Hormonal and reproductive factors and risk of glioma: a prospective cohort study

The etiology of glioma, the most commonly diagnosed malignant brain tumor among adults in the United States, is poorly understood. Given the lower incidence rate of glioma in women than in men, it has been hypothesized that reproductive and hormonal factors may be involved in the etiology of glioma. We conducted a secondary analysis of data from the National Breast Screening Study, which included 89,835 Canadian women, aged 40-59 years at recruitment between 1980 and 1985. Linkages to national cancer and mortality databases yielded data on cancer incidence and deaths from all causes, respectively, with follow-up ending between 1998 and 2000. Cox proportional hazards models were used to estimate hazard ratios and 95% confidence intervals (CI) for the association between hormonal and reproductive factors and risk of glioma. During a mean of 16.4 years of follow-up, we observed 120 incident glioma cases. Compared with women with a relatively early age at menarche (< or =12 years), women who were 13-14 years of age at menarche had a 64% increased risk of glioma (95% CI = 1.01-2.65), and women who were older than 14 years of age at menarche had a 66% increased risk of glioma (95% CI = 0.86-3.20, p(trend) = 0.06). Age at first live birth, parity, menopausal status, use of oral contraceptive and use of hormone replacement therapy were not associated with altered glioma risk in our study population. Additional prospective studies are needed to confirm our findings.     

Cigarette smoking,alcohol intake,and risk of glioma in the NIH-AARP Diet and Health Study

Background:

Although cigarette smoking and alcohol drinking increase the risk of several cancers and certain components of cigarette smoke and alcohol can penetrate the blood–brain barrier, it remains unclear whether these exposures influence the risk of glioma.

Methods:

We examined the associations between cigarette smoking, alcohol intake, and risk of glioma in the National Institutes of Health-AARP Diet and Health Study, a prospective study of 477 095 US men and women ages 50–71 years at baseline. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using models with age as the time metric and adjusted for sex, race/ethnicity, education, and marital status.

Results:

During a median 10.5 person-years of follow-up, 492 men and 212 women were diagnosed with first primary glioma. Among men, current, heavier smoking was associated with a reduced risk of glioma compared with never smoking, but this was based on only nine cases. No associations were observed between smoking behaviours and glioma risk in women. Greater alcohol consumption was associated with a decreased risk of glioma, particularly among men (>2 drinks per day vs <1 drink per week: HR=0.67, 95% CI=0.51–0.90).

Conclusion:

Smoking and alcohol drinking do not appear to increase the risk of glioma.     

A prospective cohort study of cigarette smoking and the risk of endometrial cancer

Case-control studies have shown inverse associations between cigarette smoking and endometrial cancer risk. However, two small prospective cohort studies have not clearly supported an association. Moreover, quantitative measures of smoking have been examined infrequently. Our aim was to study the association between smoking and endometrial cancer risk in a large prospective cohort. We used proportional hazards models to estimate hazard ratios relating cigarette smoking to endometrial cancer risk among 70 591 women aged 40-59 years at recruitment into a randomised controlled trial of mammography screening for breast cancer. During an average of 10.6 years of follow-up (751 833 person-years), a total of 403 women were diagnosed with incident endometrial cancer. We found that a reduced endometrial cancer risk was evident only among women who currently smoked 20 cigarettes per day or more (hazard ratio=0.62, 95% CI=0.42-0.92, P for trend=0.03). There was some suggestion of an inverse association with smoking duration, but this was less clear. The association did not vary with menopausal status, relative body weight, or the use of hormone replacement therapy, but it appeared to be stronger among parous than nulliparous women. The underlying biological mechanisms of this association remain unclear.     

