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Globally, ovarian cancer is the eighth most common cancer in women, accounting for an estimated 3.7% of cases and 4.7% of cancer deaths in 2020. Until the early 2000s, age-standardized incidence was highest in northern Europe and North America, but this trend has changed; incidence is now declining in these regions and increasing in parts of eastern Europe and Asia. Ovarian cancer is a very heterogeneous disease and, even among the most common type, namely epithelial ovarian cancer, five major clinically and genetically distinct histotypes exist. Most high-grade serous ovarian carcinomas are now recognized to originate in the fimbrial ends of the fallopian tube. This knowledge has led to more cancers being coded as fallopian tube in origin, which probably explains some of the apparent declines in ovarian cancer incidence, particularly in high-income countries; however, it also suggests that opportunistic salpingectomy offers an important opportunity for prevention. The five histotypes share several reproductive and hormonal risk factors, although differences also exist. In this Review, we summarize the epidemiology of this complex disease, comparing the different histotypes, and consider the potential for prevention. We also discuss how changes in the prevalence of risk and protective factors might have contributed to the observed changes in incidence and what this might mean for incidence in the future.

Low serum 25-hydroxy vitamin D concentration is associated with increased fracture risk. It is uncertain whether vitamin D supplementation reduces fractures, or whether intermittent doses are harmful. We aimed to investigate if supplementing adults living in Australia with monthly doses of 60 000 international units (IU) vitamin D3for 5 years or less altered the rate of fractures.

Evidence suggests that vitamin D influences the immune system. Recent studies indicate that vitamin D supplementation may reduce the severity of infections, but this has not been confirmed.

Background Previous studies that showed an association between smoking and adenocarcinomas of the esophagus and esophagogastric junction were limited in their ability to assess differences by tumor site, sex, dose-response, and duration of cigarette smoking cessation. Methods We used primary data from 10 population-based case-control studies and two cohort studies from the Barrett's Esophagus and Esophageal Adenocarcinoma Consortium. Analyses were restricted to white non-Hispanic men and women. Patients were classified as having esophageal adenocarcinoma (n = 1540), esophagogastric junctional adenocarcinoma (n = 1450), or a combination of both (all adenocarcinoma; n = 2990). Control subjects (n = 9453) were population based. Associations between pack-years of cigarette smoking and risks of adenocarcinomas were assessed, as well as their potential modification by sex and duration of smoking cessation. Study-specific odds ratios (ORs) estimated using multivariable logistic regression models, adjusted for age, sex, body mass index, education, and gastroesophageal reflux, were pooled using a meta-analytic methodology to generate summary odds ratios. All statistical tests were two-sided. Results The summary odds ratios demonstrated strong associations between cigarette smoking and esophageal adenocarcinoma (OR = 1.96, 95% confidence interval [CI] -- 1.64 to 2.34), esophagogastric junctional adenocarcinoma (OR = 2.18, 95% CI = 1.84 to 2.58), and all adenocarcinoma (OR = 2.08, 95% CI = 1.83 to 2.37). In addition, there was a strong dose-response association between pack-years of cigarette smoking and each outcome (P < .001). Compared with current smokers, longer smoking cessation was associated with a decreased risk of all adenocarcinoma after adjusting for pack-years ( Conclusions Cigarette smoking is associated with increased risks of adenocarcinomas of the esophagus and esophagogastric junction in white men and women; compared with current smoking, smoking cessation was associated with reduced risks. DOI: 10.1093/jnci/djq289

Background: Variation in meat and fish intakes has been associated with a risk of some cancers, but evidence for ovarian cancer is limited and inconsistent. Objective: We examined the association between intakes of total meat, red meat, processed meat, poultry, and fish and ovarian cancer risk. Design: Data came from 2 Australian population-based case-control studies conducted 10 y apart. Analyses included a total of 2049 cases and 2191 control subjects. We obtained dietary information via a food-frequency questionnaire. We estimated multivariable-adjusted odds ratios (ORs) for each study by using logistic regression and combined results of the 2 studies by using random-effects models. We also assembled the published evidence in a systematic review and meta-analysis. Results: Although there was no association between total or red meat intake and ovarian cancer risk, women with the highest intake of processed meat had a significantly increased risk of ovarian cancer in the 2 case-control studies (combined OR: 1.18; 95% CI: 1.15, 1.21) and the meta-analysis [7 studies; pooled relative risk (RR): 1.20; 95% CI: 1.07, 1.34]. In contrast, a frequent intake of poultry was associated with borderline significant reductions in risk in the 2 case-control studies (combined OR: 0.83; 95% CI: 0.67, 1.03) and the meta-analysis including 7 additional studies (pooled RR: 0.90; 95% CI: 0.79, 1.01). High fish intake was associated with a significantly reduced risk in the 2 case-control studies (combined OR: 0.76; 95% CI: 0.62, 0.94) and a smaller borderline significant reduction in the meta-analysis (6 additional studies; pooled RR: 0.84; 95% CI: 0.68, 1.03). Conclusion: Our results suggest that low consumption of processed meat and higher consumption of poultry and fish may reduce the risk of ovarian cancer. doi: 10.3945/ajcn.2009.28415.

Background: Evidence for a role of individual foods and nutrients in the causation of ovarian cancer is inconclusive. To date, few studies have considered dietary patterns in relation to ovarian cancer risk. Objective: We conducted a population-based case-control study in Australia to identify and analyze dietary patterns in relation to ovarian cancer risk. Design: Principal components analysis of 40 food groups was performed to identify eating patterns in 683 women with epithelial ovarian cancer and in 777 control women aged 18-79 y. Detailed information on risk factors was obtained through face-to-face interviews, whereas dietary information was obtained by administering a semiquantitative food-frequency questionnaire for subjects to complete themselves. Multivariable-adjusted odds ratios (ORs) for ovarian cancer risk were estimated with logistic regression modeling. Results: Three major eating patterns were identified: 'snacks and alcohol,' 'fruit and vegetable,' and 'meat and fat.' A significant inverse association between the snacks and alcohol pattern and ovarian cancer risk (highest compared with lowest group, multivariable-adjusted OR: 0.59; 95% CI: 0.43, 0.82; P for trend: 0.001) was attenuated after further adjustment for white or red wine intake. The fruit and vegetable pattern was not associated with risk. The meat and fat pattern was associated with an increased risk of ovarian cancer (highest compared with lowest group, multivariable-adjusted OR: 2.49; 95% CI: 1.75, 3.55; P for trend < 0.0001). Further adjustment for body mass index strengthened this association. Conclusions: A diet characterized by high meat and fat intake may increase the risk of epithelial ovarian cancer. A diet high in fruit and vegetables was not associated with reduced risk.

