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

Premature ovarian insufficiency: a review on the role of tobacco smoke, its clinical harm, and treatment

Premature ovarian insufficiency (POI) is a condition in which the quantity of follicles and the quality of oocytes gradually decrease. This results in an estrogen secretion disorder and abnormal follicle development, which can lead to related diseases, early onset of menopause, sexual dysfunction, and an increased risk of cardiovascular issues, osteoporosis, and depression, among others. This disease significantly impacts the physical and mental health and overall quality of life of affected women. Factors such as genetic abnormalities, oophorectomy, radiotherapy for malignancy, idiopathic conditions, and an unhealthy lifestyle, including smoking, can accelerate the depletion of the follicular pool and the onset of menopause. Extensive research has been conducted on the detrimental effects of tobacco smoke on the ovaries. This article aims to review the advancements in understanding the impact of tobacco smoke on POI, both in vivo and in vitro. Furthermore, we explore the potential adverse effects of common toxicants found in tobacco smoke, such as polycyclic aromatic hydrocarbons (PAHs), heavy metals like cadmium, alkaloids like nicotine and its major metabolite cotinine, benzo[a]pyrene, and aromatic amines. In addition to discussing the toxicants, this article also reviews the complications associated with POI and the current state of research and application of treatment methods. These findings will contribute to the development of more precise treatments for POI, offering theoretical support for enhancing the long-term quality of life for women affected by this condition.

Critical review of the association between perineal use of talc powder and risk of ovarian cancer

Over the past four decades, there has been increasing concern that perineal use of talc powder, a commonly used personal care product, might be associated with an increased risk of ovarian cancer.

OBJECTIVES

To critically review all available human epidemiological data on the relationship between perineal use of talc powder and ovarian cancer, with consideration of other relevant experimental evidence.

METHODOLOGY

We identified 30 human studies for qualitative assessment of evidence, including 27 that were retained for further quantitative analysis.

RESULTS

A positive association between perineal use of talc powder and ovarian cancer was found [OR: 1.28 (95% CI: 1.20-1.37)]. A significant risk was noted in Hispanics and Whites, in women applying talc to underwear, in pre-menopausal women and in post-menopausal women receiving hormonal therapy. A negative association was noted with tubal ligation.

CONCLUSION

Perineal use of talc powder is a possible cause of human ovarian cancer.

Association between Cigarette Smoking and Histotype-Specific Epithelial Ovarian Cancer: A Review of Epidemiologic Studies

Many studies have demonstrated that smoking can influence ovarian cancer risk and survival; however, the number of studies investigating this relationship according to histologic subtypes is limited. We conducted a review of epidemiologic research that assessed the role of smoking on ovarian cancer risk and survival after diagnosis, specifically capturing studies that discerned between various histologic subtypes of this disease. In the majority of studies, current smoking was associated with increased risk of mucinous cancer. There was also evidence of a decreased risk of clear cell and endometrioid histotypes. No significant association was observed between cigarette smoking and serous cancer. In the studies investigating the relationship between smoking and survival, all the studies reported an increased risk of mortality associated with smoking. Smoking appeared to be a risk factor for both ovarian cancer risk and mortality. Future studies need to investigate further a potential link between smoking and ovarian cancer by having a better assessment of exposure to smoking and having a larger number of participants with the ability to detect associations within rare histotypes.

Dose-risk relationships between cigarette smoking and ovarian cancer histotypes: a comprehensive meta-analysis

PURPOSE

Although smoking has not been associated with overall ovarian cancer risk, a different impact on various histotypes has been reported. Our aim is to provide an accurate, up-to-date estimate of the dose-risk relationships between cigarette smoking and epithelial ovarian cancer, overall and by histotypes.

METHODS

Using an innovative approach for the identification of original study publications, we conducted a systematic review and meta-analysis of epidemiological studies published on the topic until September 2018. Summary relative risks (RR) for cigarette smoking were estimated using random-effects models; dose-risk relationships were evaluated using one-stage random-effects models with restricted cubic splines.

RESULTS

Thirty-seven studies were considered in the meta-analysis. The summary RRs for current versus never smokers were 1.05 (95% confidence interval CI 0.95-1.16) for overall ovarian cancer, 1.78 (95% CI 1.52-2.07) for mucinous, 0.77 (95% CI 0.65-0.93) for clear cell, 0.81 (95% CI 0.73-0.91) for endometrioid, and 1.05 (95% CI 0.94; 1.17) for serous cancer. The risk of borderline mucinous (RR 2.09) and serous (RR 1.16) tumors was higher than for invasive cancers (RR 1.44 and 0.95, respectively). For mucinous cancer, risk was noticeably higher with smoking intensity and duration (RR 2.35 for 20 cigarettes/day, and 2.11 for 20 years of smoking). A non-significant linear relation was found with smoking intensity, duration, and time since quitting for overall ovarian cancer and other histotypes.

CONCLUSIONS

This uniquely large and comprehensive meta-analysis confirms that although cigarette smoking does not appear to be a risk factor for ovarian cancer, and it is even slightly protective for some rare histotypes, there is a strong dose-risk relationship with mucinous ovarian cancer.

Cigarette smoking and the association with serous ovarian cancer in African American women: African American Cancer Epidemiology Study (AACES)

BACKGROUND

Smoking is a risk factor for mucinous ovarian cancer (OvCa) in Caucasians. Whether a similar association exists in African Americans (AA) is unknown.

METHODS

We conducted a population-based case-control study of incident OvCa in AA women across 11 geographic locations in the US. A structured telephone interview asked about smoking, demographic, health, and lifestyle factors. Odds ratios and 95% confidence intervals (OR, 95% CI) were estimated from 613 cases and 752 controls using unconditional logistic regression in multivariable adjusted models.

RESULTS

Associations were greater in magnitude for serous OvCa than for all OvCa combined. Compared to never smokers, increased risk for serous OvCa was observed for lifetime ever smokers (1.46, 1.11-1.92), former smokers who quit within 0-2 years of diagnosis (5.48, 3.04-9.86), and for total pack-years smoked among lifetime ever smokers (0-5 pack-years: 1.79, 1.23-2.59; >5-20 pack-years: 1.52, 1.05-2.18; >20 pack-years: 0.98, 0.61-1.56); however, we observed no dose-response relationship with increasing duration or consumption and no significant associations among current smokers. Smoking was not significantly associated with mucinous OvCa. Associations for all OvCa combined were consistently elevated among former smokers. The proportion of ever smokers who quit within 0-2 years was greater among cases (23%) than controls (7%).

CONCLUSIONS

Cigarette smoking may be associated with serous OvCa among AA, which differs from associations reported among Caucasians. Exposure misclassification or reverse causality may partially explain the absence of increased risk among current smokers and lack of dose-response associations. Better characterization of smoking patterns is needed in this understudied population.

Smoking and risk of ovarian cancer by histological subtypes: an analysis among 300 000 Norwegian women

BACKGROUND

We prospectively investigated the association between different measures of smoking exposure and the risk of serous, mucinous, and endometrioid ovarian cancers (OC) in a cohort of more than 300 000 Norwegian women.

METHODS

We followed 300 398 women aged 19-67 years at enrolment until 31 December 2013 for OC incidence through linkage to national registries. We used Cox proportional hazards models with attained age as the underlying time scale to estimate multivariable-adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) adjusted for relevant confounders.