Cigarette smoking, alcohol drinking and the risk of gallbladder cancer death: a prospective cohort study in Japan

Gallbladder cancer is a rare cancer with a poor prognosis, and few risk factors have been identified to date. This prospective study was conducted to evaluate the association of cigarette smoking and alcohol consumption with the risk of gallbladder cancer death. A baseline survey in 45 areas throughout Japan was conducted from 1988 to 1990 using a self-administered questionnaire, and a total of 113,496 participants (65,740 women) aged 40-89 years at entry were followed for 15 years. During the follow-up period, 165 gallbladder cancer deaths (95 women) were observed. Among women, the hazard ratio (HR) [95 percent confidence interval: 95% CI] of current smoker was 2.00 [0.91-4.42], when adjusted for age and drinking. There was no clear association between alcohol consumption and the risk. Among men, HR of current smoker was 2.27 [1.05-4.90]. HRs of those who smoked 21 cigarettes or more per day and those with 801-1,000 cigarette-years were 3.18 [1.18-8.53] and 3.44 [1.40-8.45], respectively, and positive linear associations were observed between that risk and the number of cigarettes per day (p for trend = 0.007) or "cigarette-years" (p for trend = 0.012). The alcohol dose was linearly associated with risk (p for trend = 0.004), where the HR among those who consumed 72.0 g or more of alcohol per day was 3.60 [1.29-9.85]. Among both men and women, cigarette smoking may elevate the risk of death from gallbladder cancer. Drinking may pose an elevated risk among men, but that seems to be less true among women.     

Prospective cohort study of cigarette smoking and colorectal cancer risk in women

Epidemiological studies have consistently found a positive association between cigarette smoking and risk of colorectal adenomas, so the absence of a clear association between smoking and colorectal cancer risk may seem paradoxical. However, if colorectal cancer develops only after an induction period of about 35 years, as has been proposed recently, then studies in which all subjects have fewer than about 35 years between smoking commencement and assessment of outcome would be unlikely to detect this association. Few studies have examined smoking of several decades' duration among women. Therefore, in the cohort study reported here, we used proportional hazards models to estimate hazard ratios relating cigarette smoking to colorectal cancer risk among 89,835 women aged 40-59 years at recruitment into the Canadian National Breast Screening Study, a randomized controlled trial of mammography screening for breast cancer. During an average 10.6 years of follow-up (936,433 person-years), a total of 527 women were diagnosed with incident colorectal cancer (363 colon and 164 rectal). We found that smoking was associated with increased risk of rectal cancer 30 years or more after commencement, and especially with smoking of 40 years' duration or longer (hazard ratio=3.14, 95% CI=1.33-7.42). There was little evidence for altered risk of colon cancer. These results, along with those of other recent studies, support the hypothesis that tobacco smoking is an initiator, rather than a promoter, of rectal cancer. However, the results do not support an association with colon cancer risk, even with smoking of very long duration and high intensity.     

Cigarette smoking and breast cancer risk: update of a prospective cohort study

SummaryIntroduction Ultrasound (US) preoperative examination of the axillary lymph nodes combined with the fine needle aspiration biopsy (FNAB) is often used in order to reduce the number of sentinel lymph node (SLN) biopsy procedures in clinically node negative breast cancer patients. The pathohistological characteristics of the ultrasonically negative axillary lymph nodes in clinically negative axillary lymph nodes are not known. The aim of our study was to compare the pathohistological characteristics of ultrasonically uninvolved axillary lymph nodes (US group) versus clinically uninvolved axillary lymph nodes (non-US group) in SLN biopsy candidates.Methods We included 658 patients after SLN biopsy; 286 patients in the US group and 372 in the non-US group. The pathohistological characteristics of axillary lymph nodes were evaluated by univariate analysis and logistic regression.Results In the univariate analysis, the proportion of macrometastastic SLN, total number of metastatic lymph nodes per patient, proportion of nonsentinel lymph node (NSLN) metastases and proportion of NSLN macrometastases were found to be lower in the US group compared to the non-US group. In the logistic regression model, only US of the axilla (p=0.010; OR: 0.57) and tumor size were significant predictors for the presence of SLN macrometastases or macrometastatic NSLN (p<0.001; OR: 0.23).Conclusion The patients with US negative axillary lymph nodes form a distinct subgroup of early breast cancer patients having a significantly lower tumor burden in the axillary lymph nodes compared to those with only clinically negative axillary lymph nodes.     

