Estrogen hormone therapy use in ovarian cancer patients under age 60 at diagnosis

OBJECTIVE: To examine the association between post-diagnosis use of estrogen hormone therapy (EHT) and survival among patients diagnosed with invasive epithelial ovarian cancer by histotype before the age of 60. METHODS: In this retrospective, population-based, cohort study, we included all patients diagnosed with invasive epithelial ovarian cancer (EOC) between January 1, 1997, and December 31, 2020, who were under age 60 at diagnosis and survived at least one year after diagnosis. EHT use was restricted to systemic use, defined using provincial pharmacy dispensation records. We compared the survival of post-diagnosis EHT users to hormone therapy (HT) non-users using Cox proportional hazards regression with EHT use as a time-varying exposure and using a landmark analysis. RESULTS: Of the 2334 people included, 19.1% (n = 446) used EHT after their cancer diagnosis. EHT use was significantly associated with improved survival among people with serous ([adjusted hazard ratio [aHR], 0.71, 95% [CI] 0.58-0.87) and clear cell EOC (aHR, 0.52, 95% [CI] 0.28-0.97). As most of serous EOC is high-grade, this improved survival applies to high-grade serous cancer (HGSC). In contrast, EHT users showed worse survival among patients with the endometrioid histotype (aHR, 2.01, 95% [CI] 1.16-3.51). CONCLUSION: Post-diagnosis use of EHT is safe for patients diagnosed under age 60 with HGSC and likely for clear cell EOC. Thus, EHT can be used to manage menopausal sequelae in these patients. Our data suggest caution is warranted in patients with endometrioid EOC. More research is needed to understand the relationship between EHT and mucinous EOC survival.