RESULTS

During more than 5.9 million person-years and a median follow-up time of 19 years, 2336 primary invasive (1647, 71%) and borderline (689, 29%) OC were identified (53% serous, 19% mucinous). Compared with never smokers, current smokers who had smoked for ⩾10 years had a higher risk of mucinous OC (HR10-19 years vs never=1.73, 95% CI 1.24-2.42; HR⩾20 vs never=2.26, 95% CI 1.77-2.89, Ptrend <0.001). When stratified by invasiveness, current smokers had a higher risk of invasive mucinous OC (HR=1.78, 95% CI 1.20-2.64) and borderline mucinous OC (HR=2.26 95% CI, 1.71-2.97) (Pheterogeneity=0.34) than never smokers. Smoking was not associated with serous or endometrioid OC.

CONCLUSIONS

Using a very large cohort of women, the current analysis provides an important replication for a similar risk of invasive and borderline mucinous OC related to smoking.

Cancer incidence attributable to tobacco in Alberta, Canada, in 2012

BACKGROUND

Strong and consistent epidemiologic evidence shows that tobacco smoking causes cancers at various sites. The purpose of this study was to quantify the proportion and total number of site-specific cancers in Alberta attributable to tobacco exposure.

METHODS

The proportion of incident cancer cases attributable to active and passive tobacco exposure in Alberta was estimated with population attributable risks. Data from the Canadian Community Health Survey (CCHS) for 2000-2007 were used to estimate prevalence of active (current or former smoker) and passive (second-hand smoke) tobacco exposure in Alberta.

RESULTS

According to the 2000/01 CCHS, 29.1% and 38.6% of Albertans were estimated to be current and former smokers, respectively. According to the 2003 CCHS, 23.7% of Albertans who had never smoked reported regular second-hand exposure to tobacco. Population attributable risk estimates for tobacco-related cancer sites ranged from about 4% for ovarian cancer to 74% for laryngeal cancer. About 5% of incident lung cancers in men and women who never smoked could be attributed to passive tobacco exposure. Overall, 37.0% of tobacco-related cancers in Alberta (or 15.7% of all cancers) were estimated to be attributable to active tobacco smoking in 2012.

INTERPRETATION

A notable proportion of cancers associated with tobacco use were estimated to be attributable to active smoking in Alberta. Strategies to reduce the prevalence of active tobacco smoking in Alberta could have a considerable impact on future cancer incidence.

Epithelial ovarian cancer subtypes attributable to smoking in the Norwegian Women and Cancer Study, 2012

Among European women, ovarian cancer is the fifth most common cancer. Smoking is an established risk factor for mucinous tumors. We estimated the impact of smoking in Norwegian women using population attributable fractions (PAFs) of epithelial ovarian cancer (EOC), by invasiveness and by histological subtypes in the Norwegian Women and Cancer Study with an average of 13.2 years of follow‐up. During >2 million person‐years, a total of 915 incident EOC cases, of which 667 (73%) invasive and 248 (27%) borderline, were identified among 154,234 women aged 34–70 years at enrolment. Compared with never smokers, current smokers had a nonstatistically significant increased risk of mucinous tumors (hazard ratio [HR] = 1.67 [95% confidence interval, (CI), 0.96–2.96]) and more than twice statistically significant risk of borderline mucinous tumors (HR = 2.17 [95% CI, 1.06–4.45]). The corresponding PAF estimates were 16.5% for mucinous and 25% for borderline mucinous. We found that among middle‐aged women, one in six mucinous tumors and one in four borderline mucinous tumors could have been prevented if women did not smoke.

Intake of vitamins A, C, and E and folate and the risk of ovarian cancer in a pooled analysis of 10 cohort studies

PURPOSE

Vitamins A, C, and E and folate have anticarcinogenic properties and thus might protect against cancer. Few known modifiable risk factors for ovarian cancer exist. We examined the associations between dietary and total (food and supplemental) vitamin intake and the risk of invasive epithelial ovarian cancer.

METHODS

The primary data from 10 prospective cohort studies in North America and Europe were analyzed. Vitamin intakes were estimated from validated food frequency questionnaires in each study. Study-specific relative risks (RRs) were estimated using the Cox proportional hazards model and then combined using a random-effects model.

RESULTS

Among 501,857 women, 1,973 cases of ovarian cancer occurred over a median follow-up period of 7-16 years across studies. Dietary and total intakes of each vitamin were not significantly associated with ovarian cancer risk. The pooled multivariate RRs [95% confidence intervals (CIs)] for incremental increases in total intake of each vitamin were 1.02 (0.97-1.07) for vitamin A (increment: 1,300 mcg/day), 1.01 (0.99-1.04) for vitamin C (400 mg/day), 1.02 (0.97-1.06) for vitamin E (130 mg/day), and 1.01 (0.96-1.07) for folate (250 mcg/day). Multivitamin use (vs. nonuse) was not associated with ovarian cancer risk (pooled multivariate RR = 1.00, 95% CI 0.89-1.12). Associations did not vary substantially by study, or by subgroups of the population. Greater vitamin intakes were associated with modestly higher risks of endometrioid tumors (n = 156 cases), but not with other histological types.

CONCLUSION

These results suggest that consumption of vitamins A, C, and E and folate during adulthood does not play a major role in ovarian cancer risk.

Association between alcohol consumption and the risk of ovarian cancer: a meta-analysis of prospective observational studies

Background

Alcohol consumption has been inconsistently associated with the risk of ovarian cancer. The purpose of this study was to summarize the data from prospective cohort studies on the relationship between alcohol consumption and ovarian cancer using a meta-analytic approach.

Methods

We performed electronic searches of PubMed, Embase, and the Cochrane Library in May 2014 to identify studies that examined the effects of alcohol consumption on the incidence of ovarian cancer. Only prospective cohort studies that reported effect estimates about the incidence of ovarian cancer with 95% confidence intervals (CIs) of alcohol intake were included.

Results

Collectively, we included 13 prospective studies that reported on data from 1,996,841 individuals and included 5,857 cases of ovarian cancer. Alcohol consumption had little to no effect on ovarian cancer incidence when compared to non-drinkers (risk ratio [RR], 1.03; 95% CI, 0.96–1.10; P = 0.473). Similarly, low (RR, 0.96; 95% CI, 0.93–1.00; P = 0.059), moderate (RR, 1.08; 95% CI, 0.92–1.27; P = 0.333), and heavy (RR, 0.99; 95% CI, 0.88–1.12; P = 0.904) alcohol consumption was not associated with the risk of ovarian cancer. Furthermore, subgroup analyses suggested that low alcohol intake was associated with a reduced risk of ovarian cancer whereas heavy alcohol intake was associated with an increased risk of ovarian cancer in multiple subpopulations.

Conclusions

Our study suggests that alcohol intake is not associated with an increased risk of ovarian cancer. Subgroup analyses indicated that alcohol consumption might be associated with the risk of ovarian cancer in specific population or in studies with specific characteristics.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-1355-8) contains supplementary material, which is available to authorized users.

Is cancer risk still reduced if you give up smoking in later life?

