Obesity-Related Cancers in Relation to Use of Statins and Testosterone Replacement Therapy Among Older Women: SEER-Medicare 2007–2015

<b>Background/Objectives</b>: The associations of statins and testosterone replacement therapy (TTh) with the risk of obesity-related cancers (ORC, breast [BrCa], colorectal [CRC], ovarian, and endometrial cancers) in older women remain poorly understood. This study examined the associations between the use of statins and TTh with risk of ORC and its cancer-specific sites in women aged 65 years and older. <b>Methods</b>: A retrospective cohort study was conducted using 2007-2015 SEER-Medicare data, including 142,772 women aged ≥ 65 years. We identified 52,086 women with incident ORC (BrCa [n = 32,707], CRC [n = 11,070], ovarian [n = 2601], and endometrial [n = 5708] cancers). The primary exposures were use of statins and TTh. Weighted multivariable time-dependent Cox proportional hazards and models were conducted to estimate hazard ratios (HRs) of incident ORC. <b>Results</b>: We found an inverse association of statins with incident [HR, 0.76; 95% CI: 0.74, 0.78], high-grade [HR, 0.75; 95% CI: 0.72, 0.78], and advanced-stage [HR, 0.91; 95% CI: 0.88, 0.95] ORC. Concurrent use of statins and TTh was associated with a reduced incidence of ORC and high-grade ORC. Similar associations were observed with BrCa. Statins were inversely associated with high-grade ovarian cancer and endometrial cancer (incident, high-grade, and advanced-stage). <b>Conclusions</b>: Use of statins was inversely associated with ORC, BrCa, and endometrial cancer (high-grade and advanced-stage) and high-grade ovarian cancer in older women. Concurrent use of statins and TTh was inversely associated with ORC and BrCa and their high-grade disease. Future prospective studies are needed to substantiate these findings, especially with a focus to examine time- and dose-response associations and to identify underlying biological mechanisms through which statins and TTh influence incidence of ORC.