Polygenic risk scores (PRS) for epithelial ovarian cancer (EOC) have the potential to improve risk stratification. Joint estimation of Single Nucleotide Polymorphism (SNP) effects in models could improve predictive performance over standard approaches of PRS construction. Here, we implemented computationally efficient, penalized, logistic regression models (lasso, elastic net, stepwise) to individual level genotype data and a Bayesian framework with continuous shrinkage, “select and shrink for summary statistics” (S4), to summary level data for epithelial non-mucinous ovarian cancer risk prediction. We developed the models in a dataset consisting of 23,564 non-mucinous EOC cases and 40,138 controls participating in the Ovarian Cancer Association Consortium (OCAC) and validated the best models in three populations of different ancestries: prospective data from 198,101 women of European ancestries; 7,669 women of East Asian ancestries; 1,072 women of African ancestries, and in 18,915 BRCA1and 12,337 BRCA2pathogenic variant carriers of European ancestries. In the external validation data, the model with the strongest association for non-mucinous EOC risk derived from the OCAC model development data was the S4 model (27,240 SNPs) with odds ratios (OR) of 1.38 (95% CI: 1.28–1.48, AUC: 0.588) per unit standard deviation, in women of European ancestries; 1.14 (95% CI: 1.08–1.19, AUC: 0.538) in women of East Asian ancestries; 1.38 (95% CI: 1.21–1.58, AUC: 0.593) in women of African ancestries; hazard ratios of 1.36 (95% CI: 1.29–1.43, AUC: 0.592) in BRCA1pathogenic variant carriers and 1.49 (95% CI: 1.35–1.64, AUC: 0.624) in BRCA2pathogenic variant carriers. Incorporation of the S4 PRS in risk prediction models for ovarian cancer may have clinical utility in ovarian cancer prevention programs.

The effect of supplementing unscreened adults with vitamin D3on mortality is unclear. We aimed to determine whether monthly doses of vitamin D3influenced mortality in older Australians.

Observational studies have linked vitamin D deficiency with acute respiratory tract infection, but results from randomised controlled trials are heterogeneous. We analysed data from the D-Health Trial to determine whether supplementing older Australian adults, recruited from the general population, with monthly doses of vitamin D reduced the risk, duration, and severity of acute respiratory tract infections.

PurposeThe known epithelial ovarian cancer (EOC) susceptibility genes account for less than 50% of the heritable risk of ovarian cancer suggesting that other susceptibility genes exist. The aim of this study was to evaluate the contribution to ovarian cancer susceptibility of rare deleterious germline variants in a set of candidate genes.MethodsWe sequenced the coding region of 54 candidate genes in 6385 invasive EOC cases and 6115 controls of broad European ancestry. Genes with an increased frequency of putative deleterious variants in cases versus controls were further examined in an independent set of 14 135 EOC cases and 28 655 controls from the Ovarian Cancer Association Consortium and the UK Biobank. For each gene, we estimated the EOC risks and evaluated associations between germline variant status and clinical characteristics.ResultsThe ORs associated for high-grade serous ovarian cancer were 3.01 for PALB2(95% CI 1.59 to 5.68; p=0.00068), 1.99 for POLK(95% CI 1.15 to 3.43; p=0.014) and 4.07 for SLX4(95% CI 1.34 to 12.4; p=0.013). Deleterious mutations in FBXO10were associated with a reduced risk of disease (OR 0.27, 95% CI 0.07 to 1.00, p=0.049). However, based on the Bayes false discovery probability, only the association for PALB2in high-grade serous ovarian cancer is likely to represent a true positive.ConclusionsWe have found strong evidence that carriers of PALB2deleterious mutations are at increased risk of high-grade serous ovarian cancer. Whether the magnitude of risk is sufficiently high to warrant the inclusion of PALB2in cancer gene panels for ovarian cancer risk testing is unclear; much larger sample sizes will be needed to provide sufficiently precise estimates for clinical counselling.

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ABSTRACTObservational studies suggest a link between vitamin D and the composition of the gut microbiome, but there is little evidence from randomized controlled trials of vitamin D supplementation. We analyzed data from the D-Health Trial, a randomized, double-blind, placebo-controlled trial. We recruited 21,315 Australians aged 60–84 y and randomized them to 60,000 IU of vitamin D3or placebo monthly for 5 y. Stool samples were collected from a sample of 835 participants (417 in the placebo and 418 in the vitamin D group) approximately 5 y after randomization. We characterized the gut microbiome using 16S rRNA gene sequencing. We used linear regression to compare alpha diversity indices (i.e. Shannon index (primary outcome), richness, inverse Simpson index), and the ratio of Firmicutes to Bacteroidetes between the two groups. We analyzed between-sample (beta) diversity (i.e. Bray Curtis distance and UniFrac index) using principal coordinate analysis and used PERMANOVA to test for significant clustering according to randomization group. We also assessed the difference in the abundance of the 20 most abundant genera between the two groups using negative binomial regression model with adjustment for multiple testing. Approximately half the participants included in this analysis were women (mean age 69.4 y). Vitamin D supplementation did not alter the Shannon diversity index (mean 3.51 versus 3.52 in the placebo and vitamin D groups, respectively, p = 0.50). Similarly, there was little difference between the groups for other alpha diversity indices, the abundance of different genera, and the Firmicutes-to-Bacteroidetes ratio. We did not observe clustering of bacterial communities according to randomization group. In conlusion, monthly doses of 60,000 IU of vitamin D supplementation for 5 y did not alter the composition of the gut microbiome in older Australians.

(Abstracted from J Clin Oncol2022; doi: 10.1200/JCO.21.01900)Ovarian cancer is the deadliest gynecologic cancer because of its nonspecific symptom presentation and lack of early detection or prevention strategies. Chronic inflammation has been demonstrated to play a key role in the molecular mechanisms driving ovarian cancer.

Globally, ovarian cancer is the seventh most common cancer in women and the eighth most common cause of cancer death, with five-year survival rates below 45%. Although age-standardised rates are stable or falling in most high-income countries, they are rising in many low and middle income countries. Furthermore, with increasing life-expectancy, the number of cases diagnosed each year is increasing. To control ovarian cancer we need to understand the causes. This will allow better prediction of those at greatest risk for whom screening might be appropriate, while identification of potentially modifable causes provides an opportunity for intervention to reduce rates. In this paper we will summarise the current state of knowledge regarding the known and possible causes of epithelial ovarian cancer and discuss some of the main theories of ovarian carcinogenesis. We will also briefly review the relationship between lifestyle and survival after a diagnosis of ovarian cancer.