SUMMARY This report summarizes the experimental and epidemiological evidence examining the ability of smoking cessation to influence cancer risk reduction in later life. Available evidence suggests that smoking cessation even in later years can significantly reduce mortality and yield risk reductions for many cancers including lung, oral, head and neck, and stomach cancer, among others. More research is necessary to accurately quantify the degree of cancer risk reduction for particular age groups and to calculate the minimum time of cessation necessary to produce a significant benefit for the patient. Smoking cessation is the only approach that has been shown to effectively reduce the risk of many cancers on a mass scale. Considering this, we recommend that healthcare providers communicate these benefits to patients at every opportunity and reinforce the notion that it is never too late to quit smoking.

Cigarette smoking and risk of ovarian cancer: a pooled analysis of 21 case-control studies

PURPOSE

The majority of previous studies have observed an increased risk of mucinous ovarian tumors associated with cigarette smoking, but the association with other histological types is unclear. In a large pooled analysis, we examined the risk of epithelial ovarian cancer associated with multiple measures of cigarette smoking with a focus on characterizing risks according to tumor behavior and histology.

METHODS

We used data from 21 case-control studies of ovarian cancer (19,066 controls, 11,972 invasive and 2,752 borderline cases). Study-specific odds ratios (OR) and 95 % confidence intervals (CI) were obtained from logistic regression models and combined into a pooled odds ratio using a random effects model.

RESULTS

Current cigarette smoking increased the risk of invasive mucinous (OR = 1.31; 95 % CI: 1.03-1.65) and borderline mucinous ovarian tumors (OR = 1.83; 95 % CI: 1.39-2.41), while former smoking increased the risk of borderline serous ovarian tumors (OR = 1.30; 95 % CI: 1.12-1.50). For these histological types, consistent dose-response associations were observed. No convincing associations between smoking and risk of invasive serous and endometrioid ovarian cancer were observed, while our results provided some evidence of a decreased risk of invasive clear cell ovarian cancer.

CONCLUSIONS

Our results revealed marked differences in the risk profiles of histological types of ovarian cancer with regard to cigarette smoking, although the magnitude of the observed associations was modest. Our findings, which may reflect different etiologies of the histological types, add to the fact that ovarian cancer is a heterogeneous disease.

Glutathione-deficient mice have increased sensitivity to transplacental benzo[a]pyrene-induced premature ovarian failure and ovarian tumorigenesis

Polycyclic aromatic hydrocarbons (PAH) such as benzo[a]pyrene (BaP) are ubiquitous environmental pollutants found in tobacco smoke, air pollution, and grilled foods. Prenatal exposure to BaP causes premature reproductive senescence in mice, and other PAHs are transplacental ovarian carcinogens. Glutathione (GSH) is critical for detoxification of the reactive metabolites of PAHs. Therefore, we hypothesized that mice that are genetically deficient in GSH synthesis, due to deletion of the modifier subunit of glutamate cysteine ligase (Gclm), the rate-limiting enzyme in GSH synthesis, have increased destruction of oogonia, premature ovarian failure, and ovarian tumorigenesis after transplacental BaP exposure compared with Gclm(+/+) females. Gclm(+/-) female and male mice were mated, and dams were treated with 0, 2, or 10 mg/kg/d BaP in sesame oil by gavage from gestational days 7 to 16. Compared with oil-treated F1 females of the same genotype, Gclm(-/-) prenatally BaP-treated females had significantly greater decrements in offspring production than Gclm(+/+) BaP-treated females. Similarly, we observed significant BaP dose × Gclm genotype interactions on ovarian follicle counts and ovarian tumor multiplicity at 7.5 months of age, with Gclm(-/-) females having greater decrements in follicle numbers and more ovarian tumors in response to prenatal BaP exposure than Gclm(+/+) females. The ovarian tumors were positive for the epithelial marker cytokeratin. Our results show that prenatal exposure of females to BaP causes premature ovarian failure and ovarian tumorigenesis and that embryonic GSH deficiency due to deletion of Gclm increases sensitivity to these transplacental ovarian effects of BaP.

Ovarian cancer and smoking: individual participant meta-analysis including 28,114 women with ovarian cancer from 51 epidemiological studies

Background

Smoking has been linked to mucinous ovarian cancer, but its effects on other ovarian cancer subtypes and on overall ovarian cancer risk are unclear, and the findings from most studies with relevant data are unpublished. To assess these associations, we review the published and unpublished evidence.

Methods

Eligible epidemiological studies were identified by electronic searches, review articles, and discussions with colleagues. Individual participant data for 28 114 women with and 94 942 without ovarian cancer from 51 epidemiological studies were analysed centrally, yielding adjusted relative risks (RRs) of ovarian cancer in smokers compared with never smokers.

Findings

After exclusion of studies with hospital controls, in which smoking could have affected recruitment, overall ovarian cancer incidence was only slightly increased in current smokers compared with women who had never smoked (RR 1·06, 95% CI 1·01–1·11, p=0·01). Of 17 641 epithelial cancers with specified histology, 2314 (13%) were mucinous, 2360 (13%) endometrioid, 969 (5%) clear-cell, and 9086 (52%) serous. Smoking-related risks varied substantially across these subtypes (p_{heterogeneity}<0·0001). For mucinous cancers, incidence was increased in current versus never smokers (1·79, 95% CI 1·60–2·00, p<0·0001), but the increase was mainly in borderline malignant rather than in fully malignant tumours (2·25, 95% CI 1·91–2·65 vs 1·49, 1·28–1·73; p_{heterogeneity}=0·01; almost half the mucinous tumours were only borderline malignant). Both endometrioid (0·81, 95% CI 0·72–0·92, p=0·001) and clear-cell ovarian cancer risks (0·80, 95% CI 0·65–0·97, p=0·03) were reduced in current smokers, and there was no significant association for serous ovarian cancers (0·99, 95% CI 0·93–1·06, p=0·8). These associations did not vary significantly by 13 sociodemographic and personal characteristics of women including their body-mass index, parity, and use of alcohol, oral contraceptives, and menopausal hormone therapy.

Interpretation

The excess of mucinous ovarian cancers in smokers, which is mainly of tumours of borderline malignancy, is roughly counterbalanced by the deficit of endometrioid and clear-cell ovarian cancers. The substantial variation in smoking-related risks by tumour subtype is important for understanding ovarian carcinogenesis.

Funding

Cancer Research UK and MRC.

Induction of ovarian cancer and DNA adducts by Dibenzo[a,l]pyrene in the mouse

Tobacco smoking is an etiological factor of ovarian cacner; however, the mechanisms remain largely undefined. Therefore, as an initial investigation, we examined the carcinogenicity and DNA adducts formation in the ovary of mice treated with DB[a,l]P, a tobacco smoke constituent and environmental pollutant. Ovarian tumors in B6C3F1 mice were induced by direct application of DB[a,l]P (24, 12, 6, and 3 nmol/mouse, three times a week for 38 weeks) into the oral cavity of mice. At 6 nmol, DB[a,l]P induced the highest total ovarian tumor incidence (79%), but the incidence of malignancy was only 15%. However, at the dose of 12 nmol, the total ovarian tumor incidence was 75%, and the incidence of malignancy was 65%. In addition to ovarian tumors, at the dose of 24 nmol, DB[a,l]P induced lesions in sites distal from the ovaries including the skin, mammary, lung, and oral tissues, which were rare at doses lower than 24 nmol. Another bioassay was conducted to detect and quantify DNA adducts induced by DB[a,l]P (24 nmol, three times a week for 5 weeks) in the ovary at 48 h and 1, 2, and 4 weeks after the last administration of DB[a,l]P. DNA was isolated, and the dibenzo[a,l]pyrene-11,12-dihydrodiol-13,14-epoxide (DB[a,l]PDE)-DNA adducts were analyzed by a LC-MS/MS method. DB[a,l]P resulted in the formation of (-)-anti-cis-DB[a,l]PDE-dA and (-)-anti-trans-DB[a,l]PDE-dA adducts, which were 0.8 and 1.6 fmol/10(6) dA, respectively, in ovaries of mice within 48 h, and the level of adducts decreased over a week. Our results indicated that DB[a,l]P can be metabolized to form (-)-anti-DB[a,l]PDE; the latter may, in part, account for DB[a,l]P-induced ovarian cancer. This animal model should assist to better understand the mechanisms, account for the induction of ovarian cancer by tobacco carcinogens, and facilitate the development of chemopreventive agents against ovarian cancer.

