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Use of ovarian suppression with endocrine therapy among premenopausal United States women with breast cancer, 2001-2016.

e12010 Background: Clinical trials indicate that adding ovarian suppression (OS) to endocrine therapy (ET) in premenopausal women with non-metastatic breast cancer improves disease-free and overall survival. However, injectable OS may add cost, potential side effect burden, and additional clinic visits to adjuvant therapy. It is not known to what extent OS is being used in contemporary community oncology settings. Methods: We identified women age 18-50 with incident breast cancer based on diagnosis codes from 2001-2016 in the commercial IBM MarketScan database. Eligible patients were continuously enrolled for a year prior to cancer diagnosis and filled at least 1 prescription for oral ET (i.e., tamoxifen, toremifene, anastrozole, letrozole, and/or exemestane) in the year after diagnosis. We classified use of OS as any prescription for a gonadotropin-releasing hormone agonist in outpatient pharmacy claims or procedure code for OS implant or injection 1) in the week prior to ET initiation or 2) following ET initiation and for up to 18 months after diagnosis. We estimated the proportion of women that were OS users in each diagnosis year using linear binomial regression, and examined associations between OS use, age at diagnosis, and geographic region. Results: A total of 26,114 women meeting all inclusion criteria were identified from the MarketScan database, of whom 1,452 (5.6%) were OS users. The most common OS drug was leuprolide or leuprorelin (55.2%), followed by goserelin (46.7%), and triptorelin (1.1%). Risk of OS use varied from 3.2% in 2001 to 9.3% in 2016, peaking at 11.4% in 2015. OS use varied by region (χ2 p = 0.0003), with the highest use observed in the Northeast (6.5%) and the lowest in the South (5.0%). Younger patients were significantly more likely to use OS than older patients, with each additional year of age at diagnosis associated with a 0.57 percentage point lower risk (95% confidence interval [CI]: -0.63, -0.51). After controlling for age group (≤40, 41-44, 45-46, 47-48, 49-50) and region, each additional calendar year was associated with 0.25 percentage point greater risk of OS use (95% CI: 0.19, 0.31). Conclusions: OS use with ET appears to be increasing in US breast oncology practice among women under 50.