.45, 95% CI 1.43-4.19). The estimated effect of mineral dust on small cell carcinoma and adenocarcinoma was smaller (RR = 2.29, 95% CI 1.16-4.53 and RR = 2.04, 95% CI 0.89-4.64 respectively). The effect of metal dust and fumes seemed about the same for squamous and small cell carcinoma. No specific agent could be identified as particularly important for a specific histological type; it rather seemed that the effects of the substances considered were similar for lung cancers in general.

Occupational exposure and lung cancer risk in a coastal area of northeastern Italy

A case-control study of lung cancer and occupational exposure was conducted in a coastal area of Northeastern Italy where metallurgical and mechanical industries, docks and shipyards are located. Cases comprised 756 men who died of primary lung cancer in a 5-year period. Controls comprised 756 male subjects dying from other causes during the same period. Occupational exposures to lung carcinogens were assessed according to a job title-based approach, using two separate lists of industries/occupations recognized as being causally associated (list A) or suspected of being causally associated (list B) with lung cancer in humans. Exposure to asbestos was classified as absent, possible, or definite. After adjustment for cigarette smoking and place of residence, a significant association was found between lung cancer and occupations in both list A [relative risk (RR) = 2.25, 95% confidence interval (CI) = 1.68-3.03] and list B (RR = 1.33, 95% CI = 1.03-1.71). A significant excess risk was found for workers with definite exposure to asbestos as compared to those with no exposure to lung carcinogens (RR = 1.98, 95% CI = 1.42-2.75). Among occupations with recognized exposure to lung carcinogens other than asbestos, a significant excess risk for lung cancer was observed in iron and metalware workers. In occupational groups with definite exposure to asbestos, elevated risk estimates were found for shipyard workers, dockworkers, carpenters, and electricians. The combined effect of smoking and asbestos was found to be compatible with that expected under a multiplicative model. The overall population-attributable risk (ARp) for cigarette smoking was found to be 87.5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Histological type of lung carcinoma in asbestos cement workers and matched controls

Histological types of lung carcinoma were examined in a case series of workers exposed to asbestos cement dust (n = 29) and matched controls (n = 87). The proportion of adenocarcinomas was 31% among the exposed subjects and 15% among the controls (mid-p = 0.05). Among workers with high exposure the proportion of adenocarcinoma was even higher (45%, 5/11; mid-p = 0.03). The proportion of peripheral tumours tended to be higher among exposed cases than controls (24 v 12%, mid-p = 0.12). Lobe of origin did not differ, however, between exposed cases and controls. Thus the study indicates an association between the degree of exposure to asbestos and adenocarcinoma of the lung, and a peripheral rather than central localisation of the tumours, but with virtually the same distribution of lobe of origin as in the general population.

Cancer due to asbestos exposure

To determine the relationship between malignancies and asbestos exposure, the number of asbestos bodies in wet lung tissue was counted by light microscopy according to the modified method of Smith and Naylor, and occupational histories were examined. The results revealed that 17 (89 percent) of 19 malignant mesotheliomas, 39 (38 percent) of 104 lung cancers, 23 (37 percent) of 62 gastric cancers, and 13 (28 percent) of 45 colon cancers were shown to be cases with asbestos exposure. These values were significantly higher than those of noncancerous cases (200 cases). It is of interest that five out of ten cases of leukemia were related to asbestos exposure. Nearly all multiple cancers including lung and gastric cancer in this study were also cases with asbestos exposure. Additional research should be conducted on the carcinogenicity of asbestos for multiple cancers.

