Sex differences in lung-cancer risk associated with cigarette smoking

Specific Features of Non-small Cell Lung Cancer in Women: A Retrospective Study of 1738 Cases Diagnosed in Bas-Rhin between 1982 and 1997

INTRODUCTION

The literature suggests that lung cancer may represent a different disease in women compared with men and that gender specificities have been reported mostly in clinical trials patients.

METHODS

We conducted a retrospective, population-based study of a sample of 1738 patients diagnosed with a non-small cell lung cancer (NSCLC) in the department of Bas-Rhin (northeastern France) between 1982 and 1997. Our study aimed to describe symptoms at presentation, stage, histological distribution, treatment modalities, and survival, according to sex.

RESULTS

Tobacco exposure differed significantly according to sex: 28.9% of women were nonsmokers versus 1.4% of the men. More NSCLC were metastatic at diagnosis in women than in men (41.1% versus 29.9%). Adenocarcinoma predominated in women (54.4%), whereas squamous cell carcinoma predominated in men (65.9%). Invasive procedures, such as transthoracic needle biopsy, contributed more frequently to histological diagnosis in women. Men and women underwent the same procedures for disease staging, excepted for the abdominal computed tomography scan, which was performed more frequently in women. Treatment also differed: in resectable disease, fewer pneumonectomies were performed in women; in locally advanced disease, the mean doses of thoracic irradiation were significantly lower in women (48.0 grays versus 55.5 grays); in metastatic-stage disease, fewer women received platin-based chemotherapy, but this difference was not significant. Sex was not a significant prognostic factor in our study, contrary to most North American studies, where women seem to have had better survival rates.

CONCLUSIONS

This study emphasizes gender differences in smoking exposure, presentation (stage, histological subtype), and diagnostic and therapeutic management of NSCLC.

The growing burden of chronic obstructive pulmonary disease and lung cancer in women: examining sex differences in cigarette smoke metabolism

Smoking-related lung diseases such as chronic obstructive pulmonary disease (COPD) and lung cancer are growing epidemics in women in the United States and elsewhere. Although some of this disturbing trend in women can be attributed to changing smoking habits, there is emerging evidence that women may be biologically more susceptible to the harmful effects of cigarette smoke than are men. Estrogen and related compounds may up-regulate the expression of cytochrome P450 (CYP) enzymes in lungs and liver, which are involved in the metabolism of various constituents of cigarette smoke. Although metabolism of foreign substances is usually beneficial in eliminating potential toxins from the body, in some instances the metabolic process can transform harmless substances into toxic chemicals through a process called metabolic bioactivation. One important xenobiotic substrate for CYP enzymes in cigarette smoke is polycyclic aromatic hydrocarbon, which in its native form is relatively harmless in small doses but upon bioactivation by CYP enzymes, can become very toxic substances for the lungs. In this article, we explore CYP and other related pathways as potential mechanisms and targets of future research and novel discoveries to curb the growing epidemic of COPD and lung cancer in women.

A possible role for dihydrodiol dehydrogenase in the formation of benzo[a]pyrene-DNA adducts in lung cancer cells and tumor tissues

Epidemiological studies indicate that there is a gender difference in the susceptibility to tobacco and environmental carcinogens, and this gender difference is suspected to result in a higher risk for lung cancer among women. However, the molecular mechanisms underlying this sexual dimorphism remain unclear. In the present study, we have evaluated the roles of CYP1A1 and dihydrodiol dehydrogenase (DDH) in the formation of benzo[a]pyrene (BaP) DNA adducts in various lung cancer cell lines. Among six lung cancer cell lines tested, higher adduct levels were observed in CL-3 and CL1-1 cells, which had relatively high expression of both CYP1A1 and DDH isoform 1 (DHH1). To determine whether a reduction in DDH expression changed the adduct levels, an siRNA was used to knock down DDH1 expression in CL-3 cells. The BaP adduct levels in siDDH-CL-3 cells increased 1.4-2.2-fold relative to that of the parental CL-3 cells. We also examined BaP-like DNA adducts, and CYP1A1 and DDH1 expression by immunohistochemistry in 120 lung tumors. Detection of DNA adducts correlated with CYP1A1-positive tumors (P = 0.023), but not with DDH1-positive tumors. In addition, 28 of 33 tumors (85%) that were CYP1A1-positive and DDH1-negative contained detectable levels of DNA adducts, a proportion that was higher than for tumors from the other three categories of CYP1A1 and DDH1 expression (P = 0.012). Finally, a greater proportion of adduct-positive tumors from females were CYP1A1-positive/DDH1-negative (45.3%) than were tumors from males (27.3%). These results suggest that the reduction of DDH expression in lung tumors may contribute to an increase in DNA adduct levels, which may be partly responsible for the higher susceptibility of female lung cancer patients to DNA damage.

Lung cancer in women: exploring sex differences in susceptibility, biology, and therapeutic response

Src tyrosine kinases regulate a large number of important mechanisms in normal and cancerous cells, are overexpressed in a broad range of tumors including lung cancer, and thus represent a potential target for cancer therapy. Preclinical experiments indicate that small-molecule inhibitors of Src block tumor growth, metastasis, and angiogenesis. Phase I data from healthy volunteers also suggest that inhibitors of Src prevent bone resorption. Several phase II trials with small-molecule inhibitors of Src are under way or have been initiated in lung cancer and in other malignancies, as discussed herein.

Changing epidemiology of small-cell lung cancer in the United States over the last 30 years: analysis of the surveillance, epidemiologic, and end results database

PURPOSE

Small-cell lung cancer (SCLC) is a histologic subtype of lung cancer with a distinct biology and clinical course. It has been observed that the incidence of SCLC has been decreasing over the last several years.

METHODS

We used the Surveillance, Epidemiologic, and End Results (SEER) database to determine the incidence of SCLC over the last 30 years. In addition, we sought to determine sex- and stage-based differences in the incidence and survival of SCLC among a proportion of reported cases of lung cancer over the last 30 years (1973 to 2002). Joinpoint analyses were applied to test the trends in annual percentage change for statistical significance.

RESULTS

The proportion of SCLC (among all lung cancer histologic types) decreased from 17.26% in 1986 to 12.95% in 2002. Of all patients with SCLC, the proportion of women with SCLC increased from 28% in 1973% to 50% in 2002. A modest but statistically significant improvement in 2- and 5-year survival was noted among both limited-stage SCLC and extensive-stage SCLC cohorts during the study period.

CONCLUSION

Our analysis indicates that the incidence of SCLC is decreasing in the United States, and only modest improvements have been seen in survival over the last 30 years. Possible explanations for the decreasing incidence include the decrease in the percentage of smokers and the change to low-tar filter cigarettes. Despite trends toward modest improvement in survival, the outcome remains very poor.