To identify common alleles associated with different histotypes of epithelial ovarian cancer (EOC), we pooled data from multiple genome-wide genotyping projects totaling 25,509 EOC cases and 40,941 controls. We identified nine new susceptibility loci for different EOC histotypes: six for serous EOC histotypes (3q28, 4q32.3, 8q21.11, 10q24.33, 18q11.2 and 22q12.1), two for mucinous EOC (3q22.3 and 9q31.1) and one for endometrioid EOC (5q12.3). We then performed meta-analysis on the results for high-grade serous ovarian cancer with the results from analysis of 31,448 BRCA1 and BRCA2 mutation carriers, including 3,887 mutation carriers with EOC. This identified three additional susceptibility loci at 2q13, 8q24.1 and 12q24.31. Integrated analyses of genes and regulatory biofeatures at each locus predicted candidate susceptibility genes, including OBFC1, a new candidate susceptibility gene for low-grade and borderline serous EOC.

Malnutrition is common during treatment for ovarian cancer and one in three report multiple symptoms affecting food intake after primary treatment. Little is known about diet post-treatment in relation to ovarian cancer survival, however, general recommendations for cancer survivors are to maintain a higher level of protein intake to support recovery and minimize nutritional deficits.

ObjectiveTo investigate whether supplementing older adults with monthly doses of vitamin D alters the incidence of major cardiovascular events.DesignRandomised, double blind, placebo controlled trial of monthly vitamin D (the D-Health Trial). Computer generated permuted block randomisation was used to allocate treatments.SettingAustralia from 2014 to 2020.Participants21 315 participants aged 60-84 years at enrolment. Exclusion criteria were self-reported hypercalcaemia, hyperparathyroidism, kidney stones, osteomalacia, sarcoidosis, taking >500 IU/day supplemental vitamin D, or unable to give consent because of language or cognitive impairment.Intervention60 000 IU/month vitamin D3(n=10 662) or placebo (n=10 653) taken orally for up to five years. 16 882 participants completed the intervention period: placebo 8270 (77.6%); vitamin D 8552 (80.2%).Main outcome measuresThe main outcome for this analysis was the occurrence of a major cardiovascular event, including myocardial infarction, stroke, and coronary revascularisation, determined through linkage with administrative datasets. Each event was analysed separately as secondary outcomes. Flexible parametric survival models were used to estimate hazard ratios and 95% confidence intervals.Results21 302 people were included in the analysis. The median intervention period was five years. 1336 participants experienced a major cardiovascular event (placebo 699 (6.6%); vitamin D 637 (6.0%)). The rate of major cardiovascular events was lower in the vitamin D group than in the placebo group (hazard ratio 0.91, 95% confidence interval 0.81 to 1.01), especially among those who were taking cardiovascular drugs at baseline (0.84, 0.74 to 0.97; P for interaction=0.12), although the P value for interaction was not significant (<0.05). Overall, the difference in standardised cause specific cumulative incidence at five years was −5.8 events per 1000 participants (95% confidence interval −12.2 to 0.5 per 1000 participants), resulting in a number needed to treat to avoid one major cardiovascular event of 172. The rate of myocardial infarction (hazard ratio 0.81, 95% confidence interval 0.67 to 0.98) and coronary revascularisation (0.89, 0.78 to 1.01) was lower in the vitamin D group, but there was no difference in the rate of stroke (0.99, 0.80 to 1.23).ConclusionsVitamin D supplementation might reduce the incidence of major cardiovascular events, although the absolute risk difference was small and the confidence interval was consistent with a null finding. These findings could prompt further evaluation of the role of vitamin D supplementation, particularly in people taking drugs for prevention or treatment of cardiovascular disease.Trial registrationACTRN12613000743763

Basal cell and squamous cell carcinomas of the skin are the commonest cancers in humans, yet no validated tools exist to estimate future risks of developing keratinocyte carcinomas. To develop a prediction tool, we used baseline data from a prospective cohort study (n = 38,726) in Queensland, Australia, and used data linkage to capture all surgically excised keratinocyte carcinomas arising within the cohort. Predictive factors were identified through stepwise logistic regression models. In secondary analyses, we derived separate models within strata of prior skin cancer history, age, and sex. The primary model included terms for 10 items. Factors with the strongest effects were >20 prior skin cancers excised (odds ratio 8.57, 95% confidence interval [95% CI] 6.73–10.91), >50 skin lesions destroyed (odds ratio 3.37, 95% CI 2.85–3.99), age ≥ 70 years (odds ratio 3.47, 95% CI 2.53–4.77), and fair skin color (odds ratio 1.75, 95% CI 1.42–2.15). Discrimination in the validation dataset was high (area under the receiver operator characteristic curve 0.80, 95% CI 0.79–0.81) and the model appeared well calibrated. Among those reporting no prior history of skin cancer, a similar model with 10 factors predicted keratinocyte carcinoma events with reasonable discrimination (area under the receiver operator characteristic curve 0.72, 95% CI 0.70–0.75). Algorithms using self-reported patient data have high accuracy for predicting risks of keratinocyte carcinomas.

We conducted a meta-analysis of three endometrial cancer genome-wide association studies (GWAS) and two follow-up phases totaling 7,737 endometrial cancer cases and 37,144 controls of European ancestry. Genome-wide imputation and meta-analysis identified five new risk loci of genome-wide significance at likely regulatory regions on chromosomes 13q22.1 (rs11841589, near KLF5), 6q22.31 (rs13328298, in LOC643623 and near HEY2 and NCOA7), 8q24.21 (rs4733613, telomeric to MYC), 15q15.1 (rs937213, in EIF2AK4, near BMF) and 14q32.33 (rs2498796, in AKT1, near SIVA1). We also found a second independent 8q24.21 signal (rs17232730). Functional studies of the 13q22.1 locus showed that rs9600103 (pairwise r2= 0.98 with rs11841589) is located in a region of active chromatin that interacts with the KLF5 promoter region. The rs9600103[T] allele that is protective in endometrial cancer suppressed gene expression in vitro, suggesting that regulation of the expression of KLF5, a gene linked to uterine development, is implicated in tumorigenesis. These findings provide enhanced insight into the genetic and biological basis of endometrial cancer.

