An understanding of the etiologic heterogeneity of ovarian cancer is important for improving prevention, early detection, and therapeutic approaches. We evaluated 14 hormonal, reproductive, and lifestyle factors by histologic subtype in the Ovarian Cancer Cohort Consortium (OC3).Patients and Methods Among 1.3 million women from 21 studies, 5,584 invasive epithelial ovarian cancers were identified (3,378 serous, 606 endometrioid, 331 mucinous, 269 clear cell, 1,000 other). By using competingrisks Cox proportional hazards regression stratified by study and birth year and adjusted for age, parity, and oral contraceptive use, we assessed associations for all invasive cancers by histology. Heterogeneity was evaluated by likelihood ratio test. ResultsMost risk factors exhibited significant heterogeneity by histology. Higher parity was most strongly associated with endometrioid (relative risk [RR] per birth, 0.78; 95% CI, 0.74 to 0.83) and clear cell (RR, 0.68; 95% CI, 0.61 to 0.76) carcinomas (P value for heterogeneity [P-het] , .001). Similarly, age at menopause, endometriosis, and tubal ligation were only associated with endometrioid and clear cell tumors (P-het # .01). Family history of breast cancer (P-het = .008) had modest heterogeneity. Smoking was associated with an increased risk of mucinous (RR per 20 pack-years, 1.26; 95% CI, 1.08 to 1.46) but a decreased risk of clear cell (RR, 0.72; 95% CI, 0.55 to 0.94) tumors (P-het = .004). Unsupervised clustering by risk factors separated endometrioid, clear cell, and low-grade serous carcinomas from high-grade serous and mucinous carcinomas. ConclusionThe heterogeneous associations of risk factors with ovarian cancer subtypes emphasize the importance of conducting etiologic studies by ovarian cancer subtypes. Most established risk factors were more strongly associated with nonserous carcinomas, which demonstrate challenges for risk prediction of serous cancers, the most fatal subtype.

Higher circulating 25(OH)D was related to a statistically significant, substantially lower colorectal cancer risk in women and non-statistically significant lower risk in men. Optimal 25(OH)D concentrations for colorectal cancer risk reduction, 75-100 nmol/L, appear higher than current IOM recommendations.

Background Factors contributing to chronic inflammation appear to be associated with increased risk of ovarian cancer. The purpose of this study was to assess the association between circulating levels of inflammation mediators and subsequent risk of ovarian cancer. Methods We conducted a case-control study of 230 cases and 432 individually-matched controls nested within three prospective cohorts to evaluate the association of pre-diagnostic circulating levels of inflammation-related biomarkers (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p40, IL-12p70, IL-13, TNFα, IL-1Ra, sIL-1RII, sIL-2Ra, sIL-4R, sIL-6R, sTNF-R1, and sTNF-R2) measured using Luminex xMap™ technology with risk of ovarian cancer. Results We observed a trend across quartiles for IL-2 (ORQ4 vs. Q1: 1.57, 95% CI: 0.98, 2.52, p= 0.07), IL-4 (ORQ4 vs. Q1: 1.50, 95% CI: 0.95, 2.38, p= 0.06), IL-6 (ORQ4 vs. Q1: 1.63, 95% CI: 1.03, 2.58, p= 0.03), IL-12p40 (ORQ4 vs. Q1: 1.60, 95% CI: 1.02, 2.51, p= 0.06), and IL-13 (ORQ4 vs. Q1: 1.42, 95% CI: 0.90, 2.26, p= 0.11). Trends were also observed when cytokines were modeled on the continuous scale for IL-4 (p-trend=0.01), IL-6 (p-trend=0.01), IL-12p40 (p-trend=0.01), and IL-13 (p-trend=0.04). Odds ratios were not materially different after excluding cases diagnosed less than five years after blood donation or when limited to serous tumors. Conclusions and Impact This study provides the first direct evidence that multiple inflammation markers, specifically IL-2, IL-4, IL-6, IL-12, and IL-13, may be associated with risk of epithelial ovarian cancer, and adds to the evidence that inflammation is involved in the development this disease.