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.

Epidemiological and genetic factors associated with ovarian cancer

The purpose of this article was to provide a comprehensive review of the epidemiological and genetic factors associated with ovarian cancer. A more complete understanding of the determinants of ovarian cancer may lead to the development of better screening and detection methods for this disease. The first section of this article reviews current literature on screening and early detection of ovarian cancer. The second section reviews the epidemiology of ovarian cancer, specifically highlighting the risk factors associated with the development of this disease. The article concludes with a discussion of how oncology nurses can apply this information to improve patient care.

Height, body mass index, and ovarian cancer: a pooled analysis of 12 cohort studies

BACKGROUND

Although many studies have investigated the association between anthropometry and ovarian cancer risk, results have been inconsistent.

METHODS

The associations of height, body mass index (BMI), and ovarian cancer risk were examined in a pooled analysis of primary data from 12 prospective cohort studies from North America and Europe. The study population consisted of 531,583 women among whom 2,036 epithelial ovarian cancer cases were identified. To summarize associations, study-specific relative risks (RR) were estimated using the Cox proportional hazards model and then combined using a random-effects model.

RESULTS

Women with height > or =1.70 m had a pooled multivariate RR of 1.38 [95% confidence interval (95% CI), 1.16-1.65] compared with those with height <1.60 m. For the same comparison, multivariate RRs were 1.79 (95% CI, 1.07-3.00) for premenopausal and 1.25 (95% CI, 1.04-1.49) for postmenopausal ovarian cancer (P(interaction) = 0.14). The multivariate RR for women with a BMI > or =30 kg/m(2) was 1.03 (95% CI, 0.86-1.22) compared with women with a BMI from 18.5 to 23 kg/m(2). For the same comparison, multivariate RRs were 1.72 (95% CI, 1.02-2.89) for premenopausal and 1.07 (95% CI, 0.87-1.33) for postmenopausal women (P(interaction) = 0.07). There was no statistically significant heterogeneity between studies with respect to height or BMI. BMI in early adulthood was not associated with ovarian cancer risk.

CONCLUSION

Height was associated with an increased ovarian cancer risk, especially in premenopausal women. BMI was not associated with ovarian cancer risk in postmenopausal women but was positively associated with risk in premenopausal women.

Caffeine, alcohol, smoking, and the risk of incident epithelial ovarian cancer

BACKGROUND

Smoking, caffeine, and alcohol intake are all potentially modifiable factors that have an unclear association with ovarian cancer risk. Therefore, the associations between these exposures and ovarian cancer risk were prospectively examined among 110,454 women in the Nurses' Health Study (NHS) for the smoking analyses and 80,253 women for the dietary analyses.

METHODS

Women completed biennial questionnaires assessing ovarian cancer risk factors beginning in 1976, with food frequency questionnaires administered every 2 to 4 years starting in 1980. For the smoking analyses, 737 confirmed cases of epithelial ovarian cancer were identified and for the dietary aims, 507 cases were identified through June 1, 2004.

RESULTS

Compared with never-smokers, neither current nor past smoking was associated with ovarian cancer risk overall; however, both were associated with mucinous tumors (n = 69; rate ratio [RR], past = 2.02 [95% confidence interval (CI), 1.15-3.55]; RR, current = 2.22 [95% CI, 1.16-4.24]). A modest inverse association between caffeine intake and ovarian cancer risk was observed (RR, top vs bottom quintile = 0.80; 95% CI, 0.60-1.07 [P = .03]), which was strongest for women who had never used either oral contraceptives (RR = 0.65; 95% CI, 0.46-0.92 [P for heterogeneity = .02]) or postmenopausal hormones (RR = 0.57; 95% CI, 0.36-0.91 [P for heterogeneity = .13]). Alcohol was not associated with ovarian cancer risk.

CONCLUSIONS

The results of the current study suggest that cigarette smoking may only increase the risk for mucinous ovarian tumors, and alcohol intake was not associated with risk. However, an inverse association was observed between caffeine intake and ovarian cancer risk, particularly in women not using hormones; this finding merits further study.

Risk factors for ovarian cancer: an overview with emphasis on hormonal factors

Ovarian cancer is the fifth most frequently occurring cancer among women and leading cause of gynecological cancer deaths in North America. Although the etiology of ovarian cancer is not clear, certain factors are implicated in the etiology of this disease, such as ovulation, gonadotropic and steroid hormones, germ cell depletion, oncogenes and tumor suppressor genes, growth factors, cytokines, and environmental agents. Family history of breast or ovarian cancer is a prominent risk factor for ovarian cancer, with 5-10% of ovarian cancers due to heritable risk. Reproductive factors such as age at menopause and infertility contribute to greater risk of ovarian cancer, whereas pregnancy, tubal ligation, and hysterectomy reduce risk. Oral contraceptive (OC) use has clearly been shown to be protective against ovarian cancer. In contrast, large epidemiologic studies found hormone replacement therapy (HRT) to be a greater risk factor for ovarian cancer. The marked influence of hormones and reproductive factors on ovarian cancer suggests that endocrine disrupters may impact risk; however, there is a notable lack of research in this area. Lifestyle factors such as cigarette smoking, obesity, and diet may affect ovarian cancer risk. Exposure to certain environmental agents such as talc, pesticides, and herbicides may increase risk of ovarian cancer; however, these studies are limited. Further research is needed to strengthen the database of information from which an assessment of environmental and toxicological risk factors for ovarian cancer can be made.

Cigarette smoking and risk of epithelial ovarian cancer

BACKGROUND

An increased risk of mucinous ovarian tumors among cigarette smokers has been observed in multiple studies. The association of smoking with other histologic types of ovarian cancer is less clear, but potentially holds greater importance for prevention of disease incidence and mortality.

METHODS

In a population-based study of 812 women with ovarian cancer diagnosed in western Washington State from 2002-2005 and 1,313 controls, we assessed the risk associated with cigarette smoking, with a particular focus on tumor subgroups jointly classified according to the degree of invasiveness and histology. Information was collected through in-person interviews, and logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

The incidence of both borderline and invasive mucinous ovarian tumors was increased among women with a history of cigarette smoking (ORs and 95% CIs = 1.8, 1.2-2.9, and 1.8, 0.8-4.3, respectively). Increases in risk of these tumor types were most evident among women with greater smoking duration and pack-years of exposure, and among those who had smoked within the prior 15 years. We noted no clear patterns of risk of serous tumors with duration or pack-years of smoking; however, risk of these tumor types was somewhat elevated among women who had smoked within the previous 15 years (for borderline serous tumors, OR and 95% CI = 1.5, 0.9-2.3; for invasive serous tumors, OR and 95% CI = 1.4, 1.1-1.9). The risk of endometrioid, clear cell, and the remaining histologic types of invasive ovarian cancer was not increased among smokers.