Objective:To estimate the numbers and proportions of cancers occurring in Australia in 2010 attributable to modifiable causal factors. Methods:We estimated the population attributable fraction (PAF) of cancers associated with exposure to 13 causal factors using standard formulae incorporating exposure prevalence and relative risk data. We also calculated the potential impact of changing exposure to some factors. Results:A total of 32% of all cancers diagnosed in Australia in 2010 (excluding keratinocyte cancers) were attributable to the 13 factors assessed (men 33%; women 31%). Leading factors were tobacco smoke (PAF all cancers: 13.4%), solar radiation (6.2%), inadequate diet (6.1%) and overweight/obesity (3.4%). Factors conferring highest PAFs differed by sex: highest PAFs for men were tobacco smoke (15.8%), solar radiation (7.1%) and alcohol (3.0%); while highest PAFs for women were tobacco smoke (10.1%), solar radiation (5.0%) and overweight/obesity (4.5%). Sites with the highest counts of potentially preventable cancers were lung (8,569), colorectal (7,404), melanoma of the skin (7,220) and breast (3,233). Conclusions:At least one in three cancers in Australia is attributable to exposure to known modifiable factors. Implications:Up to 37,000 cancers could be prevented in Australia each year if the population avoided exposure to 13 common factors known or strongly suspected to cause cancer.

Objectives:To estimate the proportion and numbers of cancers occurring in Australia in 2010 attributable to insufficient levels of physical activity. Methods:We estimated the population attributable fraction (PAF) of cancers causally associated with insufficient physical activity (colon, post‐menopausal breast and endometrium) using standard formulae incorporating prevalence of insufficient physical activity (<60 minutes at least 5 days/week), relative risks associated with physical activity and cancer incidence. We also estimated the proportion change in cancer incidence (potential impact fraction [PIF]) that may have occurred assuming that everyone with insufficient activity levels increased their exercise by 30 minutes/week. Results:An estimated 1,814 cases of colon, post‐menopausal breast and endometrial cancer were attributable to insufficient levels of physical activity: 707 (6.5%) colon; 971 (7.8%) post‐menopausal breast; and 136 (6.0%) endometrial cancers. If those exercising below the recommended level had increased their activity level by 30 minutes/week, we estimate 314 fewer cancers (17% of those attributable to insufficient physical activity) would have occurred in 2010. Conclusions:More than 1,500 cancers were attributable to insufficient levels of physical activity in the Australian population. Implications:Increasing the proportion of Australians who exercise could reduce the incidence of several common cancers.

Objective:To describe the approach underpinning a national project to estimate the numbers and proportions of cancers occurring in Australia in 2010 that are attributable to modifiable causal factors. Methods:We estimated the population attributable fraction (PAF) (or prevented fraction) of cancers associated with exposure to causal (or preventive) factors using standard formulae. Where possible, we also estimated the potential impact on cancer incidence resulting from changes in prevalence of exposure. Analyses were restricted to factors declared causal by international agencies: tobacco smoke; alcohol; solar radiation; infectious agents; obesity; insufficient physical activity; insufficient intakes of fruits, vegetables and fibre; red and processed meat; menopausal hormone therapy (MHT); oral contraceptive pill (OCP); and insufficient breast feeding. Separately, we estimated numbers of cancers prevented by: aspirin; sunscreen; MHT; and OCP use. We discuss assumptions pertaining to latent periods between exposure and cancer onset, choices of prevalence data and risk estimates, and approaches to sensitivity analyses. Results:Numbers and population attributable fractions of cancer are presented in accompanying papers. Conclusions:This is the first systematic assessment of population attributable fractions of cancer in Australia.

Objectives:To estimate the proportion and number of cancers occurring in Australia in 2010 attributable to overweight/obesity. Methods:We estimated the population attributable fraction (PAF) and number of cancers causally associated with overweight/obesity. We used standard formulae incorporating Australian prevalence data for body mass index (BMI), relative risks associated with BMI and cancer. We also estimated the proportion change in cancer incidence (potential impact fraction [PIF]) that may have occurred assuming that the prevalence of overweight/obesity had remained at 1990 levels. Results:An estimated 3,917 cancer cases (3.4% of all cancers) diagnosed in 2010 were attributable to overweight/obesity, including 1,101 colon cancers, 971 female post‐menopausal breast cancers and 595 endometrial cancers (PAFs of 10%, 8% and 26%, respectively). Highest PAFs were observed for oesophageal adenocarcinoma (31%), endometrial cancer (26%) and kidney cancer (19%). If the prevalence of overweight/obesity in Australia had remained at levels prevailing in 1990, we estimate there would have been 820 fewer cancers diagnosed in 2010 (PIF 2%). Conclusions:Overweight/obesity causes a substantial number of cancers in Australia. Implications:Public health strategies to reduce the prevalence of overweight and obesity will reduce the incidence of cancer, particularly of the colon, breast and endometrium.

Objectives:To estimate the proportion and number of cancers occurring in Australia in 2010 attributable to parous women having breastfed for total durations of ≤12 months. Methods:We estimated the population attributable fraction (PAF) of breast cancers (the only cancer site with convincing evidence of causal association) associated with women breastfeeding for ≤12 months in total, using standard formulae incorporating breastfeeding prevalence data, relative risks associated with breastfeeding and cancer incidence. We also estimated the proportion change in disease incidence (potential impact fraction [PIF]) that might have occurred under two hypothetical scenarios of women breastfeeding for longer durations. Results:An estimated 235 (1.7%) breast cancer cases that occurred in Australian in 2010 could be attributed to women breastfeeding for total durations of ≤12 months. Assuming a hypothetical increase in breastfeeding, we estimated that the number of breast cancers prevented would range from 36 to 51 (prevented fraction = 0.3% to 0.4%). Conclusions:More than 200 breast cancers were attributable to women breastfeeding for total durations of ≤12 months. Implications:Policies to increase breastfeeding duration may help prevent breast cancers in the future.

Objective:To estimate the proportion and numbers of cancers occurring in Australia in 2010 that are attributable to alcohol consumption. Methods:We estimated the population attributable fraction (PAF) of cancers causally associated with alcohol consumption using standard formulae incorporating prevalence of alcohol consumption and relative risks associated with consumption and cancer. We also estimated the proportion change in cancer incidence (potential impact fraction [PIF]) that might have occurred under the hypothetical scenario that an intervention reduced alcohol consumption, so that no‐one drank >2 drinks/day. Results:An estimated 3,208 cancers (2.8% of all cancers) occurring in Australian adults in 2010 could be attributed to alcohol consumption. The greatest numbers were for cancers of the colon (868) and female breast cancer (830). The highest PAFs were for squamous cell carcinomas of the oral cavity/pharynx (31%) and oesophagus (25%). The incidence of alcohol‐associated cancer types could have been reduced by 1,442 cases (4.3%) – from 33,537 to 32,083 – if no Australian adult consumed >2 drinks/day. Conclusions:More than 3,000 cancers were attributable to alcohol consumption and thus were potentially preventable. Implications:Strategies that limit alcohol consumption to guideline levels could prevent a large number of cancers in Australian adults.