Use of exogenous hormones by women and lung cancer: evidence from the Royal College of General Practitioners' Oral Contraception Study

OBJECTIVE

The objective of this study was to assess the risk of lung cancer among women who have used oral contraception or hormone replacement therapy (HRT), especially those exposed to both classes of exogenous hormones.

DESIGN

This study is a nested case-control one using prospectively collected data from the Royal College of General Practitioners' Oral Contraception Study (OCS). The 162 case patients were women with a diagnosis of lung cancer recorded on the OCS database by August 2004. Each case patient was matched with 3 control subjects who were free of the disease at the time of the case patient's diagnosis, of similar age and with similar length of follow-up in the OCS.

RESULTS

Compared with never use, current use of oral contraception was associated with a statistically nonsignificant reduced risk of lung cancer, with an adjusted odds ratio (OR) of 0.47 and a 95% confidence interval (CI) of 0.08-2.95 (OR=0.86 and 95% CI=0.50-1.48 for former use; OR=0.84 and 95% CI=0.49-1.43 for ever use). Similar comparisons for HRT were current use (OR=1.21, 95% CI=0.23-6.37), former use (OR=0.62, 95% CI=0.23-1.68) and ever use (OR=0.71, 95% CI=0.28-1.78). The OR among women who had used both classes of hormones was 0.53 (95% CI=0.16-1.72), as compared with those who had used neither.

CONCLUSIONS

Our results are compatible with findings from other studies that suggest that oral contraceptives may reduce the risk of lung cancer. Evidence for a beneficial effect of HRT is less convincing. Further study is needed to determine how long any benefit lasts and whether it is stronger in women exposed to both classes of exogenous hormones. The small number of events occurring in this very large cohort, however, shows that any public health benefit is likely to be marginal.

Lung cancer in women

Lung cancer is the leading cause of cancer death in the United States and is responsible for 20,000 more deaths yearly in US women than breast cancer. Cigarette smoking is the major cause of lung cancer, and unfortunately, approximately 22 million US women smoke. Mounting evidence suggests that there are significant differences in lung cancer between the sexes. There is a difference in the histologic distribution of lung cancer, with glandular differentiation being more common in women. Genetic variation may account for differences in susceptibility, and hormonal and biologic factors may play a role in carcinogenesis. Lung cancer patients have few therapeutic options. A more thorough understanding of the heterogeneity of lung cancer across populations may lead to innovations in treatment and prevention strategies.

Lung cancer in women

Lung cancer is one of the most important avoidable causes of death around the world, it is the most widespread carcinoma with a very poor prognosis, and is the leading cause of cancer death in both developed and developing countries. At present more men than women die each year from lung cancer, but in recent years a rapid increase in lung cancer mortality has been observed among women in developed countries, contrasting with a levelling off or decrease among men. The rising trend in female lung cancer mortality has been observed to parallel with the past and current prevalence of cigarette smoking among women in the United States and elsewhere. An important role of other factors acting either as independent risk factors or interacting with the effect of smoking has been suggested by some studies among women, among them genetic, biologic and hormonal factors, and probably some factors related to the environment and lifestyle. There is a controversy concerning the claim that women have a different susceptibility to tobacco carcinogens, which might or might not be greater than men do. Since tobacco is far and away the strongest epidemiological risk factor for the development of lung cancer, comprehensive smoking control efforts are the priority in the prevention of lung cancer among women.

Complex segregation analysis reveals a multigene model for lung cancer

Lung cancer risk is largely attributed to tobacco exposure, but genetic predisposition also plays an etiologic role. Several studies have investigated the involvement of genetic predisposition in lung cancer aggregation in affected families, although with inconsistent results. Some studies have provided evidence for Mendelian inheritance, whereas others have suggested that environmental models are most appropriate for lung cancer aggregation in families. To examine the genetic basis of lung cancer, we performed segregation analysis on 14,378 individuals from 1,561 lung cancer case families, allowing for the effects of smoking, sex, and age. Both a Mendelian decreasing model and a Mendelian codominant model were found to be the best fitting models for susceptibility. However, when we modeled age-of-onset, all Mendelian models and the environmental model were rejected suggesting that multiple genetic factors (possibly multiple genetic loci and interactions) contribute to the age-of-onset of lung cancer. The results provide evidence that multiple genetic factors contribute to lung cancer and may act as a guide in further studies to localize susceptibility genes in lung cancer.

Women and tobacco dependence

Millions of American girls and women have been drawn to smoking by an industry that has been clearly and systematically targeting women of all ages and life circumstances. Tobacco marketing strategies skillfully link cigarette use to typical female values. Biologically speaking, women are especially vulnerable to the legion of health problems of tobacco use. Smoking is a critical hazard for women in their reproductive years, particularly when they are pregnant.

Gender and lung cancer

Although lung cancer is the leading cause of cancer death among men and women in the United States, female smokers appear to be at increased risk. After controlling for the number of cigarettes smoked, female sex imparts a significant, independent risk for most histologic types of lung cancer. Cigarette smoking, genetics, and endocrine factors may interact to contribute to the disparity in lung cancer risk between the sexes. Estrogens have direct and indirect actions in the lung, and estrogen has been implicated in lung carcinogenesis in female smokers. This review of the literature will focus on endocrine factors and tobacco carcinogens as risk factors for lung cancer in women.

Improved survival in never-smokers vs current smokers with primary adenocarcinoma of the lung

STUDY OBJECTIVES

Adenocarcinoma of the lung is now the most common histologic subtype of lung cancer in the United States. To determine if there are survival differences in never-smokers and current smokers with adenocarcinoma, we conducted an analysis of lung adenocarcinomas seen at the H. Lee Moffitt Cancer Center, and looked for demographic and survival differences in the two groups.

DESIGN

Data were gathered through the tumor registry at the H. Lee Moffitt Cancer Center and confirmed by chart review. A total of 132 documented never-smokers and 522 current smokers with lung adenocarcinoma were included. Detailed demographic survival information were gathered and tabulated. Former smokers were not included in the study. Multivariate analyses were performed using the Cox regression method to identify variables with independent prognostic significance. Life table actuarial analyses were performed to determine survival. Differences between survival curves were estimated using the log-rank test.

RESULTS

The mean age at diagnosis for never-smokers was higher as compared to current smokers: 63.5 years vs 59.4 years (p = 0.0005). In addition, there was an increased percentage of female subjects in the never-smoker category: 78% vs 54% (p < 0.0001). There was a statistically significant difference in survival between current smokers and never-smokers (p = 0.004). The Kaplan-Meier estimates at 5 years were 16% for current smokers and 23% for never-smokers. On multivariate analyses, smoking was identified as an independent negative prognostic factor.

