Expanding Our Understanding of Ovarian Cancer Risk: The Role of Incomplete Pregnancies
Open Access
- 7 August 2020
- journal article
- research article
- Published by Oxford University Press (OUP) in JNCI Journal of the National Cancer Institute
- Vol. 113 (3), 301-308
- https://doi.org/10.1093/jnci/djaa099
Abstract
Parity is associated with decreased risk of invasive ovarian cancer; however, the relationship between incomplete pregnancies and invasive ovarian cancer risk is unclear. This relationship was examined using 15 case-control studies from the Ovarian Cancer Association Consortium (OCAC). Histotype-specific associations, which have not been examined previously with large sample sizes, were also evaluated. A pooled analysis of 10 470 invasive epithelial ovarian cancer cases and 16 942 controls was conducted. Odds ratios (ORs) and 95% confidence intervals (CIs) for the association between incomplete pregnancies and invasive epithelial ovarian cancer were estimated using logistic regression. All models were conditioned on OCAC study, race and ethnicity, age, and education level and adjusted for number of complete pregnancies, oral contraceptive use, and history of breastfeeding. The same approach was used for histotype-specific analyses. Ever having an incomplete pregnancy was associated with a 16% reduction in ovarian cancer risk (OR = 0.84, 95% CI = 0.79 to 0.89). There was a trend of decreasing risk with increasing number of incomplete pregnancies (2-sided Ptrend < .001). An inverse association was observed for all major histotypes; it was strongest for clear cell ovarian cancer. Incomplete pregnancies are associated with a reduced risk of invasive epithelial ovarian cancer. Pregnancy, including incomplete pregnancy, was associated with a greater reduction in risk of clear cell ovarian cancer, but the result was broadly consistent across histotypes. Future work should focus on understanding the mechanisms underlying this reduced risk.Funding Information
- Ovarian Cancer Research Fund
- Kathryn Sladek Smith (PPD/RPCI.07)
- US National Cancer Institute at the National Institutes of Health (GAME-ON Post-GWAS, U19-CA148112)
- US Army Medical Research and Materiel Command (DAMD17-01–1-0729)
- The Cancer Council Tasmania and The Cancer Foundation of Western Australia
- National Health and Medical Research Council of Australia (ID199600, ID400413, ID400281)
- National Institutes of Health (R01-CA063678, R01-CA074850, R01-CA080742)
- National Institutes of Health (R01-CA112523, R01-CA87538)
- National Institutes of Health (K22 CA193860)
- German Federal Ministry of Education and Research
- Programme of Clinical Biomedical Research (01 GB 9401)
- German Cancer Research Center
- US National Institutes of Health (R01-CA58598, N01-CN-55424, N01-PC-67001)
- Department of Defense (DAMD17-02–1-0669)
- National Cancer Institute at the National Institutes of Health (K07-CA080668, R01-CA95023, P50-CA159981MAL)
- National Cancer Institute at the National Institutes for Health (R01- CA61107)
- Danish Cancer Society (94 222 52)
- Mermaid I
- National Institutes of Health (R01-CA76016)
- Department of Defense (DAMD17-02–1-0666)
- National Institutes of Health (R01-CA54419, P50-CA105009)
- Department of Defense (W81XWH-10–1-02802)
- National Cancer Institute at the National Institutes for Health (NIH-K07 CA095666, R01-CA83918, NIH-K22-CA138563, P30-CA072720)
- Cancer Institute of New Jersey
- Intramural Research Program of the National Cancer Institute
- National Institutes of Health (U01 CA71966, U01 CA69417)
- National Institutes of Health (R01-CA058860)
- Lon V Smith Foundation (LVS-39420)
- The Eve Appeal
- National Institute for Health Research University College London Hospitals Biomedical Research Centre
- MRC Core Funding (MR_UU_12023)
- National Institutes of Health (P01CA17054, P30CA14089, R01CA61132, N01PC67010, R03CA113148, R03CA115195, N01CN025403)
- California Cancer Research Program (00–01389 V-20170, 2II0200)
- NIH/NCI (P30 CA008748)
- Memorial Sloan Kettering Cancer Center
- Scientific Scholar Award from the Rivkin Center for Ovarian Cancer
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