Objectives:To estimate the proportion and number of cancers occurring in Australia in 2010 attributable to menopausal hormone therapy (MHT) use. Methods:We estimated the population attributable fraction for cancers causally associated with MHT (breast, endometrium, ovary), and the proportion of colorectal cancers prevented by MHT. We used standard formulae incorporating Australian prevalence data, relative risks of cancer associated with MHT and cancer incidence. We also estimated potential change in cancer incidence under two hypothetical scenarios whereby 25% fewer Australian women used MHT, or women exclusively used oestrogen‐only MHT. Results:An estimated 539 cancers in Australia in 2010 were attributable to MHT: 453 breast, 67 endometrial and 19 ovarian cancers equating to 3.4%, 3.1% and 1.6% of each cancer type, respectively. In contrast, MHT may have prevented 52 colorectal cancers. If 25% fewer women used MHT, then 141 cancers may have been avoided. If women exclusively used oestrogen‐only MHT then 240 cancers may have been avoided. Conclusions:MHT use caused more than 500 cancers in Australian women in 2010 and prevented ∼50 colorectal cancers. Implications:MHT use continues to cause an excess of cancers. The risks, benefits, regimen and treatment duration should be carefully considered for each woman before MHT is commenced.

Objectives:To estimate the proportion and numbers of cancers in Australia in 2010 attributable to consuming red/processed meat. Methods:We estimated the population attributable fraction (PAF) for cancers causally associated with red/processed meat consumption (colon, rectum) using standard formulae incorporating prevalence of consumption (1995 National Nutrition Survey), relative risks associated with consumption and cancer incidence. We also estimated the proportion change in cancer incidence (potential impact fraction [PIF]) that might have occurred under two hypothetical interventions whereby Australian adults reduced their consumption of red/processed meat from prevailing levels to ≤100 g or ≤65 g per day, respectively. Results:An estimated 2,614 cases (18%) of colorectal cancer occurring in Australians in 2010 were attributable to red/processed meat consumption (16% of colon cancers; 23% of rectal cancers). We estimated that if all Australian adults had consumed ≤65 g/day or ≤100 g/day of red/processed meat, then the incidence of colorectal cancer would have been 5.4% (798 cancers) or 1.4% (204 cancers) lower, respectively. Conclusions:About one in six colorectal cancers in Australians in 2010 were attributable to red/processed meat consumption. Implications:Reducing red/processed meat intake may reduce colorectal cancer incidence, but must be balanced against nutritional benefits of modest lean meat consumption.

Objectives:To estimate the number and proportion of cancers occurring in Australia in 2010 attributable to consumption deficits in fruit, non‐starchy vegetables and dietary fibre. Methods:We estimated the population attributable fraction (PAF) for cancers causally associated with inadequate intake of fruit and non‐starchy vegetables (oral cavity, pharynx, oesophageal squamous cell carcinoma, stomach, larynx); inadequate intake of fruit (lung); and insufficient intake of fibre (colorectum). We used standard formulae incorporating prevalence of exposure (1995 National Nutrition Survey) and relative risks from independent studies. Results:Overall, 1,555 (1.4% of all) and 311 (0.3% of all) cancers were attributable to inadequate intakes of fruit and non‐starchy vegetables, respectively. A further 2,609 colorectal cancers (18% of colorectal) were attributable to insufficient fibre intake. If Australians increased their fibre intake by eating the recommended daily intakes of fruit and vegetables, an estimated 1,293 (8.8%) colorectal cancers could be prevented. Conclusions:One in six colorectal cancer cases was attributable to inadequate intake of dietary fibre and about 1,800 cancers at other sites were attributable to insufficient fruit and non‐starchy vegetable consumption. Implications:Increasing the proportion of Australians who consume the recommended intake of fruit, vegetables and fibre could prevent up to 4% of all cancers.

Objectives:To estimate the population attributable fraction (PAF) and numbers of cancers occurring in Australia in 2010 attributable to tobacco smoking, both personal and by a partner. Methods:We used a modified Peto‐Lopez approach to calculate the difference between the number of lung cancer cases observed and the number expected assuming the entire population developed lung cancer at the same rate as never smokers. For cancers other than lung, we applied the standard PAF formula using relative risks from a large cohort and derived notional smoking prevalence. To estimate the PAF for partners' smoking, we used the standard formula incorporating the proportion of non‐smoking Australians living with an ever‐smoking partner and relative risks associated with partner smoking. Results:An estimated 15,525 (13%) cancers in Australia in 2010 were attributable to tobacco smoke, including 8,324 (81%) lung, 1,973 (59%) oral cavity and pharynx, 855 (60%) oesophagus and 951 (6%) colorectal cancers. Of these, 136 lung cancers in non‐smokers were attributable to partner tobacco smoke. Conclusions:More than one in eight cancers in Australia is attributable to tobacco smoking and would be avoided if nobody smoked. Implications:Strategies to reduce the prevalence of smoking remain a high priority for cancer control.

Objectives:To estimate the proportion and number of cancers occurring in Australia in 2010 attributable to combined oral contraceptive pill (OCP) use. Methods:We estimated the population attributable fraction (PAF) for cancers causally associated with combined OCP use (breast, cervix), and the proportion of endometrial and ovarian cancers prevented (prevented fraction [PF]). We used standard formulae incorporating prevalence of combined OCP use in the Australian population, relative risks of cancer associated with this exposure and cancer incidence. Results:An estimated 105 breast and 52 cervical cancers (0.7% and 6.4% of each cancer, respectively) in Australia in 2010 were attributable to current use of combined OCP. Past combined OCP use was estimated to have prevented 1,032 endometrial and 308 ovarian cancers in 2010, reducing the number of cancers that would otherwise have occurred by 31% and 19%, respectively. Conclusions:A small proportion of breast and cervical cancers is attributable to combined OCP use; OCP use is likely to have prevented larger numbers of endometrial and ovarian cancers. Implications:Women seeking contraceptive advice should be told of potential adverse effects, but should also be told that – along with reproductive health benefits – combined OCP use can reduce long‐term risks of ovarian and endometrial cancers.