Smoking and peripheral type of cancer are related to high levels of pulmonary cytochrome P450IA in lung cancer patients

A specific member of the cytochrome P450 superfamily of enzymes, designated P450IA (including 2 isozymes, P450IA1 and P450IA2), which is involved in the metabolic activation of polycyclic aromatic hydrocarbons and aromatic amines, was studied in lung tissue from 25 lung cancer patients by immunohistochemistry. The pulmonary activity of a P450IA1-dependent enzyme, aryl hydrocarbon hydroxylase (AHH), from the same patients was also measured. Cytochrome P450IA was localized principally in the peripheral airways in alveolar epithelium of types I and II and in ciliated columnar and cuboidal bronchiolar epithelium. The amount of P450IA in the bronchial wall was minimal and was localized mainly in the capillary endothelium and the epithelium of the bronchial glands. Smoking was the most important factor related to the presence of P450IA and the AHH activity in lung tissue. None of the 10 ex-smokers, but all except I of the current smokers had detectable level of P450IA. The localization of the cancer was also correlated with the presence of cytochrome P450IA. Peripheral lung tissue stained positively in all patients with a peripheral adenocarcinoma who currently smoked (8/8) but in less than half of those with a bronchial cancer who were smokers (3/7). Our data suggest that the smokers who have an inducible cytochrome P450IA are especially at increased risk of developing lung cancer of the peripheral adenocarcinomatous type.

Cancer incidence among foundry workers in Denmark

Cancer incidence was studied among 6,144 male foundry workers who were invited to participate in either of two Danish national silicosis surveys conducted during 1967-1969 and 1972-1974. Cancer incidence was followed through to the end of 1985 by computerized linkage to the Danish Cancer Registry, and Standardized Morbidity Ratios (SMRs) were calculated based on incidence rates for the Danish population. For the entire cohort, significantly elevated SMRs were seen for all cancers (SMR, 1.09; 95% CI, 1.01-1.18) and lung cancer (SMR, 1.30; 95% CI, 1.12-1.51), and SMRs were at the borderline of statistical significance for bladder cancer (SMR, 1.24; 95% CI, 0.97-1.59). Excess lung and bladder cancer risk were confined to workers who had worked in foundries for at least 20 y. There was a positive correlation between silicosis prevalence in employees at the foundries at the time of the x-ray examinations and lung cancer incidence during the follow-up period. Squamous cell carcinomas, anaplastic carcinomas, and other lung cancers accounted for the excess lung cancer risk, whereas there was not excess risk among the foundry workers for adenocarcinomas of the lung.

Atopy and primary lung cancer. Histology and sex distribution

Atopy, defined as the ability to develop IgE antibodies to commonly encountered allergens under conditions of normal exposure, has an inherited component with pleiotropic effects. An inverse relationship between the occurrence of atopy, allergy-related diseases, and cancers at specific sites has been reported. The familial association of primary lung cancer is most evident among women, nonsmokers, and those with adenocarcinomas. In order to determine whether the relationship between a lower prevalence of atopy among patients with lung cancer compared to control subjects was consistent between histologic cell types, we used seven common allergens to allergy prick skin test 209 community control subjects (46 women), 109 cases with primary squamous cell carcinoma of the lung (25 women), and 67 patients with primary adenocarcinomas of the lung (23 women). We have confirmed earlier reports of an inverse relationship between atopy and lung cancer risk. In analyses focusing on sex and histologic cell type, we found that women with adenocarcinomas were an exception and were as likely to be atopic as control subjects. The evidence does not support a protective role for atopy among these women.

Proportion of lung and bladder cancers in males resulting from occupation: a systematic approach

Studies conducted in several countries that investigated the relationship of occupation and cancer in men were reviewed and compared. Estimates of the proportion of cancers due to occupational exposure that occurred in the general population were analyzed, and sources of variation were explored. A systematic and standardized evaluation of studies on lung and bladder cancer were undertaken, and only investigations that allowed for confounding from tobacco smoking were included. The proportion of lung cancers attributable to occupation ranged between 1 and 5% (when considering only exposure to asbestos) and 40% (in a study with a high proportion of subjects exposed to ionizing radiation); for bladder cancer, estimates were between 0 and 3% in a few studies and between 16 and 24% in several investigations. No similar attempt of systematic comparison was possible for other cancers.