Maternal smoking during pregnancy and risk of brain tumors in the offspring. A prospective study of 1.4 million Swedish births

Objective: Studies of the effect of maternal smoking during pregnancy on development of brain tumors in the offspring generally have found no increase in risk but most have mainly relied on retrospective exposure assessment. We conducted a prospective study on a large birth cohort in Sweden. Methods: Women giving birth during 1983–1997 were classified as smokers or non-smokers based on information ascertained at the first prenatal visit and recorded in the Swedish Birth Register. Follow-up of brain tumor incidence among offspring through 1997 was achieved by linkage with the Swedish Cancer Register. Hazard ratios were estimated using Cox proportional hazard regression, adjusting for demographic characteristics available in the Birth Register. Results: Brain tumors (n = 480) occurred at a rate of 4.5 cases per 100,000 person-years. Children of women who smoked during pregnancy had an increased incidence of brain tumors (hazard ratio = 1.24; 95% confidence interval: 1.01–1.53). The increase in risk was similar for benign and malignant tumors, and was most apparent for astrocytoma. The effect of smoking on the occurrence of brain tumors was seen most strongly among 2–4 year-old children. Conclusions: These results support a role for maternal smoking during pregnancy in the etiology of childhood brain tumors. Our findings should be confirmed in other prospective studies.     

Cigarette smoking and risk of histological subtypes of epithelial ovarian cancer in the EPIC cohort study

New data regarding a positive association between smoking and risk of epithelial ovarian cancer (EOC), especially the mucinous tumor type, has started to emerge. The purpose of this study was to examine the association between different measures of smoking exposures and subtypes of EOC in a large cohort of women from 10 European countries. The European Prospective Investigation into Cancer and Nutrition (EPIC) cohort is a multicenter prospective study initiated in 1992. The questionnaires included data about dietary, lifestyle, and health factors. Information about cigarette smoking was collected from individuals in all participating countries. We used Cox proportional hazard regression models to estimate hazard ratio (HR) of EOC overall and serous, mucinous, and endometroid histological subtypes, with 95% confidence intervals (CIs) associated with different measures of smoking exposures adjusting for confounding variables. Altogether 836 incident EOC cases were identified among 326,831 women. The tumors were classified as 400 serous, 83 mucinous, 80 endometroid, 35 clear cell, and 238 unspecified. Compared with never smokers, current smokers had a significantly increased risk for mucinous tumors [HR = 1.85 (95% CI 1.08-3.16)] and those smoking more than 10 cigarettes per day had a doubling in risk [HR = 2.25(95% CI 1.26-4.03)] as did those who had smoked less than 15 pack-years of cigarettes [HR = 2.18 (95% CI 1.07-4.43)]. The results from the EPIC study add further evidence that smoking increases risk of mucinous ovarian cancer and support the notion that the effect of smoking varies according to histological subtype.     

Dietary fiber intake and ovarian cancer risk: a prospective cohort study

There is some evidence from case–control studies that dietary fiber intake might be inversely associated with ovarian cancer risk, but there are limited prospective data. Therefore, we examined ovarian cancer risk in association with intake of dietary fiber in a prospective cohort of 49,613 Canadian women enrolled in the National Breast Screening Study (NBSS), who completed a self-administered food frequency questionnaire between 1980 and 1985. Linkages to national mortality and cancer databases yielded data on deaths and cancer incidence, with follow-up ending between 1998 and 2000. Data from the food frequency questionnaire were used to estimate intake of total dietary fiber, of fiber fractions, and of fiber from various sources. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association between energy-adjusted quartile levels of fiber intake and ovarian cancer risk. During a mean 16.4 years of follow-up, we observed 264 incident ovarian cancer cases. Total dietary fiber and fiber fractions were not associated with ovarian cancer risk in this study population.     