CONCLUSION

In the aggregate, evidence is insufficient to determine whether smoking is linked with risk of serous or other non-mucinous histologic types of ovarian cancer. Studies that employ additional histopathologic and molecular techniques to more accurately delineate subsets of tumors may improve our understanding of the impact of smoking on ovarian cancer risk.

Intake of coffee and tea and risk of ovarian cancer: a prospective cohort study

There is some evidence from case-control studies that coffee consumption might be positively associated with ovarian cancer risk, whereas the epidemiologic evidence regarding tea consumption and ovarian cancer is inconsistent. To date, there have been few prospective studies of these associations. Therefore, we examined ovarian cancer risk in association with both coffee and tea intake in a prospective cohort study 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 daily intake of coffee and tea. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association between categories of coffee and tea intake and ovarian cancer risk. During a mean 16.4 years of follow-up, we observed 264 incident ovarian cancer cases. Tea intake was not associated with ovarian cancer risk in our study population. In contrast, a borderline positive association was observed among women who drank > 4 cups coffee/day compared to women who did not drink coffee (HR = 1.62, 95% CI = 0.95-2.75, P(trend) = 0.06). Given the pervasive use of these beverages, the associations between coffee and tea consumption and ovarian cancer risk warrant investigation in further prospective studies.

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.

Dietary folate consumption and risk of ovarian cancer: a prospective cohort study

Deficient dietary folate intake may be associated with increased cancer risk in humans owing to DNA damage resulting from impaired nucleotide excision repair. It is conceivable that an association with folate may be modified by alcohol and/or methionine intake given that alcohol consumption and low methionine intakes both increase dietary folate requirements. In the cohort study reported here, we examined the association between dietary folate intake and ovarian cancer risk, overall and within strata defined by alcohol and methionine intakes. The investigation was conducted in 49 613 Canadian women who were participants in the National Breast Screening Study and who completed self-administered lifestyle and food frequency questionnaires between 1980 and 1985. Linkages to cancer and national mortality databases yielded data on cancer incidence and deaths among cohort members, with follow-up ending between 1998 and 2000. During a mean 16.4 years of follow-up, we observed 264 incident ovarian cancer cases among 48 766 women for whom data were available. Dietary folate intake was associated with a 25% decrease in risk of ovarian cancer for the highest versus the lowest quartile level of intake (hazard ratio=0.75, 95% confidence interval=0.42-1.34, Ptrend=0.25). On stratification by alcohol intake, dietary folate was not associated with ovarian cancer risk among women consuming <4 g/day of alcohol, but there was some suggestion of reduced risk at relatively high levels of folate intake among women consuming > or =4 g/day of alcohol/day (Ptrend=0.09; Pinteraction=0.22). The association between folate and ovarian cancer risk did not vary by strata of methionine intake (Pinteraction=0.98). Our findings, while not statistically significant, suggest that relatively high dietary folate intake may be associated with a reduction in ovarian cancer risk among women with relatively high alcohol consumption and among those with relatively high methionine intake.

The effect of lifestyle factors on gynaecological cancer

Several lifestyle factors affect a woman's risk of gynaecological cancer and-potentially-can be modified to reduce risk. This chapter summarises the evidence for the effect of lifestyle factors on the incidence of gynaecological malignancy. The incidence of obesity is increasing in the developed world such that it now contributes as much as smoking to overall cancer deaths. Women with a body mass index (BMI)>40 have a 60% higher risk of dying from all cancers than women of normal weight. They are also at increased risk from gynaecological cancer. Dietary factors significantly influence the risk of gynaecological cancer: fruit, vegetables and antioxidants reduce risk whereas high animal fat and energy intakes increase risk. Alcohol intake adversely affects breast cancer risk, possibly accounting for 4% of all breast cancers. Physical activity protects against ovarian, endometrial and postmenopausal breast cancer, independently of BMI. The oral contraceptive pill has a substantial and long-lasting effect on the prevention of ovarian and endometrial cancer and is one of the best examples of large-scale chemoprevention in the developed world. Childbearing is protective against ovarian, endometrial and breast cancer but increases the risk of cervical cancer. Smoking acts as a cofactor in cervical carcinogenesis and increases the risk of ovarian cancer, particularly mucinous tumours.

Ovarian cancer

Ovarian cancer accounts for 4% of all cancers in women and is the leading cause of death from gynaecologic malignancies. Because early-stage ovarian cancer is generally asymptomatic, approximately 75% of women present with advanced disease at diagnosis. Survival is highly dependent on stage of disease: 5-year survival in patients with early-stage is 80-90% compared to 25% for patients with advanced-stage disease. For all patients, a comprehensive surgical staging should be performed to obtain the histological confirmation of diagnosis and to evaluate the extent of disease. Patients with early-stage should both be optimally staged and be treated with adjuvant platinum-based chemotherapy if they have a medium or high-risk tumour. For advanced disease the currently recommended management is primary cytoreductive surgery followed by platinum-paclitaxel combination chemotherapy. Appropriate salvage therapy is based on the timing and nature of recurrence and the extent of prior chemotherapy. Surgical resection should be considered in patients with long-term remission, especially in those with isolated recurrences and good performance status. Platinum-based combination represents the standard second-line chemotherapy in patients with platinum-sensitive relapsed ovarian cancer. Salvage chemotherapy in platinum-refractory patients usually results in low response rates and short survival.

Does smoking increase risk of ovarian cancer? A systematic review

OBJECTIVES

Although early reports suggested that smoking was not associated with ovarian cancer risk, recent studies have reported positive associations for cancers of the mucinous subtype. We sought to clarify the relationship between smoking and ovarian cancer by histological subtype.

METHODS

We conducted a systematic literature review and meta-analysis of studies investigating the association between smoking and risk of the different histological subtypes of epithelial ovarian cancer. Eight population-based case-control studies, one pooled analysis of case-control studies, and one cohort study met the inclusion criteria. Summary relative risks (RR), 95% confidence intervals (CI), and tests for heterogeneity were generated from random effects models.

RESULTS

Combined, these studies included a total of 910 women with mucinous and 5564 with non-mucinous ovarian cancers. There was a significant doubling of risk of mucinous ovarian cancer in current smokers compared to never smokers (summary RR 2.1, 95% CI 1.7-2.7), but no increased risk of serous (1.0, 95% CI 0.8-1.2) or endometrioid (0.8, 95% CI 0.6-1.1) cancers and a significant risk reduction for clear cell cancers (0.6, 95% CI 0.3-0.9). The risk of mucinous cancer increased with increasing amount smoked but returned to that of never smokers within 20-30 years of stopping smoking.

CONCLUSIONS

Meta-analysis suggests that current smoking doubles a woman's risk of developing mucinous ovarian cancer. Stopping smoking returns the risk to normal in the long term. Smoking may thus be one of the few modifiable factors offering potential for primary prevention of mucinous ovarian cancer.

