Background: Menopausal hormone therapy (MHT) increases risk of breast, endometrial, and ovarian cancer. Following the Women's Health Initiative (WHI) report in 2002 linking MHT to increased breast cancer risk, both MHT use and breast cancer rates declined sharply in the US. Subsequently, we reported an accelerated decline in ovarian cancer rates after 2002 using age-period-cohort (APC) modeling to estimate period changes independent of age and birth cohort effects. Given links between MHT and risks for breast, ovarian and endometrial cancer, we compared changes in rates of these tumors following the WHI announcement in 2002 by applying a comparative APC modeling approach.

Methods: Using the North American Association of Central Cancer Registries (NAACCR) database (1995-2010), we created three analytic files for women ages 50 to 84 years (surrogate for menopause): breast (ICD-0-3 codes C500-509; n = 1,597,409), endometrial (C540-549, C559; 340,498), and ovarian (C569; 174,755) cancers. We applied standard (SEER*STAT, joinpoint regression) and APC models to estimate cancer incidence rate changes pre- (1995-2002) and post- (2003-2010) WHI report, to assess temporal changes associated with the decline in MHT prescriptions.

Results: Although age-standardized breast cancer incidence was heterogeneous before and after WHI-report, APC models demonstrated a decline in rates after 2002. Age-standardized endometrial cancer rates declined 0.82%/year (95% CI: -1.44 to -0.19%/year) pre-WHI, after which the rates increased 1.03%/year (95% CI: 0.59 to 1.47%/year). APC models confirmed the increase for endometrial cancer post-WHI. Age-standardized ovarian cancer incidence declined 1.02%/year (95% CI: -1.55 to -0.48%/year) pre-WHI, after which the rates declined 2.36%/year (95% CI: -3.00 to -1.70%/year). APC models showed an accelerated decline in ovarian cancer incidence post-WHI.

Conclusion: Following a marked reduction in MHT use circa 2002, incidence rate trends changed somewhat differently for breast, endometrial and ovarian cancer. Specifically, rising breast cancer rates fell, decreasing endometrial cancer rates increased, and decreasing ovarian cancer rates fell more rapidly. Further analysis by age, race and histological subtype may provide insights into complex etiological differences between these hormone-related tumors.

Citation Format: Hannah P. Yang, William F. Anderson, Britton Trabert, Philip S. Rosenberg, Gretchen L. Gierach, Clara Bodelon, Nicolas Wentzensen, Kathleen A. Cronin, Mark E. Sherman. Incidence trends of breast, endometrial, and ovarian cancer among US women in relation to changing patterns of menopausal hormone therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3700. doi:10.1158/1538-7445.AM2015-3700