CONCLUSION

Our data show that never-smokers with adenocarcinoma are predominantly female, present at a higher mean age, and have improved survival when compared to current smokers. By multivariate analyses, the never-smoking status was found to be an independent predictor of improved survival. The survival difference may be partly influenced by less comorbidity among never-smokers. Nevertheless, owing to differences in the mechanism of carcinogenesis (in smokers vs nonsmokers), demographic factors, tumor behavior and survival, adenocarcinomas occurring in never-smokers may display a distinct natural history and may warrant further investigation as a separate entity with epidemiologic studies and clinical trials designed specifically for this category of non-small cell lung cancer.

Gender and lung cancer

Accumulating data suggest that the risks for development of lung cancer are different in women compared with men. An increased susceptibility in women to the adverse effects of tobacco may be due to higher levels of DNA adducts, decreased DNA repair capacity, increased frequency of mutations in tumor suppressor genes, and hormonal differences. There are many sex and gender differences in lung cancer presentation, including a greater proportion of adenocarcinoma among women, a greater representation of women in cohorts of younger patients who have lung cancer, and women who do not smoke are more likely to be diagnosed with lung cancer than men. When guidelines for screening, preventive therapies, and treatment options for lung cancer are outlined these differences should be considered.

Clinical course of lung cancer in patients with chronic kidney disease

Co-morbidity has a major impact on survival in early and late-stage lung carcinoma. Patients maintained on dialysis are potentially at increased risk of cancer. However, since very few studies have examined the clinical course of lung cancer in patients with chronic kidney disease (CKD), we felt it was important to study the course of non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) in this patient population. We performed a retrospective chart review of patients diagnosed with lung cancer and co-existent CKD. 107 patients (101 males and six females), with a mean age at diagnosis of 69 years (range: 39-86 years) were included in our study. Of these, 17 (15.9%) patients had SCLC while 87 (81.3%) had NSCLC. Dyspnea, weight loss, and chest pain were the most common symptoms at presentation in our patient population occurring in 25, 20, and 15% of patients, respectively. The median survival of all the patients in the study was 10 months (range: 0-116 months). Patients with SCLC had a median survival of 7 months. Patients with NSCLC had a median survival of 10 months. We found that the clinical course and survival in patients with lung cancer and CKD appear to be comparable to that of patients with lung cancer, but without kidney dysfunction. Hence though treatment of lung cancer does need to be individualized in the setting of CKD, it should not dissuade the clinician from treating the malignancy.

Epidemiology of substance use disorders in women

Significant gender differences exist in the prevalence of substance use disorders in the United States. There is a trend among boys and girls aged 12 to 17 years toward comparable rates of use and initiation for alcohol, cocaine, heroin, and tobacco. If this trend continues, over time there may be a narrowing of the male-to-female prevalence ratios of substance abuse in the older age groups. This possibility is particularly disturbing because women have a heightened vulnerability to medical, physical, mental, and social consequences of substance use. Women also carry additional unique risks during pregnancy because of the effect on neonates. In addition, they have certain gender-specific cancer risks. Given this and the declining age of initiation of substance use in women, prevention and treatment efforts especially geared toward women (eg, education of all medical and paramedical staff, screening in primary care clinics, detection of drug use early in pregnancy or before conception, brief interventions and treatment programs that integrate women's needs) are exceedingly important to stop and ultimately reverse this growing trend.

Women and small cell lung cancer: social characteristics, medical history, management and survival

The literature make it clear that lung cancer in women differs from that in men in several specific aspects. We conducted a retrospective study of the 967 consecutive recorded patients (696 men and 91 women after exclusions) diagnosed with small cell lung cancers (SCLC) between 1981 and 1994 in the Bas-Rhin population-based cancer registry to determine if such particularities could be observed in SCLC. Data included demographic and social characteristics, medical and smoking history, management (diagnosis and treatment), hospitalisation and survival. The end point for survival was 31 December 1998. Women were more frequently single, divorced, or widowed (P=0.007) and lived more often in urban areas (places with more than 10,000 inhabitants) (P=0.017). They differed significantly from men in their tobacco exposure (P=0.0001) and non-smoking rates (P=0.0003) but not in clinical presentation, except for more frequently elevated LDH levels (P=0.02). Bone marrow biopsies were more often performed in men (P=0.004), but management was otherwise comparable. The mean number of hospitalisations (for any reason) was comparable in both sexes but women tended to remain hospitalised longer (P=0.057). Overall survival did not differ, but women older than 70 years died sooner than their male counterparts (P=0.026). Our study confirms that some of gender differences reported in the lung cancer literature exist in SCLC. Sex-related differences in LDH levels have not previously been reported, to our knowledge. North American and European data concerning survival among women and men are discordant. Whether these gender differences are related to a real difference between the sexes or simply to differential exposure to carcinogens remains to be determined.

Variations in lung cancer risk among smokers

BACKGROUND

Although there is no proven benefit associated with screening for lung cancer, screening programs are attracting many individuals who perceive themselves to be at high risk due to smoking. We sought to determine whether the risk of lung cancer varies predictably among smokers.

METHODS

We used data on 18 172 subjects enrolled in the Carotene and Retinol Efficacy Trial (CARET)-a large, randomized trial of lung cancer prevention-to derive a lung cancer risk prediction model. Model inputs included the subject's age, sex, asbestos exposure history, and smoking history. We assessed the model's calibration by comparing predicted and observed rates of lung cancer across risk deciles and validated it by assessing the extent to which a model estimated on data from five CARET study sites could predict events in the sixth study site. We then applied the model to evaluate the risk of lung cancer among smokers enrolled in a study of lung cancer screening with computed tomography (CT).

RESULTS

The model was internally valid and well calibrated. Ten-year lung cancer risk varied greatly among participants in the CT study, from 15% for a 68-year-old man who has smoked two packs per day for 50 years and continues to smoke, to 0.8% for a 51-year-old woman who smoked one pack per day for 28 years before quitting 9 years earlier. Even among the subset of CT study participants who would be eligible for a clinical trial of cancer prevention, risk varied greatly.

CONCLUSIONS

The risk of lung cancer varies widely among smokers. Accurate risk prediction may help individuals who are contemplating voluntary screening to balance the potential benefits and risks. Risk prediction may also be useful for researchers designing clinical trials of lung cancer prevention.