Optometrists as key providers in the prevention and early detection of malignancies

Optometrists have become active in many aspects of primary health care. Opportunities exist for optometrists to join other health care providers in the fight against cancer. The purpose of this article is to review information about cancer epidemiology, describe cancer screening guidelines, and to provide examples of ways for optometrists to become involved in promoting goals for reducing cancer risk and increasing the early detection of cancer. In addition to diagnosing ocular cancers and metastases to the eye and orbital region, optometrists may provide cancer information as part of their case history, provide positive health messages to reduce cancer risk factors, and directly observe signs of skin cancer.

Intake of the major carotenoids and the risk of epithelial ovarian cancer in a pooled analysis of 10 cohort studies

Carotenoids, found in fruits and vegetables, have the potential to protect against cancer because of their properties, including their functions as precursors to vitamin A and as antioxidants. We examined the associations between intakes of alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin and lycopene and the risk of invasive epithelial ovarian cancer. The primary data from 10 prospective cohort studies in North America and Europe were analyzed and then pooled. Carotenoid intakes were estimated from a validated food frequency questionnaire administered at baseline in each study. Study-specific relative risks (RR) were estimated using the Cox proportional hazards model and then combined using a random-effects model. Among 521,911 women, 2,012 cases of ovarian cancer occurred during a follow-up of 7-22 years across studies. The major carotenoids were not significantly associated with the risk of ovarian cancer. The pooled multivariate RRs (95% confidence intervals) were 1.00 (0.95-1.05) for a 600 microg/day increase in alpha-carotene intake, 0.96 (0.93-1.03) for a 2,500 microg/day increase in beta-carotene intake, 0.99 (0.97-1.02) for a 100 microg/day increase in beta-cryptoxanthin intake, 0.98 (0.94-1.03) for a 2,500 microg/day increase in lutein/zeaxanthin intake and 1.01 (0.97-1.05) for a 4,000 microg/day increase in lycopene intake. These associations did not appreciably differ by study (p-values, tests for between-studies heterogeneity >0.17). Also, the observed associations did not vary substantially by subgroups of the population or by histological type of ovarian cancer. These results suggest that consumption of the major carotenoids during adulthood does not play a major role in the incidence of ovarian cancer.

In vitro exposure to environmental tobacco smoke induces CYP1B1 expression in human luteinized granulosa cells

Women smokers and women exposed to environmental tobacco smoke (ETS) have reduced ovarian function as evidenced by an earlier menopause, reduced follicular numbers, decreased levels of circulating estradiol, and decreased conception rates; however, the mechanism of action of altered ovarian function by ETS is poorly understood. The direct effects of ETS were evaluated using human luteinized granulosa cells (HLGCs) exposed to ETS in primary cell culture. Exposure to ETS caused a decrease in both estradiol and progesterone production. There was a concentration dependent increase in CYP1B1 gene and protein expression without a change in catechol-O-methyltransferase (COMT) expression. This is the first report of CYP1B1 induction secondary to ETS exposure in cells from the human ovary. CYP1B1 metabolizes both endogenous estrogens and polyaromatic hydrocarbons in ETS to a variety of reactive species and may contribute to the complex effects of ETS on ovarian function.

Alcohol intake and ovarian cancer risk: a pooled analysis of 10 cohort studies

Alcohol has been hypothesized to promote ovarian carcinogenesis by its potential to increase circulating levels of estrogen and other hormones; through its oxidation byproduct, acetaldehyde, which may act as a cocarcinogen; and by depletion of folate and other nutrients. Case–control and cohort studies have reported conflicting results relating alcohol intake to ovarian cancer risk. We conducted a pooled analysis of the primary data from ten prospective cohort studies. The analysis included 529 638 women among whom 2001 incident epithelial ovarian cases were documented. After study-specific relative risks (RR) and 95% confidence intervals (CI) were calculated by Cox proportional hazards models, and then were pooled using a random effects model; no associations were observed for intakes of total alcohol (pooled multivariate RR=1.12, 95% CI 0.86–1.44 comparing ⩾30 to 0 g day⁻¹ of alcohol) or alcohol from wine, beer or spirits and ovarian cancer risk. The association with alcohol consumption was not modified by oral contraceptive use, hormone replacement therapy, parity, menopausal status, folate intake, body mass index, or smoking. Associations for endometrioid, mucinous, and serous ovarian cancer were similar to the overall findings. This pooled analysis does not support an association between moderate alcohol intake and ovarian cancer risk.

Prevention of ovarian cancer

Ovarian cancer is the leading cause of death from gynaecological malignancy. The incidence is high in the Western world. The incidence of ovarian cancer is reduced by pregnancy, lactation, the oral contraceptive pill and tubal ligation. Lifestyle factors are important in the aetiology of ovarian cancer and current evidence suggests the risk can be reduced by eating a diet rich in fruit and vegetables, taking regular exercise, avoiding smoking, avoiding being overweight and avoiding long-term use of hormonal replacement therapy (HRT). Familial ovarian cancer is responsible for about 10% of ovarian cancer cases. Strategies available to high-risk women include screening (covered elsewhere) and prophylactic salpingo-oophorectomy. The precise role of chemoprevention for high-risk women in the form of the oral contraceptive pill is unclear.

A Pooled Analysis of 12 Cohort Studies of Dietary Fat, Cholesterol and Egg Intake and Ovarian Cancer

Fat and cholesterol are theorized to promote ovarian carcinogenesis by increasing circulating estrogen levels. Although case-control studies have reported positive associations between total and saturated fat intake and ovarian cancer risk, two cohort studies have observed null associations. Dietary cholesterol and eggs have been positively associated with ovarian cancer risk. A pooled analysis was conducted on 12 cohort studies. Among 523,217 women, 2,132 incident epithelial ovarian cancer cases were identified. Study-specific relative risks (RR) and 95% confidence intervals (CI) were calculated by Cox proportional hazards models, and then pooled using a random effects model. Total fat intake was not associated with ovarian cancer risk (pooled multivariate RR = 1.08, 95% CI 0.86-1.34 comparing > or =45 to 30-<35% of calories). No association was observed for monounsaturated, polyunsaturated, trans-unsaturated, animal and vegetable fat, cholesterol and egg intakes with ovarian cancer risk. A weakly positive, but non-linear association, was observed for saturated fat intake (pooled multivariate RR = 1.29, 95% CI: 1.01-1.66 comparing highest versus lowest decile). Results for histologic subtypes were similar. Overall, fat, cholesterol and egg intakes were not associated with ovarian cancer risk. The positive association for saturated fat intake at very high intakes merits further investigation.

Cigarette smoking 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. N-nitroso compounds are known carcinogens, which are found in cigarette smoke and can induce gliomas in rats. On this basis, it has been hypothesized that cigarette smoking may be associated with an increased risk of glioma. We investigated the association between cigarette smoking and glioma risk in 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 hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between cigarette smoking and risk of glioma. During a mean of 16.4 years of follow-up, we observed 120 incident glioma cases. Among ever smokers, women who reported having quit smoking had a 51% increase in risk of glioma compared with never smokers (HR = 1.51, 95% CI = 0.97-2.34), while current smokers did not appear to have an increase in risk. When the association with former smokers was further examined by years since quitting, women who had quit smoking >10 years before baseline were at a decreased risk of glioma compared with women who had quit within the 10 years prior to baseline (HR = 0.55, 95% CI = 0.29-1.07), indicating that the association between former smokers and glioma may be driven by women, who recently quit smoking. Compared with nonsmokers, duration of cigarette smoking, number of cigarettes smoked per day and pack-years of smoking were associated with increased glioma risk, although the increases in risk were relatively modest. The present study provides some support for a positive association between cigarette smoking and risk of glioma.