Determinants of cell type in patients with cancer of the lungs

In order to evaluate the determinants of cell type in patients with primary lung cancer, we compared smoking characteristics in 1,939 patients (1,474 men and 465 women). Patients with squamous cell carcinomas, adenocarcinomas, or small-cell carcinomas were eligible. This study did not consider smoking as a risk factor for lung cancer, as all subjects had a confirmed diagnosis. We were interested in smoking history and the pattern of smoking among those whose risk was 100 percent. Among these patients, we confirmed that a larger subset of nonsmoking individuals developed adenocarcinomas than squamous cell or small-cell carcinomas; however, the duration and intensity of cigarette smoking, as measured by pack-years, were not determinants of tumor cell type in male patients. Small-cell carcinomas in women were more strongly associated with cigarette smoking than either squamous cell carcinomas or adenocarcinomas. More than 3,500 different substances have been measured in tobacco smoke, including tumor initiators, promoters, and those involved in tumor progression. These data confirm the hypothesis that factors other than cigarette smoking are more likely to be involved in the initiation of adenocarcinomas than other cell types. Endogenous and exogenous factors related to gender may be more important than the duration or intensity of cigarette smoking.

Transformed human bronchial epithelial cells (BEAS-2B) alter the growth and morphology of normal human bronchial epithelial cells in vitro

Normal human bronchial epithelial cells (BE) and adenovirus-12 SV40 hybrid virus transformed, non-tumorigenic human bronchial epithelial cells (BEAS-2B) were cultured for 7 days in a serum-free hormone supplemented medium. BE cells after 3 days in culture were exposed to conditioned medium (CMt) from confluent BEAS-2B cells. By day 7, CMt-treated BE cells exhibited a lower colony forming efficiency (CFE), fewer cells per colony, and a reduced mitotic index (MI) and BrdU (bromodeoxyuridine) labeling index. CMt also enhanced the expression of a terminally differentiated squamous phenotype in BE cells. Cell free lysates from BEAS-2B cells (CFLt) had effects similar to CMt on the MI and morphology of BE cells. In contrast, CMt and CFLt did not inhibit the growth, or alter the morphology of BEAS-2B cells. Conditioned medium from BE cells (CMn) did not reduce the growth of BEAS-2B cells, and had little effect on the morphology of BE cells. In co-cultures, BE cells in direct contact with BEAS-2B cells had a lower MI (0.4-0.7 vs. 1.6%) compared with colonies of BE cells in these cocultures. The concentration of transforming growth factor beta (TGF-beta) in conditioned media from BEAS-2B cells (CMt) was increased 10-fold over that in CMn. TGF-beta is known to induce terminal differentiation in epithelial cells. These results suggest that the selective growth advantage of transformed cells over normal cells during human bronchial carcinogenesis may be related to the release of autocrine/paracrine factors (e.g., TGF-beta) from transformed cells, which down-regulates and terminally differentiates the normal cells.

Relationship between occupation and lung cancer as analyzed by age and histologic type

The information on occupations obtained in Finland's 1970 census was linked with the files of the Finnish Cancer Registry from 1971 through 1980 in order to establish the occupational group-specific relative risks (RR) of lung cancer. The distribution of lung cancers into histologic types varied with the age of the patients at the time of diagnosis. When 38 high-risk occupational groups were combined, the age-specific distribution of lung cancer into histologic types did not differ significantly from the corresponding distribution for other economically active men. Of individual occupational groups, young farmers had a higher RR of small cell carcinoma than older farmers or other economically active young men. Besides their high overall lung cancer risk, miners and quarriers had a very high risk of small cell carcinoma as compared with other economically active men. Servicemen and repairmen in the metal industry had a high risk of epidermoid carcinoma. Welders had a high risk of epidermoid carcinoma, but their risk of small cell carcinoma was lower than expected. There were no other excess risks of any histologic type of lung cancer attributable to occupational factors.

