Final analysis of the PROMISE-GIM6 phase III trial assessing GnRH agonist use during chemotherapy as a strategy to preserve ovarian function in premenopausal patients with early breast cancer.

516 Background: Current guidelines recommend GnRH agonist (GnRHa) use during chemotherapy (CT) as a strategy to reduce the risk of premature ovarian insufficiency (POI) in premenopausal patients with early breast cancer (EBC). However, no long-term safety data are available raising some concerns on concurrent use of GnRHa during CT in patients with hormone receptor-positive disease. In addition, there is no evidence on the protective role of this strategy in patients with germline BRCA mutations ( mBRCA). Here, we report the final analysis of the PROMISE-GIM6 phase III randomized study, the largest trial addressing the role of GnRHa use during CT in premenopausal EBC patients (Del Mastro et al, JAMA 2011 & Lambertini et al, JAMA 2015). Methods: From October 2003 to January 2008, 281 premenopausal patients aged 18 to 45 years with stage I-III EBC candidates for (neo)adjuvant CT were randomized to receive CT alone or combined with the GnRHa triptorelin. Primary endpoint was incidence of CT-induced POI (defined as amenorrhea and post-menopausal FSH/estradiol levels 1 year following CT). This final analysis reports on post-treatment pregnancies, disease-free survival (DFS) and overall survival (OS). An exploratory descriptive analysis in mBRCA patients is also reported. (ClinicalTrial.gov: NCT00311636) Results: Of the 281 randomized patients (CT+GnRHa arm = 148; CT alone arm = 133), 80% had hormone receptor-positive disease. At the time of this final analysis, 38 (13.5%) patients were lost to follow-up. Median follow-up was 12.4 years (IQR: 11.3-13.2 years). In the CT+GnRHa and CT alone arms, respectively, 9 (10-year cumulative incidence of pregnancy 6.5%, 95% CI 3.5%-12.3%) and 4 (10-year cumulative incidence of pregnancy 3.2%, 95% CI 1.2%-8.3%) patients had a post-treatment pregnancy (HR 2.14, 95% CI 0.66-6.92). No differences in 10-year DFS (72.4% in CT+GnRHa arm vs. 71.2% in CT alone arm: HR 1.16, 95% CI 0.76-1.77) nor in 10-year OS (82.0% in CT+GnRHa arm vs. 85.9% in CT alone arm: HR 1.17, 95% CI 0.67-2.03) were observed. There was no interaction between treatment effect and hormone receptor status. In patients with hormone receptor-positive disease, HR was 1.02 (95% CI 0.63-1.63) for DFS and 1.12 (95% CI 0.59-2.11) for OS. Out of 43 patients tested for BRCA, overall incidence of POI, irrespective of treatment arm, was 20% in mBRCA patients (n = 10) and 12% in patients without mBRCA (n = 33). In mBRCA patients, incidence of POI was 0% and 33% in the CT+GnRHa and CT alone arms, respectively. One post-treatment pregnancy was described in a patient with mBRCA1 in the CT alone arm. Conclusions: The final analysis of the PROMISE-GIM6 trial at a median follow-up of 12.4 years provides reassuring evidence on the safety of GnRHa use during CT as a strategy to preserve ovarian function in premenopausal patients with hormone receptor-positive EBC. Clinical trial information: NCT00311636.