Dairy products and ovarian cancer: a pooled analysis of 12 cohort studies

BACKGROUND

Dairy foods and their constituents (lactose and calcium) have been hypothesized to promote ovarian carcinogenesis. Although case-control studies have reported conflicting results for dairy foods and lactose, several cohort studies have shown positive associations between skim milk, lactose, and ovarian cancer.

METHODS

A pooled analysis of the primary data from 12 prospective cohort studies was conducted. The study population consisted of 553,217 women among whom 2,132 epithelial ovarian cases were identified. Study-specific relative risks and 95% confidence intervals were calculated by Cox proportional hazards models and then pooled by a random-effects model.

RESULTS

No statistically significant associations were observed between intakes of milk, cheese, yogurt, ice cream, and dietary and total calcium intake and risk of ovarian cancer. Higher lactose intakes comparing > or = 30 versus <10 g/d were associated with a statistically significant higher risk of ovarian cancer, although the trend was not statistically significant (pooled multivariate relative risk, 1.19; 95% confidence interval, 1.01-1.40; P(trend) = 0.19). Associations for endometrioid, mucinous, and serous ovarian cancer were similar to the overall findings.

DISCUSSION

Overall, no associations were observed for intakes of specific dairy foods or calcium and ovarian cancer risk. A modest elevation in the risk of ovarian cancer was seen for lactose intake at the level that was equivalent to three or more servings of milk per day. Because a new dietary guideline recommends two to three servings of dairy products per day, the relation between dairy product consumption and ovarian cancer risk at these consumption levels deserves further examination.

Active and passive smoking and risk of ovarian cancer

It is unclear whether smoking is a risk factor for epithelial ovarian cancer, although some studies have suggested that it may be associated with an increased risk of mucinous tumors. This study investigated the effect of smoking and environmental tobacco smoke (ETS) on ovarian cancer risk among 434 women with primary epithelial ovarian, peritoneal, or fallopian cancers and 868 age- and region-matched hospital controls with nonneoplastic conditions. All participants completed a comprehensive epidemiologic questionnaire. Results indicate that decreased risk of ovarian cancer was associated with being a nonsmoker exposed to ETS (adjusted odds ratio [aOR] 0.68, 95% confidence interval [CI] 0.46-0.99), a former smoker (aOR 0.76, 95% CI 0.53-1.10), or a current smoker (aOR 0.53, 95% CI 0.32-0.88). A similar protective effect was noted for smokers with moderate or high exposure based on smoking intensity, duration, and cumulative exposure, as well as for never smokers exposed to ETS. Results did not differ substantially by histologic subtype. Although prevailing theories of ovarian cancer etiology implicate incessant ovulation, characteristics of the study population suggest that anovulation was not the protective mechanism in this study. Immunosuppression by nicotine or upregulation of enzymes that metabolize carcinogens may be responsible for the effects observed.

Endocrine disrupting chemicals: human exposure and health risks

Endocrine disrupting chemicals (EDCs) have been emphasized due to their threats in fertility, intelligence, and survival. For the last decade, many researchers have investigated EDC-health outcome. However, EDC responses in human were not clearly clarified through experimental and epidemiological data. Therefore, considering particular status of EDC endpoints, we suggest that one of the best ways to prevent unknown health risks from EDCs is to perform exposure monitoring or to do surveillance for EDC release into the environment. For this purpose, this review considers exposure status of EDCs, and EDC-related health risks, focusing on the mainly highlighted EDCs, such as dioxins/PCBs, DDT/DDE, bisphenol A, phthalates, alkylphenols, and phytoestrogens. We also reviewed tobacco, a mixed source of EDC-related endocrine disorders.

Oral Contraceptive Use and Risk of Breast Cancer among Women with a Family History of Breast Cancer: a Prospective Cohort Study

Family history of breast cancer is an established risk factor for breast cancer. In addition, there is evidence that oral contraceptive use may be associated with a moderate increase in breast cancer risk. The three cohort studies that have investigated the relationship between oral contraceptive use and breast cancer risk among women with a family history of breast cancer have yielded mixed results, possibly due to the relatively small sample sizes employed and/or differences in the selection of covariates for inclusion in multivariate models. Therefore, we examined the association between oral contraceptive use and breast cancer risk in a large cohort study in Canada. The cohort consisted of the 27,318 women in the Canadian National Breast Screening Study who reported a family history of breast cancer on enrollment into the study. Linkages to national mortality and cancer databases yielded data on deaths and cancer incidence, with follow-up ending between 1998 and 2000, depending upon the province. During a mean of 16.0 years of follow-up, we observed 1707 incident cases of breast cancer among women with any history of breast cancer of which 795 cases occurred among women with a mother, sister, and/or daughter with breast cancer. Among women with any family history of breast cancer, ever use of oral contraceptives was associated with a 12% reduction in risk of breast cancer (95% confidence interval [CI]=0.73-1.07), and there was an inverse trend with increasing duration of use of borderline statistical significance (p(trend)=0.03). Although we also observed a 25% lower risk of breast cancer associated with oral contraceptive use of greater than 84 months versus never use among women with a first degree relative with breast cancer, this finding was not statistically significant (95% CI=0.47-1.19, p(trend)=0.48). Our data raise the possibility that relatively long duration of oral contraceptive use may be inversely associated with risk among women with a family history of breast cancer.

Relationship between body mass index and the risk of ovarian cancer in the Japanese population: Findings from the Japanese Collaborate Cohort (JACC) study

AIM

The incidence of ovarian cancer in Japan has increased since the 1970s. The many studies that have assessed the relationship between body mass index (BMI) and the risk of ovarian cancer have produced contradictory results. Here we investigated this relation using data from the Japan Collaborative Cohort Study for the Evaluation of Cancer Risk, which was initiated in 1988.

METHODS

A self-administered questionnaire on dietary habits and other risk factors for cancer was completed by 36,456 Japanese women. After 7.6 years of follow up, 38 cases of ovarian cancer were available for analysis. Cox proportional-hazards models were used to compute relative risks and to adjust for confounders.

RESULTS

Compared to women with BMI of 18.5-24.9 kg/m2, the relative risk of ovarian cancer was 2.24 (95% CI = 1.10-4.21) for BMI of 25.0-29.9 and 1.78 (95% CI = 0.24-13.34) for BMI of > or = 30 kg/m2. A test for trend revealed that this finding was statistically significant (P = 0.014).

CONCLUSION

The results of this study suggest that being overweight is independently associated with a higher risk of developing ovarian cancer in the Japanese population.

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.