Few studies have examined the long-term changes experienced by women treated for endometrial cancer.

(Abstracted from Cancer Epidemiol Biomarkers Prev2016;25(7):1114–1124)It is estimated that 5% of women in the United States and 10% to 50% of women worldwide are physically inactive. Previous studies have demonstrated that recreational physical activity is associated with decreased risks of developing breast, colon, and endometrial cancers.

Objective:Participation rates have been declining in case‐control studies, particularly among controls, raising concerns about possible bias. Formal assessments of the effect of low participation on odds ratios (OR) are seldom presented however. We sought to quantify possible bias using multiple imputation techniques. Methods:Using data from two Australian case‐control studies, we estimated the relative risks of oesophageal squamous cell carcinoma (OSCC) and adenocarcinoma (OAC), and serous ovarian cancer (SOC) associated with smoking and body mass index (BMI). We compared ORs observed using self‐reported data from participating controls with ORs derived using imputed exposures for non‐participating controls. Results:Participating controls were less likely than non‐participants to smoke currently. Smoking remained significantly associated with oesophageal cancer even under the most extreme assumption of smoking prevalence among non‐participants (OSCC: observed OR 6.54, 4.62‐9.28, imputed OR 3.94, 2.83‐5.49; OAC: observed OR 2.69, 1.87‐3.85 imputed OR 1.58, 1.13‐2.22). For SOC however, risks associated with smoking were attenuated to null under plausible smoking assumptions among non‐participants. BMI distributions were similar among participating and non‐participating controls, and risk estimates were essentially unchanged. Conclusion and implications:Bias is not an inevitable consequence of low control participation and depends on the association examined. Sensitivity analyses can assist in interpretation of results.

ABSTRACTHelicobacter pyloriinfection is common among adults with intellectual disability. The acceptabilities and accuracies of different diagnostic tests in this population are unknown. We aimed to determine (i) patient acceptability and (ii) performance characteristics of serology, fecal-antigen, and urea breath tests among adults with intellectual disability. One hundred sixty-eight such adults underwent H. pyloritesting with serology and fecal-antigen tests, and a portion underwent treatment. One year later, the participants were retested with fecal-antigen, serology, and urea breath tests. The numbers of specimens obtained and difficulties in collection reported by caregivers were noted. Test performance characteristics were assessed among participants and 65 of their caregivers, using serology as the reference. All participants provided at least one specimen, despite reported collection difficulties for 23% of fecal and 27% of blood specimens. Only 25% of the participants provided breath specimens; failure to perform this test was associated with lower intellectual ability and higher maladaptive behavior. The sensitivity, specificity, and positive and negative predictive values of the fecal test (baseline and 12 months versus caregivers) were 70 and 63 versus 81, 93 and 95 versus 98, 96 and 92 versus 93, and 53 and 74 versus 93%, respectively; those of the urea breath test (12 months versus caregivers) were 86 versus 100, 88 versus 95, 75 versus 89, and 94 versus 100%, respectively. With assistance, fecal or blood specimens for H. pyloriassessment can be provided by most patients with intellectual disability regardless of their level of function or behavior. Only those with greater ability can perform the urea breath test. Using serology as the reference test, the limitations of performance characteristics of the fecal-antigen and urea breath tests are similar to those among a control group of caregivers.

Incessant ovulation is thought to be one of the primary causes of epithelial ovarian cancer. However, the effects of ovulation at different ages and of the various exposures or events that suppress ovulation have not been established. We used data from an Australian case-control study of 791 ovarian cancer cases and 853 controls to examine the effect of ovulation on ovarian cancer risk. The total number of lifetime ovulations was calculated using information provided in a monthly contraceptive/reproductive calendar, as well as incorporating other information such as average menstrual cycle length. An increase of 1 year's worth of ovulation was associated with a 6% increase in risk of ovarian cancer (95% confidence interval [CI] = 4–8%). Ovulations in the 20–29-year age group were associated with the greatest risk, with a 20% increase in risk associated with each year of ovulation during this age period (95% CI = 13–26%). When the effects of different exposures that suppress ovulation were compared, there was an indication that some factors may have a greater effect than others. These findings support the theory that incessant ovulation is a major contributor to the occurrence of ovarian cancer and suggest that ovulations during the 20s may be those most associated with disease risk. © 2003 Wiley-Liss, Inc.

A major risk factor for breast cancer is having a first-degree family history of the disease. Benign breast disease (BBD), particularly atypical hyperplasia, is also associated with an increased risk of breast cancer. However, the relationship between family history of breast cancer and BBD is unclear. From 1989 through 1997, 80,995 participants in the Nurses' Health Study II were followed; 16,849 reported a first diagnosis of BBD. Pathology slides were reviewed for 1,465 women who reported having a tissue biopsy, and these were classified as nonproliferative BBD, proliferative BBD without atypia or atypical hyperplasia. Women with a family history of breast cancer were more likely to report a physician diagnosis of BBD [rate ratio (RR) = 1.38, 95% confidence interval (CI) 1.29–1.46]. The magnitude of this association declined with age from RR = 1.96 (95% CI 1.55–2.47) at 25–29 years to RR = 1.20 (95% CI 0.95–1.52) at age 45–50 years. Among women with proliferative disease, those with a family history of breast cancer were almost 3 times as likely to have atypia (prevalence odds ratio = 2.72, 95% CI 1.23–5.89) than those with no family history. In conclusion, women with a family history of breast cancer appear to be at increased risk of being diagnosed with BBD, in particular the high-risk types of BBD associated with a greatly increased risk of breast cancer. This link adds weight to the belief that BBD with atypia is a precursor or marker lesion for breast cancer. © 2002 Wiley-Liss, Inc.

Epidemiological studies suggest that ovarian cancer is an endocrine-related tumour, and progesterone exposure specifically may decrease the risk of ovarian cancer. To assess whether the progesterone receptor (PR) exon 4 valine to leucine amino acid variant is associated with specific tumour characteristics or with overall risk of ovarian cancer, we examined 551 cases of epithelial ovarian cancer and 298 unaffected controls for the underlying G→T nucleotide substitution polymorphism. Stratification of the ovarian cancer cases according to tumour behaviour (low malignant potential or invasive), histology, grade or stage failed to reveal any heterogeneity with respect to the genotype defined by the PR exon 4 polymorphism. Furthermore, the genotype distribution did not differ significantly between ovarian cancer cases and unaffected controls. Compared with the GG genotype, the age-adjusted odds ratio (95% confidence interval) for risk of ovarian cancer was 0.78 (0.57–1.08) for the GT genotype, and 1.39 (0.47–4.14) for the TT genotype. In conclusion, the PR exon 4 codon 660 leucine variant encoded by the T allele does not appear to be associated with ovarian tumour behaviour, histology, stage or grade. This variant is also not associated with an increased risk of ovarian cancer, and is unlikely to be associated with a large decrease in ovarian cancer risk, although we cannot rule out a moderate inverse association between the GT genotype and ovarian cancer.