Study of asbestos bodies in Japanese urban patients

To study whether low-level exposure to asbestos contributes to lung cancer risk, the asbestos body (AB) content in lung tissue was measured in 476 patients with lung cancer and 369 patients with other diseases, all from a Japanese industrialized city. Eleven patients with histologically confirmed asbestosis were included. The findings were stratified into four groups. A significant number of patients with lung cancer were seen in the groups with high counts, as compared to controls. There was no significant difference in histologic type and site of lung cancer among four groups. The patients with lung cancer in high count groups were significantly younger than those with lower counts. A significant number of smokers were seen in the groups with high AB counts among patients with lung cancer as compared to controls, even if the patients with asbestosis were excluded. These findings suggest that there may be a positive interaction of smoking and exposure to asbestos relative to the incidence of lung cancer even at a low exposure level.

Characteristics of patients with primary lung cancer diagnosed at age of 50 years or younger

We examined the extrinsic and intrinsic characteristics of patients with primary lung cancer diagnosed at early ages and compared them with those of older patients. Significant differences in gender distribution and histologic cell type were present. Cigarette smoking was an important etiologic factor in both groups.

Study of lung cancer histologic types, occupation, and smoking in Missouri

A case-control study of lung cancer was conducted to evaluate the relationship between lung cancer histologic types and occupation, adjusted for smoking. A total of 4,431 white male cases and 11,326 cancer controls, diagnosed between 1980 and 1985, were identified through the Missouri Cancer Registry. For all histologic types combined, excess risk was observed among many a priori suspected high-risk occupations. Lung cancer was elevated among men employed as insulators (odds ratio [OR] = 6.0; 95% confidence interval [CI] = 0.7, 137.8), carpenters (OR = 1.3; 95% CI = 1.0, 1.7), painters, plasterers, and wallpaper hangers (OR = 2.0; 95% CI = 1.2,3.3), structural metal workers (OR = 1.9; 95% CI = 0.6,6.0), mechanics and repairers (OR = 1.3; 95% CI = 1.0,1.7), motor vehicle drivers (OR = 1.5; 95% CI = 1.2,1.8), police and firefighters (OR = 1.6; 95% CI = 1.1,2.3), and food service personnel (OR = 1.8; 95% CI = 1.0,3.5). A deficit of lung cancer was observed among farmers (OR = 0.9; 95% CI = 0.7,1.0). Adenocarcinoma of the lung was elevated among carpenters (OR = 1.6; 95% CI = 1.0,2.5) and cabinet and furniture makers (OR = 2.0; 95% CI = 0.4,8.1), which is interesting because of the previous reports of excess adenocarcinoma of the nasal cavity associated with wood dust exposure. Adenocarcinomas were also elevated among plumbers (OR = 2.0; 95% CI = 1.0,3.8) and printers (OR = 1.8; 95% CI = 0.7,4.2). Electricians were at slightly increased risk for adenocarcinoma (OR = 1.5; 95% CI = 0.7,2.8) and "other" or mixed cell types of lung cancer (OR = 1.5; 95% CI = 0.8,2.9) but at decreased risk for small cell (OR = 0.8; 95% CI = 0.3,2.0) and squamous cell (OR = 0.8; 95% CI = 0.4,1.6) tumors. Among welders, adenocarcinoma (OR = 1.7; 95% CI = 0.7,3.8) and squamous cell (OR = 1.7; 95% CI = 0.9,3.3) cancers were elevated, but small cell and "other" lung cancers were not. Despite the limitations of the Cancer Registry data, some interesting associations were observed that merit further study, particularly the association between lung adenocarcinoma and occupational exposure to wood and wood dust.

Occupation and lung cancer in Shanghai: a case-control study

Occupation was evaluated as a potential risk factor for lung cancer as part of a large population based case-control study conducted in the ten urban districts of Shanghai. A total of 733 newly diagnosed cases of male lung cancer and 760 controls selected from the general population was interviewed to obtain lifetime occupational histories and information on smoking and other factors. Of the approximately 25 major industrial titles examined, significantly raised risks, adjusted for smoking, were found for employment in agricultural production (odds ratio (OR) = 1.6, 95% confidence interval (CI) = 1.0-2.6). A concomitant increase was detected for farmers (OR = 1.6, 95% CI = 1.0-2.5) when 35 major occupational titles were examined. There was a 70% excess among workers in the chemical industry (OR = 1.7, 95% CI = 0.9-3.1) and a significant decrease among textile industry workers (OR = 0.7, 95% CI = 0.5-1.0). Raised risks of 30% to 80% were associated with reported job exposures to wood and coal dusts, smoke from burning fuels, and chemical fumes. Employment categories were also examined for 672 cases and 735 controls among women, but small numbers in many of the industrial and occupational categories precluded detailed analyses. The largest excess risk among women (OR = 5.1, 95% CI 1.3-23.5) was among glass products workers. Although cigarette smoking was the dominant cause of lung cancer among men and a significant risk factor among women in Shanghai, these findings suggest the importance of certain workplace exposures and offer leads to occupational carcinogens.