Cigarette smoking and colorectal cancer risk in Germany: a population-based case-control study

Studies have shown fairly consistent positive relationships between smoking and risk of colorectal adenomas, but have yielded inconsistent results for colorectal cancer. Issues relating to the duration, cumulative dose of smoking and the effect of smoking cessation on colorectal cancer risk still need clarification. In a population-based case-control study in Germany, we recruited 540 incident cases of colorectal cancer and 614 controls matched to cases by sex, 5-year age groups and county of residence from January 2003 to June 2004. Subjects were aged>or=30 years, and provided information on risk factors of colorectal cancer, including lifetime cigarette smoking habits, in personal interviews. Odds ratios (OR) and 95% confidence intervals (CI) were computed using conditional logistic regression models, adjusting for potential confounders. Compared with nonsmokers, there was an increased risk for smoking for >or=30 years (OR: 1.25, 95% CI: 0.90-1.75) and a significant risk increase for >or=40 pack-years of smoking (OR: 1.92, 95% CI: 1.13-3.28). Stratification by sex yielded higher risk estimates among females than that among males, with adjusted ORs of 3.5 (95% CI: 1.29-9.52) and 1.15 (0.69-1.91) for women and men, respectively, following >or=30 pack-years of smoking (pinteraction=0.18). Among smokers, risk reduction was observed after >or=20 years of quitting smoking and was significant for >or=40 years (OR: 0.46; 95% CI: 0.21-0.98), when compared to current smokers (p for linear trend=0.05). This study supports the hypothesis that smoking for a long duration at a high cumulative dose increases the risk for colorectal cancer, particularly among women, and suggests that there is risk reduction after longterm smoking cessation.     

A prospective cohort study of cigarette smoking and pancreatic cancer in Japan

Objective: To examine the association of cigarette smoking with the risk of death from pancreatic cancer in a prospective cohort study. Methods: A total of 110,792 inhabitants, aged 40–79 years (46,465 men and 64,327 women), were enrolled from 1988 to 1990 and followed up for mortality to the end of 1997. At baseline a self-administered questionnaire was used to obtain information on cigarette smoking and other lifestyle factors. Results: During the follow-up period (mean ± SD: 8.1 ± 1.8 years), 225 deaths due to pancreatic cancer were identified. After adjustment for age, body mass index, history of diabetes mellitus, and gallbladder diseases, the relative risks (RRs) for current smokers were 1.6 (95% CI 0.95–2.6) in males, and 1.7 (95% CI: 0.84–3.3) in females. Men who smoked more than 40 cigarettes per day had a substantially higher risk of pancreatic cancer, with a RR of 3.3 (95% CI: 1.4–8.1). A significantly decreasing trend in risk with increasing years after smoking cessation was observed (trend p = 0.04) among male ex-smokers. The RRs were 0.85 (95% CI 0.36–2.0) and 0.85 (0.36–2.0) for those who had quit smoking for 10–19 and 20 years, respectively. Conclusions: Our cohort study confirmed that cigarette smoking was associated with an increased risk of death from pancreatic cancer.     

Passive smoking at home and cancer risk: a population-based prospective study in Japanese nonsmoking women

Objective: To study the associations between the intake of flavonols and flavones and the risk of cancer. Methods: The study cohort consisted of 27,110 male smokers, aged 50–69 years, without history of cancer. They were participants of the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study in Finland. The men completed a validated dietary questionnaire at baseline. Incident cases of cancers were identified through national registers. During an average 6.1-year follow-up, 791 lung cancers, 226 prostate cancers, 156 urothelial cancers, 133 colorectal cancers, 111 stomach cancers, and 92 renal cell cancers were diagnosed. Results: Intake of flavonols and flavones was inversely associated with the risk of lung cancer; multivariate relative risk in the highest vs. the lowest quartile 0.56, 95% confidence interval 0.45–0.69, p for trend 0.0001. The risk was similar in all histological types of lung cancer. No association was found between flavonol and flavone intake and the risk of other cancers. Conclusions: Intake of flavonols and flavones seemed to be inversely associated with the risk of lung cancer, but not with that of other cancers.     