Missed non-small cell lung cancer: radiographic findings of potentially resectable lesions evident only in retrospect

PURPOSE

To assess for change in the 1990s in the failure of detection at chest radiography of potentially resectable non-small cell lung cancer (NSCLC) lesions compared with experience in the previous decade.

MATERIALS AND METHODS

From 1993 to 2001, an observational cohort was identified that consisted of 40 instances of NSCLC evident retrospectively at chest radiography but undetected by a radiologist at a time when the cancer was potentially resectable for cure. Sizes and locations of the tumors were assessed. Pearson chi(2) testing was performed to compare the sex distribution of lung cancer in the present series with population data for the sex distribution of lung cancer in the United States during the present study.

RESULTS

Twenty-five (62%) undetected NSCLCs were in men and 15 (38%) were in women, yielding a ratio not significantly different from that for the sex distribution of NSCLC according to national data (chi(2) = 0.22, P =.64). Median patient age was 62 years (range, 37-87 years). Median diameter of the missed cancers was 1.9 cm. Missed cancers were most commonly located in the upper lobes (right, 45%; left, 28%; total, 72%), especially in the apical and posterior segments/subsegments (60% of all the missed cancers). A clavicle obscured 22% of the missed cancers. Eighty-five percent of the missed cancers were in peripheral locations.

CONCLUSION

Potentially resectable NSCLC lesions missed at chest radiography were characterized by predominantly peripheral (85%) and upper lobe (72%) locations and by apical and posterior segmental/subsegmental locations in an upper lobe (60%). Distribution by sex of the missed cancers was comparable to national data for NSCLC. The missed cancers had a median diameter of 1.9 cm.

Tobacco use and cancer: an epidemiologic perspective for geneticists

Much of what is known about the deleterious effects of tobacco use on health was learned from epidemiologic studies over the last half century. These studies establish unequivocally that tobacco use, particularly manufactured cigarette smoking, causes most cancers of the lung, oropharynx, larynx, and esophagus in the USA, and approximately one-third of all cancers of the pancreas, kidney, urinary bladder and uterine cervix. More recent evidence also implicates smoking with cancers of the stomach, liver and colorectum. While over half of the estimated 440 000 smoking-attributable deaths that occur annually in the USA involve non-malignant cardiovascular and respiratory conditions, smoking-attributable cancers are more recognized and feared. Geneticists increasingly study tobacco use as a model for environmental carcinogenicity. Tobacco-exposed populations provide opportunities to characterize the somatic mutations that give rise to specific cancers and to identify the inherited genetic traits that confer susceptibility or resistance. Studies to identify the genetic determinants of addiction may be particularly important. Future research to identify other susceptibility factors, such as genes that modify carcinogen metabolism or DNA repair, will need to be substantially larger and to quantify lifetime tobacco exposure with more precision than have past studies in order to distinguish gradations in risk due to exposure from those caused by genetic susceptibility. This review considers: (a) the epidemiology of tobacco use; (b) cancers presently classified as smoking-attributable by the US Surgeon General; (c) the magnitude of the epidemic of cancers and other diseases caused by tobacco use; (d) selected issues in the epidemiology of lung cancer; and (e) the interface of genetics and epidemiology in understanding, preventing, and treating tobacco-attributable disease.

Epidemiology, etiology, and prevention of lung cancer

Over the past century, lung cancer has gone from an obscure disease to the leading cause of cancer death worldwide. Initially an epidemic disease among men in industrialized nations, lung cancer now has become the leading cancer killer in both sexes in the United States and an increasingly common disease of both sexes in developing countries. Lung cancer incidence largely mirrors smoking prevalence, with a latency period of several decades. Other important risk factors for the development of lung cancer include environmental exposure to tobacco smoke, radon, occupational carcinogens, and pre-existing nonmalignant lung disease. Studies in molecular biology have elucidated the role that genetic factors play in modifying an individual's risk for lung cancer. Although chemopreventive agents may be developed to prevent lung cancer, prevention of smoking initiation and promotion of smoking cessation are currently the best weapons to fight lung cancer. No other malignancy has been shown to have such a strong epidemiologic relation between a preventable behavior and incidence of disease. Despite this knowledge, more than 20% of all Americans smoke, and tobacco use is exploding in developing countries. Based on current and projected smoking patterns, it is anticipated that lung cancer will remain the leading cause of cancer death in the world for decades to come.

Lung cancer incidence in Australia: impact of filter-tip cigarettes with unchanged tar yields

Filter-tip cigarettes became popular in Australia in the late 1950s, but "tar" yields remained high for another decade. Because of this, the effect of filters independently of tar reductions can be estimated by comparing the age-adjusted incidence of lung cancer for relevant birth cohorts of Australians. Separate analyses by histologic type may throw some light on the specific effects of filters. Age-adjusted incidence of squamous cell carcinoma (SCC), small cell lung carcinoma (SCLC) and adenocarcinoma (AC) was estimated by Poisson regression for 5-year birth cohorts of Australians using lung cancer registration data for 1982-95. To take account of changes in smoking prevalence, ever-smoker less never-smoker differences in age-adjusted incidence were estimated. Comparisons were made for smokers born during 1930-34 and 1940-44. Smokers born in 1940-44 commenced smoking at the time of introduction of filter-tips. Age-adjusted incidence of SCC (-23%) and SCLC (-21%) but not AC (+7%) was lower for female smokers born during 1940-44. For male smokers, rates of SCC (-42%), SCLC (-43%) and AC (-24%) were each lower. The high rates overall of 1940s-born women were due to disproportionately higher incidence of AC, the type that comprised 42% of diagnoses with histologic confirmation. In Australia, the switch to filter-tip cigarettes prior to any reduction in tar yields was associated with reduced incidence of SCC and SCLC, and of AC for men only. Rates of AC were not reduced for women, indicating that other factors were important for this type of lung cancer.

