Adjuvant exemestane or tamoxifen plus ovarian suppression in premenopausal women: single institution analysis

Background: The combined analysis of data from TEXT and SOFT trials shows that among premenopausal women with hormone receptor-positive (HR+) breast cancer (BC), adjuvant endocrine therapy (AET) with exemestane (EXE) plus ovarian function suppression (OFS) improved disease-free survival compared to tamoxifen (TAM) plus OFS. We conducted a single institution analysis to compare the activity and safety of both treatment strategies. Patients And Methods: The data on tumor and patient’s characteristics of premenopausal women treated with AET from January 2014 to December 2018 in our institution were retrospectively collected. Treatment toxicities were graded according to CTCAE v5. Survival data were analyzed by Kaplan Meier curves and log rank test. Results: 237 patients were included in the study: 120 on TAM / OFS and 117 on EXE/OFS. Notably, 43 patients (18%) started AET in 2014 (before TEXT/SOFT data): 93% of these were treated with TAM/OFS versus only 7% with EXE/OFS. Women on EXE/OFS had more high-risk early BC compared to those on TAM/OFS (STAGE III 23,9% vs 6,6%; luminal B-like 34,2% vs 21,6%; T> 2 cm 68,4% vs 32,5%; nodal status positive 66,6% vs 36,6% - all p value <0,01). According with risk of relapse, the number of patients pre-treated with chemotherapy was higher in EXE/OFS group (79,5% versus 37,5%, p value <0,001) than TAM/OFS one. Extended therapy was accepted by 50% of patients in the TAM/OFS group and 47% in the EXE/OFS group. Any grade adverse events (AE) were observed in 77 (64%) and 101 (86%) patients in TAM/OFS and EXE/OFS group, respectively. In particular, the incidence of G3 AEs was significantly higher in the EXE/OFS group and mainly represented by muscoloskeletal symptoms, osteoporosis and hypertension. Eighteen (15,4%) women discontinued EXE and switched to an alternate ET (TAM or NSAI) due to treatment toxicity. No statistically significant difference in terms of relapse freesurvival was observed between the two groups. A – Breast Cancer 27 Conclusions: In our analysis, the choice of the AET is driven mainly from the risk of relapse. EXE/OFS represents the main choice in the high-risk patients as per SOFT/ TEXT trials results. TAM/OFS represent the main chose antecedent to the SOFT/TEXT results (2014/2015).The frequency and the grade of AEs were higher in EXE group than TAM one. The AET should be proposed based on both, risk of relapse and treatment toxicity profile. An update analysis will be presented at the meeting.