Ovarian cancer risk factors by histologic subtypes in the NIH-AARP Diet and Health Study

Tuesday, October 25, 2011 — Poster Session II
Noon – 2:00 p.m.	Natcher Conference Center	NCI	EPID-16

Authors

• H Yang
• B Trabert
• M Murphy
• M Sherman
• J Sampson
• L Brinton
• P Hartge
• A Hollenbeck
• Y Park
• N Wentzensen

Abstract

Data suggest that ovarian carcinoma risk factors vary by histologic type, suggesting that ovarian carcinoma may constitute several distinct entities. We evaluated risk factors by histological subtypes among 849 incident ovarian cancers in 169,391 women in the NIH-AARP Diet and Health Study. We constructed Cox models to compare case subtypes to the non-case group and assessed P-heterogeneity in case-case comparisons using serous carcinoma as the referent. Several risk factor associations showed heterogeneity by histologic subtypes and were similar to associations for phenotypically similar cancers. Notably, obesity was positively associated only with endometrioid ovarian cancers (relative risk (RR)=1.64; 95% confidence interval (CI): 1.00, 2.70), consistent with increased risk generally reported for endometrial cancer. We also observed substantial risk differences between histologic subtypes for menopausal hormone therapy (MHT) use, oral contraceptive (OC) use, and parity (P-heterogeneity=0.01, 0.03, 0.05, respectively). We observed only decreased risk among MHT users for mucinous (RR=0.37; 95% CI: 0.18, 0.80) and OC users for serous (RR=0.69; 95% CI: 0.55, 0.85). Parity was inversely associated for all subtypes, but RRs ranged from 0.28 (clear cell) to 0.83 (serous). Despite limitations of statistical power and diagnostic misclassification, our findings suggest a link between etiological and histological heterogeneity in ovarian carcinoma.

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