Smoking cessation in women. Special considerations

Women may be at relatively greater risk of smoking-related diseases than men but tend to have less success than men in quitting smoking. The failure of most outcome studies to report results by gender and the lack of statistical power for detecting significant gender differences currently do not allow for many firm conclusions to be drawn about smoking cessation rates in women, but several trends warrant attention and further study. First, the difference in cessation rates for women versus men may be even greater in trials of nicotine replacement therapies (NRT). This suggests that women benefit less from NRT relative to men, although this difference may depend on the particular form of NRT (e.g. inhaler versus gum). On the other hand, some non-NRT medications may reverse the poorer outcome of women, producing quit rates in women comparable with those in men. Gender differences in outcome, as well as overall success rates, with NRT and some of the non-NRT medications appear to be enhanced when treatment includes substantial behavioural counselling. However, while several of the non-NRT medications may be particularly appropriate to consider for treating women trying to quit smoking, adverse effects may limit widespread use of some of these drugs, such as clonidine and naltrexone. Thus, even if the gender differences in outcome with NRT versus non-NRT drugs are confirmed in further research, such findings do not necessarily justify limiting NRT use in women, because such treatment is clearly effective and is likely to be safer and more readily available than non-NRT medications. Nevertheless, study of the mechanisms by which some non-NRT drugs are effective in women may aid our understanding of factors that are more influential in smoking behaviour in women than in men. Secondly, smoking cessation treatment for women must address several other issues that often emerge, and these are most likely to require behavioural counselling that is tailored to these problems. These issues include concern about bodyweight gain, restrictions on medication use in pregnant smokers, variability in mood and withdrawal as a function of menstrual cycle phase, harnessing social support to foster abstinence, and the possibility that smoking-associated environmental cues may be more influential in smoking behaviour in women than men. Greater attention to gender differences in clinical trial outcomes and to addressing concerns of women smokers may aid in the development of substantially improved smoking cessation interventions for women.

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.

Women and lung cancer: does oestrogen play a role?

Smoking-related disease remains a major public-health problem. Large numbers of women continue to smoke, and new smokers are almost as likely to be female as male. Lung cancer is still a largely incurable disease; annual lung-cancer mortality in women exceeds that of breast cancer, and lung cancer now accounts for 12% of all new female cancer cases. The results of several studies suggest that women are more susceptible than men to lung cancer and to conditions that predispose to this cancer, such as chronic obstructive pulmonary disease. There is still much controversy about whether there is an increased lung-cancer risk in women across all populations. Many epidemiological studies have been negative or equivocal when comparing male and female lung-cancer risk. This article is not intended to be a comprehensive review of all epidemiological studies, or of all possible lung-cancer risk factors. Lung-cancer incidence and risk in women are discussed, and evidence for possible mechanisms of increased female risk are presented, including the role of oestrogen in the development of lung cancer.

Gender- and smoking-related bladder cancer risk

BACKGROUND

There is growing evidence that, when smoking habits are comparable, women incur a higher risk of lung cancer than men. Because smokers are also at risk for bladder cancer, we investigated possible sex differences in the susceptibility to bladder cancer among smokers.

METHODS

A population-based, case--control study was conducted in Los Angeles, CA, involving 1514 case patients with bladder cancer and 1514 individually matched population control subjects. Information on tobacco use was collected through in-person interviews. Peripheral blood was collected from study participants to measure 3- and 4-aminobiphenyl (ABP)-hemoglobin adducts, a marker of arylamine exposure. Data were analyzed to determine whether the risk of bladder cancer differs between male and female smokers and whether female smokers exhibit higher levels of ABP-hemoglobin adducts than male smokers with comparable smoking habits. All statistical tests were two-sided.

RESULTS

Cigarette smokers had a statistically significant 2.5-fold higher risk (95% confidence interval = 2.1 to 3.0) of bladder cancer than never smokers. Use of filtered versus nonfiltered cigarettes, low-tar versus higher tar cigarettes, or the pattern of inhalation did not modify the risk. The risk of bladder cancer in women who smoked was statistically significantly higher than that in men who smoked comparable numbers of cigarettes (P =.016 for sex-lifetime smoking interaction). Consistent with the sex difference in smoking-related bladder cancer risk, the slopes of the linear regression lines of the 3- and 4-ABP--hemoglobin adducts by cigarettes per day were statistically significantly steeper in women than in men (P values for sex differences <.001 and.006, respectively).

CONCLUSION

The risk of bladder cancer may be higher in women than in men who smoked comparable amounts of cigarettes.

Reevaluation of the confounding effect of cigarette smoking on the relationship between alcohol use and lung cancer risk, with larynx cancer used as a positive control

BACKGROUND

The effect of smoking on lung cancer risk has been well documented, while the effect of alcohol remains controversial. We examined the hypothesis that the apparent association between alcohol intake and lung cancer risk is fully due to the confounding effect of cigarette smoke.

METHODS

Our sample of hospitalized patients included 2,953 male and 1,622 female lung cancer cases; 521 male and 159 female larynx cancers cases; and 8,169 male and 4,154 female controls, admitted to participating hospitals between 1981 and 1994. All controls had been diagnosed with non-smoking-related diseases. Larynx cancer was used as a positive control for lung cancer. Relative risks were estimated through odds ratios, adjusted through multiple logistic regression.

RESULTS

Although the odds ratios for alcohol had been significantly elevated prior to adjustment for smoking (OR = 2.4, 95% CI = 2.0-2.8), alcohol had no effect on lung cancer following this adjustment (OR = 1.2, 95% CI = 1.0-1.4). By contrast, the effect of alcohol on larynx cancer remained high even after adjustment for smoking (OR = 5.6, 95% CI = 3.7-8.6).

CONCLUSION

The often-reported association between alcohol and lung cancer risk can be fully explained by the confounding effect of cigarette use.

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 and cigarette smoking in women: a multicenter case-control study in Europe

The association between cigarette smoking and lung cancer risk in women was investigated within the framework of a case-control study in 9 centres from 6 European countries. Cases were 1,556 women up to 75 years of age with histologically confirmed primary lung cancer; 2, 450 controls with age distribution similar to cases were selected. The predominant cell type was adenocarcinoma (33.5%), with similar proportions for squamous-cell type (26.4%) and small-cell carcinoma (22.3%). Overall, smoking cigarettes at any time was associated with a 5-fold increase in lung cancer risk (odds ratio 5.21, 95% confidence interval 4.49-6.04); corresponding figures for current smoking habits were 8.94, 7.54-10.6. The association showed a dose-response relationship with duration of the habit and daily and cumulative lifetime smoking. A significant excess risk of 70% was associated with every 10 pack-years smoked. After 10 years of smoking cessation, the relative risk decreased to 20% compared to current smokers. The following characteristics were associated with a higher relative risk: inhalation of smoke, smoking non-filter cigarettes, smoking dark-type cigarettes and starting at young age. The association was observed for all major histological types, being the strongest for small-cell type carcinoma, followed by squamous-cell type and the lowest for adenocarcinoma. The proportion of lung-cancer cases in the population attributable to cigarette smoking ranged from 14% to 85%. We concluded that women share most features of the association between cigarette smoking and lung cancer observed in men.

Lung cancer in women: sex-associated differences in survival of patients undergoing resection for lung cancer

STUDY OBJECTIVES

The aim of this study was to analyze various characteristics and survival in female patients treated surgically for lung cancer.