Risk factors for thyroid cancer: a prospective cohort study

Given the higher incidence rate of thyroid cancer among women compared to men and evidence that smoking and alcohol consumption may be inversely related to thyroid cancer risk, we examined thyroid cancer risk in association with menstrual, reproductive and hormonal factors, and cigarette and alcohol consumption, in a prospective cohort study of 89,835 Canadian women aged 40-59 at recruitment who were enrolled in the National Breast Screening Study (NBSS). Linkages to national cancer and mortality databases yielded data on cancer incidence and deaths from all causes, respectively, with follow-up ending between 1998 and 2000. Cox proportional hazards models (using age as the time scale) were used to estimate hazard ratios and 95% confidence intervals for the association between each of the potential risk factors and risk of thyroid cancer overall and by the main histologic subtypes. During a mean of 15.9 years of follow-up, we observed 169 incident thyroid cancer cases. There was no evidence of altered overall thyroid cancer risk with any of the menstrual, reproductive, or hormonal factors. There was evidence of a decreased risk of papillary thyroid cancer among women with 5 or more live births (vs. nulliparous). Age at which smoking commenced, duration of smoking, number of cigarettes smoked per day, pack-years of smoking and alcohol consumption were not associated with altered thyroid cancer risk. The present study provides little support for associations with hormonal factors, smoking, or alcohol consumption, but there is a need for additional prospective data.     

吸烟与原发性肝癌关系的巢式病例对照研究

目的 分析吸烟与上海市区中老年男性原发性肝癌的关系.方法 应用巢式病例对照研究方法,对一个18 244名男性队列随访11年,以队列中213例新发肝癌患者作为病例组,按照患者年龄、采样日期、同居住区等配对条件,从队列中随机抽取1094名健康人作为对照组.使用配对Logistic回归分析,调整可能的混杂因素,估计吸烟对肝癌发生的危险度和95%可信区间(CI).结果 调整肝炎、肝硬化、胆石症或其他胆囊病史及乙型肝炎病毒感染等可能的混杂因素后,男性吸烟者患肝痛的危险性是不吸烟者的1.91倍(95%CI为1.28～2.86),日随着每天吸烟量、吸烟年限和吸烟包年数的增加而增加.每天吸烟≥20支者、吸烟≥40年者和吸烟37包年者患肝癌的相对危险度分别为2.16(95%CI为1.37～3.40)、2.14(95%CI为1.18～3.87)和2.12(95%CI为1.21～3.74).吸烟开始年龄越小,危险性越大,吸烟开始年龄<20岁者患肝癌的危险性为2.57(95%CI为1.50～4.40).结论 吸烟是上海市区男性原发性肝癌的危险因素.     