The phase II glutathione S-transferases (GSTs) GSTT1, GSTM1 and GSTP1 catalyse glutathione-mediated reduction of exogenous and endogenous electrophiles. These GSTs have broad and overlapping substrate specificities and it has been hypothesized that allelic variants associated with less effective detoxification of potential carcinogens may confer an increased susceptibility to cancer. To assess the role of GST gene variants in ovarian cancer development, we screened 285 epithelial ovarian cancer cases and 299 unaffected controls for the GSTT1 deletion (null) variant, the GSTM1 deletion (null) variant and the GSTP1 codon 104 A→G Ile→Val amino acid substitution variant. The frequencies of the GSTT1, GSTM1 and GSTP1 polymorphic variants did not vary with tumour behaviour (low malignant potential or invasive) or p53 immunohistochemical status. There was a suggestion that ovarian cancers of the endometrioid or clear cell histological subtype had a higher frequency of the GSTT1 and GSTM1 deletion genotype than other histological subgroups. The GSTT1, GSTM1 and GSTP1 genotype distributions did not differ significantly between unaffected controls and ovarian cancer cases (overall or invasive cancers only). However, the GSTM1 null genotype was associated with increased risk of endometrioid/clear cell invasive cancer [age-adjusted OR (95% CI) = 2.04 (1.01–4.09), P = 0.05], suggesting that deletion of GSTM1 may increase the risk of ovarian cancer of these histological subtypes specifically. This marginally significant finding will require verification by independent studies.

Epidemiological studies indicate that ovarian cancer is an endocrine-related tumour. We conducted a case-control comparison to assess the androgen receptor (AR) exon 1 polymorphic CAG repeat length (CAGn) as a risk factor for epithelial ovarian cancer. AR CAGn was determined for 319 case subjects with ovarian adenocarcinoma and 853 unaffected control subjects (comprising 300 unrelated adult female monozygotic twins, and 553 adult females sampled randomly from the population using the electoral rolls). The CAGn distributions of case subjects and control subjects were compared as a continuum, and by dichotomising alleles according to different CAGn cut-points. Logistic regression was used to calculate age-adjusted odds ratio (OR) estimates. Analyzed as a continuous variable, there was no difference between case subjects and control subjects for the smaller, larger or average allele sizes of the CAGn genotype, before or after adjusting for age. The mean (95% CI) for the average CAGn was 22.0 (21.8–22.2) for case subjects and 22.0 (21.9–22.1) for control subjects (p> .9). Analysis of CAGn as a dichotomous variable showed no difference between case subjects and control subjects for the median cutpoint (≥ 22), or for another cut-point previously reported to act as a modifier of breast cancer risk (≥ 29). Our data provide no evidence for an association between ovarian cancer risk and the genotype defined by the AR exon 1 CAGn polymorphism, although we cannot exclude small effects, or threshold effects in a small subgroup. Int. J. Cancer 87:637–643, 2000. © 2000 Wiley-Liss, Inc.

The CYP17 gene encodes the cytochrome P450c17α enzyme, which functions at 2 different points in the steroid biosynthesis pathway, and is considered a candidate susceptibility gene for endocrine-related tumors. A T to C substitution polymorphism exists in the 5' promoter region of this gene, and creates an additional Sp1-type motif. Several studies have examined this polymorphism as a risk factor for breast cancer, but results have been conflicting. We examined 319 cases of ovarian cancer and 298 unaffected controls for the T-C polymorphism. There was no significant difference between cases and controls for the allele frequencies (p = 0.6), or for genotype distribution (p = 0.9). The odds ratio (95% confidence interval) for ovarian cancer was 1.13 (0.70–1.82) for the putative “cancer susceptibility” CC genotype and 1.07 (0.77–1.48) for any C allele (CC or CT genotype). Results were little different after adjustment for age. Stratification of the ovarian cancer cases according to form (benign, low malignant potential or invasive), histology, grade or stage failed to reveal any heterogeneity with respect to CYP17 genotype. Our data provide no evidence for an association between ovarian cancer risk and the genotype defined by the CYP17 5' promoter region T-C polymorphism. Int. J. Cancer 86:436–439, 2000. © 2000 Wiley-Liss, Inc.

Background & Aims:CagA-positive Helicobacter pyloriinfection has been more closely associated with gastric disease than CagA-negative infection. This study evaluated whether geographic variation in the prevalence of CagAcould explain variation in gastric cancer rates. Methods:The Eurogast study was conducted in 17 centers in 13 countries. Gastric cancer rates were calculated for each center, and serum samples from approximately 2850 subjects were assayed for immunoglobulin G antibodies to H. pyloriand CagA and for pepsinogens A and C. Results:The proportion of CagA-positive H. pyloriinfections varied across the centers, but this variation did not explain any more of the variation in gastric cancer rates than H. pylorialone. Subjects with CagA-positive infection had, however, significantly higher pepsinogen levels and a lower pepsinogen A/C ratio than subjects with CagA-negative infection; this pattern was observed consistently across the study centers. Conclusions:Variation in the seroprevalence of CagA did not explain geographic variation in gastric cancer rates any better than H. pylorialone. However, the consistent variation in pepsinogen levels with CagA status across the study centers supports the importance of the role of CagA in the development of gastric disease.

Low intake of foods rich in vitamin C is associated with an increased risk of gastric cancer, and geographic variation in average vitamin C intake, therefore, could explain some of the wide international variation in gastric cancer rates. This multicentre study investigated the relationships between plasma levels of vitamin C, as an indicator of vitamin C intake, and gastric cancer rates, markers of gastritis and other socio-demographic variables. Fasting plasma samples from about 1,400 individuals from 9 centres in 7 countries worldwide were assayed for total vitamin C using a fluorometric assay. There was no association between average plasma vitamin C levels and either gastric cancer mortality or incidence rates in the populations studied. Therefore, variation in fasting plasma vitamin C levels, as an indicator of consumption of vitamin C, does not appear to explain any of the wide geographic variation in gastric cancer rates. Furthermore, there was no association between plasma vitamin C levels and Helicobacter pylori infection, low serum levels of pepsinogen A (as a marker of severe chronic atrophic gastritis) or the presence of DNA adducts in blood leukocyte DNA. Multivariate models showed that fasting plasma vitamin C levels were associated positively with female sex, higher levels of education, never having smoked and increasing height and negatively with number of cigarettes smoked per day and increasing weight. This suggests not only that gender and tobacco smoking, in particular, are important predictors of plasma vitamin C levels but also that their effects are consistent throughout the developed world. Int. J. Cancer 73:684–689, 1997. © 1997 Wiley-Liss, Inc.