DESIGN

Retrospective clinical study.

PATIENTS

From 1,242 consecutive cases of primary non-small cell lung cancer treated with pulmonary resection between June 1984 and December 1998, 337 female patients (27.1%) were chosen.

RESULTS

Female patients had the following characteristics: a significantly younger age at onset (62.5 +/- 0.56 years vs 64.1 +/- 0.31 years for men), a higher frequency of adenocarcinoma (86.0% vs 48.3% for men), and smaller tumors (32.7 mm vs 38.3 mm in diameter for men). Peripheral tumors were significantly more common in women than men (71.8% vs 50.6%, respectively). Among 686 patients with a history of smoking, the women smoked significantly less often (12.8% vs 91.4% for men). Complete resection was achieved significantly less often in women (79.6% vs 85.2% for men); however, women having complete resection survived significantly longer than their male counterparts. Women with a postoperative negative carcinoembryonic antigen (CEA) had a significantly better prognosis than men; however, women with a postoperative positive CEA did not. Women > or = 60 years old survived significantly longer than their male counterparts, while women < 60 years old did not.

CONCLUSIONS

Once the tumor was resected completely, women survived longer, partly due to the influence of life expectancy. However, the incidence of malignant effusion was higher and the rate of complete resection was lower in women.

Lung cancer in New South Wales: current trends and the influence of age and sex

OBJECTIVE

To examine the effects of time, sex and age at diagnosis on lung cancer incidence rates and the distribution of the histological types of lung cancer in New South Wales.

DESIGN AND SETTING

Retrospective analysis of data from the NSW Cancer Registry and Australian Bureau of Statistics population data for NSW for 1985-1995.

MAIN OUTCOME MEASURES

Trends in lung cancer incidence rates between 1985 and 1995 for men and women aged over 30 years; changes in incidence rates within age groups; and incidence rates of histological subtypes relative to sex and age.

RESULTS

The incidence of lung cancer in men aged 40-80 years fell, while that in women aged over 65 rose. Rates were stable in younger women and older men. Incidence rates in men aged 40-60 years fell by 40%-60%. Were it not for the reduction in incidence rates in men between 1985 and 1995, the number of male lung cancer cases in 1995 would have been greater by 389 (95% CI, 362-415). In women, increasing incidence rates were responsible for an extra 242 cases (95% CI, 232-253) in 1995. Adenocarcinoma comprised a greater percentage of lung cancer cases in younger people, while squamous-cell carcinoma increases steadily with age in both men and women. Women with lung cancer are less likely to have squamous-cell carcinoma (25% for women v. 40% for men) and therefore more likely than men to have adenocarcinoma (35% of new female cases v. 26% for men) or small-cell lung cancer (24% v. 19%).

CONCLUSIONS

Increased smoking cessation has seen a halving of lung cancer rates in middle-aged men. Whether this represents delayed or prevented cases is uncertain. The distribution of histological subtypes of lung cancer in women is different from that in men, and it is not clear whether this difference is hormone-dependent or related to historical patterns of smoking.

Adenocarcinoma of the lung in young patients: the M. D. Anderson experience

BACKGROUND

Surveillance, Epidemiology, and End Results (SEER) data for the years 1973-1992 documented that patients age < 50 years presented with more advanced disease. Because of the increase in the incidence rate of lung adenocarcinoma in the past few decades and the presentation of more advanced disease in young patients, this study was performed to determine whether differences in survival exist between younger and older patients with this disease.

METHODS

The authors reviewed the experience of the University of Texas M. D. Anderson Cancer Center between 1985-1994, encompassing 157 patients age < 40 years of 4097 patients registered with adenocarcinoma of the lung. For comparison, 157 patients age > 50 years with lung adenocarcinoma were selected; these patients were matched for gender, stage of disease at presentation, and definitive therapy modality to assess survival differences more accurately. Data regarding exposure to second-hand smoke were not collected secondary to lack of documentation in the charts reviewed.

RESULTS

There were no significant differences between the 2 groups with regard to the overall survival rate (P = 0.34) or time to progression (P = 0.43). Smoking status (current vs. former vs. never-smoker) was not found to be predictive of survival in either the younger group (P = 0.51) or the older group (P = 0.92).

CONCLUSIONS

The data from the current study indicate that overall survival and disease free survival rates were not significantly different in these two groups. Thus, the younger patient population should be treated similarly to the older patient population. However, a surprisingly high percentage of younger patients were female (45%) and had never smoked (27%), suggesting that risk factors other than active smoking may be involved in lung carcinogenesis in these patients.

Small cell lung cancer in women: risk associated with smoking, prior respiratory disease, and occupation

Small cell carcinoma of the lung (SCLC) occurs most frequently in heavy smokers, yet exhibits a lesser predominance among men than other smoking-associated lung cancers. Incidence rates have increased more rapidly in women than men and at a faster rate among women than other cell types. To investigate the importance of smoking and other risk factors, a case-control study of SCLC in women was conducted. A total of 98 women with primary SCLC and 204 healthy controls, identified by random-digit dialing and frequency matched for age, completed telephone interviews. Data collected include demographics, medical history, family cancer history, residence history, and lifetime smoking habits. Odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated using logistic regression analysis. Risk for small cell carcinoma in women is strongly associated with current use of cigarettes. Ninety-seven of 98 cases had smoked cigarettes; 79% of cases were current smokers and 20% were former smokers at the time of diagnosis compared to 13% current and 34% former smokers among controls. The ORs associated with smoking are 108.7 (95% CI 14.8-801) for ever-use of cigarettes, 278.9 (95% CI 37.0-2102) for current smoking, and 31.5 (95% CI 4. 1-241) for former smoking. Risk increases steeply with pack-years of smoking and decreases with duration of smoking cessation. After adjusting for age, education, and lifetime smoking history, medical history of physician-diagnosed respiratory disease including chronic bronchitis, emphysema, pneumonia, tuberculosis, asthma, and hay fever is not associated with a significant increase in lung cancer risk. Employment in blue collar, service, or other high risk occupations is associated with a two to three-fold non-significant increase in risk for small cell carcinoma after adjusting for smoking.

Cigarette smoking and women's respiratory health

Cigarette smoking is claiming an increasing health toll among women, with rising morbidity and mortality related to lung cancer and COPD. Whether women are more susceptible to the effects of cigarettes with regard to carcinogenesis and development of COPD remains controversial. Gender differences clearly exist in certain aspects of cigarette-related disease, including histologic distribution of lung cancer and the ability of smokers to quit. It is likely that gender differences also exist in the reasons that individuals choose to smoke. Understanding those reasons will be important in developing targeted programs for smoking cessation and in addressing the challenge of the prevention of smoking initiation in women.