Active and passive smoking and breast cancer risk in middle-aged Japanese women

To examine the hypothesis that tobacco smoke is associated with the risk of female breast cancer, we estimated the relative risks of active and passive smoke in middle-aged Japanese women in a population-based prospective study. The cohort consisted of residents in 4 public health center areas, aged 40 to 59 years. A self-administered questionnaire survey was conducted in 1990. This analysis included 21,805 subjects, 180 of whom had developed breast cancer by December 31, 1999. When the reference was defined as never-active smokers without passive smoking, adjusted relative risks (RRs) were 1.9 (95% confidence interval [CI] = 1.0-3.6) in current active smokers, 1.2 (95% CI = 0.4-4.0) in ex-active smokers and 1.2 (95% CI = 0.8-1.6) in never-active smokers with passive smoking. The elevated risk for ever-smokers was clearly observed in premenopausal women at baseline (RR = 3.9, 95% CI = 1.5-9.9) but not in postmenopausal women (RR = 1.1, 95% CI = 0.5-2.5). In never-active smokers, the adjusted RR for passive smoking, residential or occupational/public tobacco smoke exposure was 1.1 (95% CI = 0.8-1.6). In premenopausal women, passive smoking increased the risk (RR = 2.6; 95% CI = 1.3-5.2) but not in postmenopausal women (RR = 0.7; 95% CI = 0.4-1.0). We conclude that tobacco smoking increases the risk of female breast cancer in premenopausal women.     

Associations of cigarette smoking and alcohol drinking with stomach cancer survival: A prospective patient cohort study in Japan

Cigarette smoking and alcohol drinking may affect the prognosis of stomach cancer, but evidence has been inconsistent. We investigated the associations between pretreatment smoking and alcohol drinking and the risk of all‐cause and stomach cancer death among 1,576 patients with histologically confirmed stomach cancer diagnosed during 1997–2010 at a single hospital in Japan. Histories of smoking and alcohol drinking were assessed using a self‐administered questionnaire. The patients were followed until December 31, 2013. The Cox proportional hazards model was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). During 9,625.1 person‐years, 670 all‐cause and 419 stomach cancer deaths were documented. Among the patients overall, ever‐drinking was significantly associated with an increased risk of all‐cause death (HR: 1.25; 95% CI: 1.03–1.51), but not stomach cancer death. Positive linear associations with the frequency of drinking (p_trend = 0.02) and the amount of alcohol consumed per day (p_trend = 0.03) were observed for the risk of all‐cause death. Ever‐smoking was not related to either the risk of all‐cause or stomach cancer death. Conversely, among the patients who underwent curative resection, a significant positive association was found between ever‐smoking and the risk of stomach cancer death (HR: 2.44; 95% CI: 1.17–5.08). A positive association was also found for earlier age at start of smoking (p_trend = 0.0046). Pretreatment smoking and alcohol drinking have significant effects on stomach cancer survival. Lifestyle adjustments throughout life may improve survival.     

Cohort studies of association between self-reported allergic conditions,immune-related diagnoses and glioma and meningioma risk

An inverse association between self-reported allergies and glioma and meningioma risk, has been previously observed in case-control studies. Approximately 27% (median) of the information on both glioma and meningioma in these studies, however, is collected from proxy respondents. In fact, the odds ratios (OR) among previous brain tumor studies are inversely related to the proportion of proxy respondents (Pearson correlation coefficient = -0.94; 95% CI = -1.00 to -0.65); this correlation suggests bias. We therefore constructed 3 cohorts based on the Swedish Twin, Hospital Discharge, and Cancer Registries. In Cohorts I (14,535 people developed 37 gliomas and 41 meningiomas) and II (29,573 people developed 42 gliomas and 26 meningiomas) median time from self-report of allergies to brain tumor diagnosis was 15.4 years. Cohort III, which overlaps with Cohorts I and II (52,067 people developed 68 gliomas and 63 meningiomas), was linked to the Swedish Hospital Discharge Registry where pre-brain tumor immune-related discharge diagnoses were recorded. Allergies are inversely associated with glioma risk in Cohort I (Hazard ratio [HR] = 0.45; 95% CI = 0.19-1.07) and among high grade (III and IV, HR = 0.45; 95% CI = 0.11-1.92) but not low grade (I and II, HR = 2.60; 95% CI = 0.86-7.81) gliomas in Cohort II. In Cohort III, immune-related discharge diagnoses are also inversely associated with glioma (HR = 0.46; 95% CI = 0.14-1.49). There is no strong evidence against (and some for) the hypothesis that allergies reduce glioma risk.     