In 1985, gastric cancer was the second most common cause of cancer death in the world. The rapid decline in gastric cancer rates over the last few decades has been attributed to a decline in the prevalence of environmental risk factors for gastric cancer and/or an increase in the prevalence of protective factors. One such risk factor could be the bacterium Helicobacter pylori. Epidemiological studies have shown that areas with high gastric cancer rates often have a correspondingly high prevalence of H. pylori and prospective studies have shown that subjects with serological evidence of H. pylori infection were significantly more likely to go on to develop gastric cancer than those who did not.Helicobacter pylori itself does not appear to be either genotoxic or mutagenic. Infection is, however, associated with increased cell turnover, a chronic immune response accompanied by increased levels of reactive oxygen metabolites and a reduction in gastric levels of ascorbic acid, all conditions that could favour the development of cancer. Nonetheless, the majority of those who are infected with H. pylori do not go on to develop gastric cancer and other factors, such as the strain of the infecting organism or consumption of dietary antioxidants including vitamin C, could also affect the risk of cancer.Finally, it has been estimated that more than one third, and possibly as many as 90% of gastric cancers might be attributable to infection with H. pylori. Prevention and treatment of infection are, therefore, possible approaches to reducing gastric cancer rates. It is, however, unclear what, if any, effect eradication of the infection would have on an individual's risk of gastric cancer and, to date, anti-Helicobacter therapy has only been shown to be of potential benefit in the treatment of low grade gastric MALT lymphomas.

Background/Aims:Low serum levels of pepsinogen A are indicative of chronic atrophy, a risk factor for gastric cancer. This study investigated the relationships between low pepsinogen A levels, Helicobacter pyloriseropositivity, and gastric cancer rates in 17 populations worldwide. Methods:In each center, about 200 randomly selected subjects (50 male and 50 female, aged 25–34 and 55–64 years) provided serum samples for pepsinogen analysis and H. pyloriserology. Results:Cumulative gastric cancer rates were associated with the prevalence of low pepsinogen A levels in men (coefficient, 0.15 [P= 0.06] for mortality; coefficient, 0.36 [P= 0.01] for incidence) but not women. The prevalence of low pepsinogen A levels was also correlated with H. pyloriseropositivity in the older age group (r= 0.55; P= 0.02). Low pepsinogen A levels were significantly more common in the older group (7.5% vs. 2.1% in the younger group; P< 0.001), among women (5.5% vs. 4.1% in men; P= 0.04), and among nonsmokers (5.8% vs. 2.9% in current smokers; P= 0.001). Conclusions:Low pepsinogen A levels are more common in areas with a high seroprevalence of H. pyloriand in men in areas with high rates of gastric cancer. The prevalence of low pepsinogen A levels increases with age, but the excess in women and nonsmokers could reflect factors other than gastric pathology.

Although most women diagnosed with ovarian cancer initially respond to first-line chemotherapy, the vast majority eventually relapses and requires retreatment with second-line chemotherapy. Patient response is classified as either platinum sensitive or platinum resistant on the basis of the time of relapse after first-line treatment. A cancer with a progression-free interval of more than 6 months after completion of first-line chemotherapy is classified as “platinum-sensitive disease” and responds well to retreatment. A cancer with a progression-free interval of less than 6 months after completion of first-line chemotherapy is classified as “platinum-resistant disease” and responds poorly to second-line retreatment. Cure is not possible in patients with platinum-resistant recurrent ovarian cancer, and long-term progression-free survival is rare. The goal of care in these patients should be to maximize their quality of life.

IMPORTANCE: Breastfeeding has been associated with a reduced risk of epithelial ovarian cancer in multiple studies, but others showed no association. Whether risk reduction extends beyond that provided by pregnancy alone or differs by histotype is unclear. Furthermore, the observed associations between duration and timing of breastfeeding with ovarian cancer risk have been inconsistent. OBJECTIVE: To determine the association between breastfeeding (ie, ever/never, duration, timing) and ovarian cancer risk overall and by histotype. DESIGN, SETTING, AND PARTICIPANTS: A pooled analysis of parous women with ovarian cancer and controls from 13 case-control studies participating in the Ovarian Cancer Association Consortium was performed. Odds ratios (ORs) and 95% CIs of the overall association were calculated using multivariable logistic regression and polytomous logistic regression for histotype-specific associations. All data were collected from individual sites from November 1989 to December 2009, and analysis took place from September 2017 to July 2019. EXPOSURES: Data on breastfeeding history, including duration per child breastfed, age at first and last breastfeeding, and years since last breastfeeding were collected by questionnaire or interview and was harmonized across studies. MAIN OUTCOMES AND MEASURES: Diagnosis of epithelial ovarian cancer. RESULTS: A total of 9973 women with ovarian cancer (mean [SD] age, 57.4 [11.1] years) and 13 843 controls (mean [SD] age, 56.4 [11.7] years) were included. Breastfeeding was associated with a 24% lower risk of invasive ovarian cancer (odds ratio [OR], 0.76; 95% CI, 0.71-0.80). Independent of parity, ever having breastfed was associated with reduction in risk of all invasive ovarian cancers, particularly high-grade serous and endometrioid cancers. For a single breastfeeding episode, mean breastfeeding duration of 1 to 3 months was associated with 18% lower risk (OR, 0.82; 95% CI, 0.76-0.88), and breastfeeding for 12 or more months was associated with a 34% lower risk (OR, 0.66; 95% CI, 0.58-0.75). More recent breastfeeding was associated with a reduction in risk (OR, 0.56; 95% CI, 0.47-0.66 for &lt;10 years) that persisted for decades (OR, 0.83; 95% CI, 0.77-0.90 for ≥30 years; P for trend = .02). CONCLUSIONS AND RELEVANCE: Breastfeeding is associated with a significant decrease in risk of ovarian cancer overall and for the high-grade serous subtype, the most lethal type of ovarian cancer. The findings suggest that breastfeeding is a potentially modifiable factor that may lower risk of ovarian cancer independent of pregnancy alone.