Sex-specific expression of gastrin-releasing peptide receptor: relationship to smoking history and risk of lung cancer

BACKGROUND

Activation of gastrin-releasing peptide receptor (GRPR) in human airways has been associated with a proliferative response of bronchial cells to gastrin-releasing peptide and with long-term tobacco use. The GRPR gene is located on the X chromosome and escapes X-chromosome inactivation, which occurs in females. Increasing evidence demonstrates that women are more susceptible than men to tobacco carcinogenesis. We hypothesized that the susceptibility of women to the effects of tobacco may be associated with airway expression of GRPR.

METHODS

We analyzed GRPR messenger RNA (mRNA) expression in lung tissues and cultured airway cells from 78 individuals (40 males and 38 females) and in lung fibroblasts exposed to nicotine in vitro. Nicotinic acetylcholine receptors in airway cells were assayed by use of radioactively labeled nicotine and nicotine antagonists. A polymorphism in exon 2 of the GRPR gene was used to detect allele-specific GRPR mRNA expression in some individuals. Statistical tests were two-sided.

RESULTS

GRPR mRNA expression was detected in airway cells and tissues of more female than male nonsmokers (55% versus 0%) and short-term smokers (1-25 pack-years [pack-years = number of packs of cigarettes smoked per day multiplied by the number of years of smoking]) (75% versus 20%) (P =.018 for nonsmoking and short-term smoking females versus nonsmoking and short-term smoking males). Female smokers exhibited expression of GRPR mRNA at a lower mean pack-year exposure than male smokers (37.4 pack-years versus 56.3 pack-years; P =.037). Lung fibroblasts and bronchial epithelial cells exhibited high-affinity, saturable nicotinic acetylcholine-binding sites. Expression of GRPR mRNA in lung fibroblasts was elevated following exposure to nicotine.

CONCLUSIONS

Our results suggest that the GRPR gene is expressed more frequently in women than in men in the absence of smoking and that expression of this gene is activated earlier in women in response to tobacco exposure. The presence of two expressed copies of the GRPR gene in females may be a factor in the increased susceptibility of women to tobacco-induced lung cancer.

Gender differences in lung cancer risk by smoking: a multicentre case-control study in Germany and Italy

Several studies in the past have shown appreciably higher lung cancer risk estimates associated with smoking exposure among men than among women, while more recent studies in the USA report just the opposite. To evaluate this topic in a European population we conducted a case-control study of lung cancer in three German and three Italian centres. Personal interviews and standardized questionnaires were used to obtain detailed life-long smoking and occupational histories from 3723 male and 900 female cases and 4075 male and 1094 female controls. Lung cancer risk comparing ever-smokers with never-smokers was higher among men (odds ratios (OR) adjusted for age and centre = 16.1, 95% confidence interval (CI) 12.8-20.3) than among women (OR = 4.2, CI 3.5-5.1). Because the smoking habits of women were different from men, we conducted more detailed analyses using comparable levels of smoking exposure. After restriction to smokers and adjustment for other smoking variables, risk estimates did not differ appreciably between genders. The analysis of duration of smoking (0-19, 20-39, 40+ years) adjusted for cigarette consumption and time since quitting smoking revealed similar risk estimates in men (OR = 1.0, 3.3 [CI 2.6-4.2], 4.1 [CI 3.1-5.6]) and women (OR = 1.0, 2.7 [CI 1.7-4.1], 3.3 [CI 1.9-5.8]). The same was true of the analysis of average or cumulative smoking consumption, and also of analyses stratified by different histological types. We conclude that for comparable exposure to tobacco smoke, the risk of lung cancer is comparable in women and men.

Interindividual variability in the expression and NNK carbonyl reductase activity of 11beta-hydroxysteroid dehydrogenase 1 in human lung

The balance between metabolic activation and detoxification is critical in determining the susceptibility to lung cancer upon exposure to the tobacco specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Carbonyl reduction of NNK, followed by glucuronidation, is the main detoxification pathway of this lung carcinogen in humans. Recently, we have identified 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD 1) as microsomal NNK carbonyl reductase in liver and lung. In the present study, the interindividual variability of 11beta-HSD 1 expression and NNK-carbonyl reductase activity was examined in human lung by RT-PCR, Western blot analysis and enzyme activity. Levels of 11beta-HSD 1 mRNA varied over an almost 20-fold range among different subjects. Levels of NNK carbonyl reductase activity in lung microsomes closely resembled the relative amounts of immunoreactive protein as determined by Western blot analysis. In view of the large interindividual differences in the susceptibility of tobacco smoke related lung cancer, we present the first data on the variability of 11beta-HSD 1 expression and NNK carbonyl reduction in human lung.

Molecular epidemiology of lung cancer

Lung cancer occurs through a complex multistage process that results from the combination of carcinogen exposure and genetic susceptibilities. The primary etiology of lung cancer is tobacco smoking, but an understanding of why some smokers develop lung cancer, and others do not, remains unclear. Current studies focus on genetic susceptibilities to lung cancer, and how they modify the effects of tobacco smoke carcinogens. New assays are being developed to study other contributors to cancer risk, such as interindividual differences in DNA repair. There is current evidence to suggest that the risk of lung cancer for women, compared to men, is higher for the same level of smoking. Several biological differences for the types of lung cancer have been observed in women and men. Also, there appear to be differences in lung cancer between Caucasians and African-Americans. Molecular epidemiology tools are uniquely suited to study these biological differences. These studies will improve cancer risk assessments and focus cancer prevention strategies. Other studies also are focusing on tobacco addiction, in order to lead to improved smoking cessation strategies.

