Factors With Adequate Evidence of an Increased Risk of Ovarian Cancer
Hormone replacement therapy/hormone therapy
A modest association between current, but not past, postmenopausal hormone therapy use and incident ovarian cancer was observed in the Million Women Study. The Million Women Study reported on 2,273 incident cases of ovarian cancer observed among women followed for an average of 5.3 years. The relative risk (RR) among current users of hormone therapy compared with women who never used hormone therapy was 1.20 (95% confidence interval [CI], 1.09–1.32). A dose-response relationship was observed with increasing risk, noted with increasing duration of use. The observed RRs were higher for estrogen-only therapy than for combined estrogen-progestogen therapy (RR, 1.34; 95% CI, 1.13–1.60 vs. RR, 1.14; 95% CI, 1.01–1.28, respectively). No excess risk of ovarian cancer was observed among past users.
As in the Million Women Study, a population-based case-control study conducted in Washington State observed an association between ovarian cancer and current or recent use (within the last 3 years) of exclusively estrogen-only therapy for at least 5 years (current use: odds ratio [OR], 1.6; 95% CI, 1.1–2.5; recent use: OR, 1.8; 95% CI, 0.8–3.7). However, no increased risk was observed among users of combined estrogen-progestogen therapy.
The Women's Health Initiative estrogen-progestin randomized trial observed a nonstatistically significant excess risk of ovarian cancer, based on 32 cases of ovarian cancer at the 5.6-year follow-up (hazard ratio, 1.58; 95% CI, 0.77–3.24). An accelerated decline in ovarian cancer incidence rates after 2002—following the report of the Women's Health Initiative and subsequent decline in the use of hormone therapy—supports, but does not prove, a causal association between hormone therapy and ovarian cancer risk.
A cohort study among nurses did not observe a risk of ovarian cancer associated with perineal talc use (RR, 1.09; 95% CI, 0.86–1.37). A meta-analysis of 16 studies observed an increased risk with the use of talc (RR, 1.33; 95% CI, 1.16–1.45); however, there was no evidence of a dose response. A pooled analysis from the Ovarian Cancer Association Consortium that included 8,525 cases and 9,859 controls observed a modest increased risk of epithelial ovarian cancer associated with genital powder use (OR, 1.24; 95% CI, 1.15–1.33). Risks assessed across quartiles of lifetime number of applications, compared with women who never used talc, was 1.18 (1.02–1.36), 1.22 (1.06–1.41), 1.22 (1.06–1.41), and 1.37 (1.19–1.58) (Ptrend = .17). Perineal application of talc is associated with a small increased risk of ovarian cancer. The International Agency for Research on Cancer (IARC) has concluded that perineal talc is a possible carcinogen.[13,14]