Cigarette smoking during pregnancy and preeclampsia risk: a systematic review and meta-analysis of prospective studies

Although evidence from epidemiological studies evaluating the association between cigarette smoking during pregnancy and preeclampsia risk has been systematically reviewed, the findings have been out of date. To further clarify the relationship, we conducted this comprehensive meta-analysis of prospective studies. We searched PubMed and Web of Science up to August 2015 to identify prospective studies that evaluated the association between cigarette smoking during pregnancy and preeclampsia risk. Random-effects models were used to estimate summarized relative risk (RR) and 95% confidence intervals (CIs). Seventeen prospective studies involving 62,089 preeclampsia patients from a total of approximately 1.8 million subjects were included. Overall, there was a significant negative association between smoking during pregnancy and incidence of preeclampsia (RR = 0.67, 95% CI: 0.60–0.75), with significant heterogeneity (I² = 91.7%). Such an inverse association was also detected in strata of subgroup analyses according to study location, study sample size, parity of populations, singleton pregnancy, and adjustment for potential confounders including maternal age, diabetes mellitus, chronic hypertension, body mass index, and gender of infant. In summary, this meta-analysis suggests that smoking during pregnancy is inversely associated with incidence of preeclampsia. Further large scale multi-center prospective studies are warranted to validate our findings.     

Cigarette smoking and the risk of invasive epithelial ovarian cancer in a prospective cohort study

Few cohort studies have examined the association between cigarette smoking and ovarian cancer risk, either overall, or by histological subtype. In relation to the latter, it has been suggested that mucinous ovarian tumours may be aetiologically unrelated to the other types of epithelial tumours and that their respective associations with cigarette smoking may differ. We examined the association between smoking and ovarian cancer risk using data from participants in a randomised controlled trial of screening for breast cancer involving 89,835 women aged 40-59 years at recruitment. Cox proportional hazards models were used to estimate rate ratios (RR) and 95% confidence intervals (CI). During an average of 16.5 years of follow-up, we observed 454 incident cases of ovarian cancer (184 serous, 67 endometrioid, 32 mucinous, 171 other or unknown). We found that women who had smoked for several decades had an approximately two-fold increased risk of epithelial ovarian cancer. Relative to never-smokers, women who had smoked for 40 years or more were at the highest risk (RR=2.50, 95% CI=1.37-4.56). The association with non-mucinous tumours was similar to that observed overall. For mucinous tumours, a two-fold increased risk was observed with smoking of shorter duration, although the number of mucinous tumours in our data-set was small. Long-term cigarette smoking may be associated with an increased risk of epithelial ovarian tumours.     

Cigarette smoking and breast cancer risk among young women (United States)

Objectives: To evaluate whether heavy cigarette smoking as a teenager or long-term smoking increases breast cancer risk or, alternatively, whether smoking acts as an anti-estrogen and reduces risk.Methods: Data from a multi-center, population-based, case-control study among women under age 55 were analyzed.Results: Among women under age 45, there was a modest inverse relation with current (OR=0.82, 95% CI=0.67, 1.01) but not past (OR=0.99, 95% CI=0.81, 1.21) smoking. Odds ratios were decreased for current smokers who began at an early age (0.59 for15, 95% CI=0.41, 0.85) or continued for long periods of time (0.70 for >21 years, 95% CI=0.52, 0.94). In subgroup analyses, reduced odds ratios were observed among current smokers who were ever users of oral contraceptives (0.79, 95% CI=0.63, 0.98), were in the lowest quartile of adult body size (0.53, 95% CI=0.34, 0.81), or never or infrequently drank alcohol (0.68, 95% CI=0.47, 0.98). Among women ages 45-54, there was little evidence for an association with smoking.Conclusions: These results suggest that breast cancer risk among women under age 45 may be reduced among current smokers who began smoking at an early age, or long-term smokers, but require confirmation from other studies.