Predictive factors of 5-year relapse-free survival in HR+/HER2- breast cancer patients treated with neoadjuvant endocrine therapy: pooled analysis of two phase 2 trials

Background Few data are available on survival and predictive factors in early breast cancer (BC) patients treated with neoadjuvant endocrine therapy (NET). Methods This is a pooled analysis of two multicentre, randomised non-comparative phase 2 clinical trials evaluating neoadjuvant anastrozole and fulvestrant efficacy for postmenopausal HR+/HER2- breast cancer patients: HORGEN (NCT00871858) and CARMINA02 (NCT00629616) studies. Results In total, 236 patients were included in CARMINA02 and HORGEN trials. Modified intention-to-treat analysis was available for 217 patients. Median follow-up was 65.2 months. Relapse-free survival (RFS) and overall survival (OS) at 5 years were 83.7% (95% CI: 77.9–88) and 92.7% (95% CI: 88.2–95.6), respectively, with no difference between treatment arms. On univariate analysis, tumour staging (T2 vs T3–4; p = 0.0001), Ki-67 at surgery (≤10% vs >10%; p = 0.0093), pathological tumour size (pT1–2 vs pT3–4; p = 0.0012) and node status (pN negative vs positive; p = 0.007), adjuvant chemotherapy (p = 0.0167) and PEPI score (PEPI group I + II vs III; p = 0.0004) were associated with RFS. No events were observed in patients with pathological response according to the Sataloff classification. Multivariate analysis showed that preoperative endocrine prognostic index (PEPI) group III was associated with significantly worse RFS (p = 0.0069, hazard ratio = 3.33 (95% CI: 1.39–7.98)). Conclusions Postmenopausal HR+/HER2- breast cancer patients receiving NET generally have a favourable outcome. The PEPI score identifies a subset of patients of poorer prognosis who are candidates for further additional treatment.