Fruits and Vegetables and Ovarian Cancer Risk in a Pooled Analysis of 12 Cohort Studies

Because fruits and vegetables are rich in bioactive compounds with potential cancer-preventive actions, increased consumption may reduce the risk of ovarian cancer. Evidence on the association between fruit and vegetable intake and ovarian cancer risk has not been consistent. We analyzed and pooled the primary data from 12 prospective studies in North America and Europe. Fruit and vegetable intake was measured at baseline in each study using a validated food-frequency questionnaire. To summarize the association between fruit and vegetable intake and ovarian cancer, study-specific relative risks (RR) were estimated using the Cox proportional hazards model, and then combined using a random-effects model. Among 560,441 women, 2,130 cases of invasive epithelial ovarian cancer occurred during a maximum follow-up of 7 to 22 years across studies. Total fruit intake was not associated with ovarian cancer risk-the pooled multivariate RR for the highest versus the lowest quartile of intake was 1.06 [95% confidence interval (95% CI), 0.92-1.21; P value, test for trend = 0.73; P value, test for between-studies heterogeneity = 0.74]. Similarly, results for total vegetable intake indicated no significant association (pooled multivariate RR, 0.90; 95% CI, 0.78-1.04, for the highest versus the lowest quartile; P value, test for trend = 0.06; P value, test for between-studies heterogeneity = 0.31). Intakes of botanically defined fruit and vegetable groups and individual fruits and vegetables were also not associated with ovarian cancer risk. Associations for total fruits and vegetables were similar for different histologic types. These results suggest that fruit and vegetable consumption in adulthood has no important association with the risk of ovarian cancer.

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.

Hormonal and reproductive factors and pancreatic cancer risk: a prospective cohort study

OBJECTIVES

We examined pancreatic cancer risk in association with hormonal and reproductive factors 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).

METHODS

Linkages to national cancer and mortality databases yielded data on cancer incidence and deaths of all causes, respectively, with follow-up ending between 1998 and 2000. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association between hormonal and reproductive factors and risk of pancreatic cancer.

RESULTS

During a mean of 16.4 years of follow-up, we observed 187 incident pancreatic cancer cases. Compared with women who were premenopausal at baseline, postmenopausal women were at significantly increased risk of pancreatic cancer (odds ratio = 2.44, 95% confidence interval [CI] = 1.45-4.09). Age at first livebirth, parity, age at menarche, use of oral contraceptive, and use of hormone replacement therapy (HRT) were not associated with altered pancreatic cancer risk in our study population. However, among parous women, risk increased with increasing parity.

CONCLUSION

Other than the increased risk among postmenopausal women, the present study provides little support for associations with hormonal factors. Additional prospective data are needed.

Overexpression of dihydrodiol dehydrogenase is associated with cisplatin-based chemotherapy resistance in ovarian cancer patients

OBJECTIVE

Results of a recent study on human ovarian cancer cell lines indicated that overexpression of dihydrodiol dehydrogenase (DDH) was associated with resistance to cisplatin and disease progression. We examined the relationships between DDH expression and chemotherapy resistance in ovarian cancer patients.

METHODS

Using immunohistochemistry, expression of DDH was measured in 41 patients with epithelial ovarian cancers. All patients underwent primary debulking surgery, followed with six cycles of cisplatin-based chemotherapy. Normal ovarian tissues were obtained from patients with benign gynecologic diseases (n = 14). Expression of DDH was confirmed by reverse transcription-polymerase chain reaction. The correlation between DDH expression and clinico-pathological parameters was analyzed by statistical analysis. Difference of progression-free survivals between different groups was compared by a log-rank test.

RESULTS

Eighteen ovarian cancer samples (43.9%) expressed DDH at a moderate to strong level. This marked a significant difference from the negligible expression (1/14, 7.1%) found in the control group (P = 0.02). Of interest, the clear cell adenocarcinoma revealed DDH overexpression (75%) and mucinous adenocarcinoma revealed low DDH expression (16.7%), although DDH expression did not show any significant variation according to different histotypes. DDH overexpression was found in a statistically significantly higher percentage of cisplatin-resistant cases (n = 8/11; 72.7%) than in cisplatin-sensitive cases (n = 9/27; 33.3%) (P = 0.037). Using multivariate analysis, only DDH retained as an independent role in predicting a poor chance of response to cisplatin-based treatment. DDH overexpression cases (median 12 months, 95% confidence interval 4-20) demonstrated a shorter progression-free survival than DDH-negative cases (median 28 months, 95% confidence interval 23-33), but this result did not reach the statistical significance (P = 0.1742). In the advance stage, the DDH-positive group has a shorter PFS as compared with DDH-negative group, and this result closely approaches the statistical significance (P = 0.0669).

CONCLUSIONS

DDH is expressed in a high percentage of primary ovarian tumors and its expression may be associated with cisplatin-based chemotherapy resistance. The possible prognostic role of DDH in ovarian carcinoma deserves further study.

Cigarette smoking and the risk of ovarian cancer in the Japanese population: Findings from the Japanese Collaborate Cohort study

AIM

The many studies into the relation between cigarette smoking and the risk of ovarian cancer have produced inconsistent results. Here we investigated this relation using data from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk, initiated in 1988.

METHODS

A self-administered questionnaire on smoking habits and other risk factors for cancer was completed by 34 639 Japanese women. After 7.6 years of follow up, 39 cases of ovarian cancer were available for analyses. Cox proportional-hazards models were used to compute relative risks (RR) and to adjust for confounders.

RESULTS

Relative to those who had never smoked, the RR of ovarian cancer were 1.63 (95% confidence interval [CI] = 0.21-12.50) for former smokers and 2.27 (95% CI = 0.85-6.08) for current smokers. Among current smokers, the RR were 1.48 (95% CI = 0.20-10.92), 5.56 (95% CI = 1.68-19.06), and 1.86 (95% CI = 0.25-14.30) among women who smoked <10, 10-19, and at least 20 pack-years ([number of cigarettes smoked per day/20] x number of years subject has smoked), respectively, relative to those who had never smoked. A test for trend was statistically significant (P = 0.044).

CONCLUSIONS

These data indicate that cigarette smoking increases the risk of developing ovarian cancer in the Japanese population.

Endogenous Hormones and Ovarian Cancer: Epidemiology and Current Hypotheses

The effect of major epidemiologic risk factors for ovarian cancer has been reviewed in the light of several hormonal hypotheses, including the gonadotropin, androgens, progesterone, estrogens, insulin-like growth factor-I, and insulin hypotheses. The role of inclusion cyst formation and Mullerian epithelium differentiation in the pathology of the disease are also briefly outlined. Although based on limited data, the observed tendency in current evidence suggests possible etiologic roles for elevated androgens and estrogens and decreased progesterone in the pathogenesis of ovarian cancer. A direct effect of gonadotropins cannot be entirely ruled out, but it is plausible that their effect on ovarian cancer risk is mediated by stimulation of ovarian steroidogenesis. Insulin-like growth factor-I also emerges as a hormone that may be directly involved in the pathogenesis of the disease, but thus far only one prospective study has examined this association. Hyperinsulinemia is an unlikely risk factor for ovarian cancer. The observed tendency for an increased risk with androgens from ovarian origin (in premenopausal women), the lack of association with adrenal androgens, and the relatively weak associations observed with obesity, hormonal replacement therapy use, and endogenous hormones after menopause suggest that ovarian synthesis of sex steroids rather than their circulating levels may be etiologically important. More data from prospective studies will be crucial to improve our understanding of the etiologic role of endogenous hormones in the pathogenesis of ovarian cancer. Such data will ultimately provide opportunities for research targeted; at early detection and preventive interventions.

Common risk factors of breast and ovarian cancer: recent view

Clinicians, epidemiologists, and public health specialists tend to examine breast and ovarian cancer separately. Although this seems fairly rational and expected, both malignancies are estrogen related and thus share many risk factors. In this review, we investigate the common familial, reproductive, anthropometric, nutritional, and lifestyle risk factors of breast and ovarian cancer. We believe that the parallel examination of the two cancer types could significantly contribute to an improved prevention of "gynecological cancer" as a whole.