Gender-related differences in susceptibility of A/J mouse to benzo[a]pyrene-induced pulmonary and forestomach tumorigenesis

Benzo[a]pyrene (BP) is a suspected human carcinogen and is known to produce tumors in the lung and forestomach of mice. Glutathione (GSH) S-transferases (GST) play a major role in the detoxification of the ultimate carcinogen of BP, (+)-anti-7,8-dihydroxy-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene ((+)-anti-BPDE). Previous studies have shown gender-related differences in the expression of GST isoenzymes in mice. The present study was designed to test the hypothesis whether gender-related differences in the expression of GST isoenzymes can affect the susceptibility of mice to BP-induced lung and forestomach tumorigenesis. The expression of pi class isoenzyme mGSTP1-1, which is highly efficient in the detoxification of (+)-anti-BPDE, was approximately 3.0- and 1.5-fold higher in the liver and forestomach of male A/J mouse, respectively, as compared with the female. The levels of other major GST isoenzymes, mGSTA3-3 (alpha class), mGSTM1-1 (mu class) and mGSTA4-4 (alpha class), were also significantly higher in the liver of the male mouse as compared with the female. While pulmonary mGSTP1-1 expression did not differ significantly between male and female A/J mice, the expression of mGSTA3-3, mGSTM1-1 and mGSTA4-4 was significantly higher (1.4-4.0-fold) in the lung of the male A/J mouse as compared with the female. At lower concentrations of BP (0.5 mg BP/mouse), the tumor incidence/multiplicity was significantly higher in the lung as well as in the forestomach of female mice as compared with male mice. For example, while 30% of the female mice developed pulmonary tumors 26 weeks after the first 0.5 mg BP administration, none of the male mice had tumors in their lungs. At higher doses of BP (1.5 mg BP/mouse), however, this differential was either abolished or relatively less pronounced. Our results suggest that up to a certain threshold of BP exposure the levels of GST isoenzymes may be an important determinant of susceptibility to BP-induced tumorigenesis in mice.

Women and lung cancer: waiting to exhale

Lung cancer is now the leading cause of cancer deaths among women. In the United States, 64,300 women are expected to die of lung cancer in 1996. Smoking is responsible for about 80% of lung cancer cases. Unfortunately, the prevalence of smoking among women remains unacceptably high at about 22% and is expected to surpass the rate in men by the year 2000. Smoking rates are highest among young girls and the less educated. Whether lung cancer represents a different disease in women than in men is unclear. Data are conflicting regarding the magnitude of the relative risk of developing lung cancer due to smoking between the genders. There appears to be a difference in the relative distribution of lung cancer histologic features between men and women that is not explained entirely by differences in smoking patterns. Women who smoke appear to be at higher risk of developing small cell lung cancer than squamous cell lung cancer, whereas men who smoke have a similar risk for the two histologic conditions. Furthermore, women smokers are more likely to develop adenocarcinoma of the lung, and estrogens may play a causative role in this phenomenon. Data are unclear regarding whether the outcome of lung cancer treatment differs between genders. Solutions to the lung cancer epidemic among US women include (1) prevention of the disease by reducing smoking rates, (2) improving early detection methods, and (3) exploring new therapeutic strategies.

Lung carcinoma in former smokers

BACKGROUND

A reduction in the risk of lung carcinoma and a lower death rate among former smokers (FS) compared with current smokers (CS) have been documented in numerous U.S. and international studies. The main objective of our study was to compare the differences in demographic and clinical characteristics in groups stratified by smoking status and gender to evaluate the effect of smoking history and cessation on age at lung carcinoma diagnosis and on specific histologic type.

METHODS

We conducted a cross-sectional study of lung cancer at The University of Texas M.D. Anderson Cancer Center from January 1986 to December 1990 and from January 1992 to December 1993. This study included 1039 patients age 19-88 with confirmed primary lung carcinoma who responded to self-administered risk factor questionnaires. Among them, 497 patients (47.83%) were CS, 444 patients (42.73%) were FS, 98 patients (9.43%) had never smoked (NS), and 840 patients (80.8%) were heavy smokers (more than 20 pack-years).

RESULTS

The median age at lung carcinoma diagnosis for FS was slightly later than that for CS. The histologic type of lung carcinoma for those who had quit smoking more than 20 years previously was not significantly different from that of NS, but was significantly different from that of CS (P < 0.05) and from those who quit smoking fewer than 10 years previously (P < 0.10). CS was a positive predictor for both small cell carcinoma (odds ratio [OR] = 8.79) and squamous cell carcinoma (OR = 2.11) and negatively associated with adenocarcinoma (OR = 0.50), whereas FS was a positive predictor only for small cell carcinoma (OR = 5.50). The variable of pack-years was negatively associated with adenocarcinoma and positively associated with small cell carcinoma in all patients combined and in women, and was also positively associated with squamous carcinoma in all patients after adjustment by smoking status.

CONCLUSIONS

These results indicate that smoking cessation or less life-time smoking exposure affects the distribution of specific histologic subtypes of lung cancer, especially for women, and that smoking cessation may postpone the age at which lung cancer occurs.

A comparative study of the risk factors for lung cancer in Guangdong, China

A case-control study involving 390 lung cancer cases, matched 1:1 with controls, was carried out in Guangdong Province to compare risk factors for different histopathologic types of lung cancer in both sexes. Female and male lung cancers appear to differ in epidemiological characteristics, pathologic types, and risk factors. The 291 lung cancer cases in males were predominantly squamous cell lung carcinoma (squamous cell carcinoma/adenocarcinoma = 1:0.5), whereas the 99 female lung cancer cases were predominantly adenocarcinoma (squamous cell carcinoma/adenocarcinoma = 1:2.7). The age at which lung cancer was first diagnosed was lower for females than for males (P < 0.0001). Single-factor conditional logistic regression analysis showed an association of lung cancer with family history of tumors, family history of lung cancer, history of chronic bronchitis/emphysema, history of tuberculosis, history of other lung disease, smoking, exposure to environmental tobacco smoke (ETS) in the home and in the workplace, being professional drivers, use of oral contraceptives, and consumption of pickled and salted fish (P < 0.05). Further multivariate logistic regression analysis showed that family history of tuberculosis, history of chronic bronchitis/emphysema, family history of tumors, smoking, exposure to ETS in the home and in the workplace, and consumption of pickled and salted fish were independent risk factors for lung cancer. Using log-linear model analysis, it was confirmed that lung cancer had significant interactions with chronic bronchitis/emphysema, exposure to ETS, history of tuberculosis and smoking. Smoking, however, could only explain 1/5 of the incidence of female lung cancers. Family history of lung cancer and the use of oral contraceptives were related to lung cancer in women. Except for a weak relationship with history of chronic bronchitis/emphysema, adenocarcinoma was found to have no association with the other risk factors.

Racial, ethnic, and gender variations in cancer risk: considerations for future epidemiologic research

There is no question that the risk of many cancers varies substantially by race, ethnic group, and gender. Although important clues to cancer etiology may come from investigating the differences in risk across subgroups of the population, epidemiologic research has often focused on white men. More descriptive and analytic studies are needed to identify and explain variations in risk among population subgroups. Especially important are studies to clarify the role of differential exposures, susceptibility, and diagnostic factors in cancer incidence, although differences in treatment may contribute to variations in cancer mortality. Improvements in classification of ethnicity, assessment of carcinogenic exposures in various subpopulations, and measures of host susceptibility states should augment future epidemiologic research designed to better understand mechanisms underlying the racial, ethnic, and gender differences in cancer risk.