Cancer in the respiratory organs of Swedish farmers

In a cohort of 254,417 male Swedish farmers (4,330,717 person-years) the incidence of cancer of the respiratory organs was compared to a reference cohort of 1,725,845 men (30,131,664 person-years) employed in other economic activities than agriculture or forestry. In the study cohort 1450 cases of cancer in the respiratory organs were found in 1961 to 1979 resulting in an estimated relative risk (RR) of 0.38 (95% confidence interval [CI]: 0.36-0.40). For cancer of trachea, bronchus and lung, the decreased risk was equal for adenocarcinoma and squamous cell carcinoma. No time related trend in RR for any of the histologic subtypes could be seen. However, for squamous cell carcinoma in nose and nasal sinuses RR has increased from 0.42 (95% CI: 0.20-0.80) in 1961 to 1966 to 2.06 (95% CI: 1.22-3.50) in 1974 to 1979.

Histologic types of lung cancers among male Japanese copper smelter workers

This study was done to investigate which histologic type of lung cancer is prevalent among male Japanese copper smelter workers. A panel of eight pathologists was asked to diagnose uniformly prepared materials for 19 occupational series, 87 nonoccupational bronchogenic carcinomas, and 14 benign lesions. The consensus diagnosis was used as reference. The reference diagnoses and the originals without materials employed for verification were designated as finals. Squamous cell carcinoma was the most frequent cell type in the occupational group, which comprised 21 (75.0%) of 28 histologically proven cases. There were three (10.7%) small cell carcinomas, one (3.6%) large cell carcinoma, and three (10.7%) adenocarcinomas. The proportion of Kreyberg group I in the occupational cases was significantly larger than that of lung cancers in the population-based cancer registries in Japan. These findings are compatible with Kreyberg's hypothesis. Above all, squamous and small cell carcinomas were prominent and appeared to be environmentally related bronchogenic carcinomas.

Female-male differences in patients with primary lung cancer

This report is based on responses to a mailed questionnaire from 927 patients with lung cancer (730 men, 197 women), or their next of kin, and information obtained from the Saskatchewan Cancer Foundation Tumour Registry. Women were diagnosed at an earlier mean age than males (means +/- SE, 63.5 +/- 0.85 years versus 67.6 +/- 0.37 years, P less than 0.001), a finding which was consistent for each major histologic type. Women were more frequently diagnosed before age 60 years (42.0%) than were men (25.6%) (P less than 0.001). Female patients were significantly more likely to be lifetime nonsmokers of cigarettes than male patients (23% versus 3.7%, P less than 0.001). Among current smokers, women started smoking at an older age (19.3 +/- 0.69 versus 16.5 +/- 0.21 years, P less than 0.001), smoked for fewer years (41.0 +/- 1.2 years versus 47.4 +/- 0.57 years, P less than 0.001) and smoked slightly fewer cigarettes per day than male patients (23.6 +/- 1.0 versus 26.7 +/- 0.63, P less than 0.05). Similar results were found for the duration of the smoking habit and number of cigarettes smoked among exsmokers. When current smokers and exsmokers were combined, the distribution of pack years by gender was significantly different. A higher percentage than expected of women as compared to men, are clustered in the lower pack-year categories (P less than 0.0003). No occupational exposure or familial factors which might act in synergism with cigarette smoking were identified. Thus, women developed primary lung cancer at an earlier age while smoking for fewer years than men.