2ndconservative Treatment for 2ndipsilateral Breast Tumor Event: Mature Oncological Results and Prognostic Factors from the GEC-Estro Bcwg.

Abstract

In case of second ipsilateral breast tumor event (2ndIBTE) occurring after primary radio-surgical treatment, salvage mastectomy or 2ndconservative treatment (2ndCT) including an accelerated partial breast re-irradiation (APBrI) can be discussed according to patient and tumor features. We report updated results from the database of the GEC-ESTRO Breast Cancer Working Group. Between 2000 and 2014, 343 patients (pts) underwent a 2ndCT in 12 hospital/cancer centers from 7 European countries. After lumpectomy, APBrI was performed using either low (30 – 55 Gy reference isodose) or high dose-rate brachytherapy (28 - 34 Gy). Oncological outcome including 3rdIBTE-free survival and overall survival (OS) was analyzed. Univariate (UVA) and multivariate analyses (MVA) were conducted to identify significant prognostic factors for 3rdIBTE including the belonging to one of the 3 sub-groups of the GEC-ESTRO APBI classification (GAC) and the tumor molecular profile (MP - JAMA. 2019;321:288-300). Late toxicity was reported. With a median follow-up of 72 months (range: 64 - 80 months), 150 pts (44%), 144 pts (42 %) and 49 pts (14%) were classified as low (LR), intermediate (IR) and high-risk (HR) respectively. Regarding the molecular profile (excluding in situ carcinomas), 233 pts (77%), 28 pts (10%) and 40 pts (13%) were positive hormonal receptors (HR+), over-expressed Her2 (Her2+) and triple negative (TN) respectively. For the whole cohort, 6-year 3rdIBTE-free survival and OS rates were 94.6% and 85.9% respectively. For the cohort excluding in situ carcinomas, 6-year 3rdIBTE-free survival and OS rates were 93.8% and 84.8% respectively. In UVA, SBR (1,2 vs 3 - p = 0.008), age (< 50 y vs. 50 y - p = 0.001), GAC (p = 0.001) and MP (p = 0.05) were considered as significant prognostic factors for 3rdIBTE, while, in MVA, SBR (HR 3.3 CI: 1.269 - 8.585; p = 0.01) and GAC (HR 8.4 CI: 1.878 - 37.864; p = 0.004) were the two remaining prognostic factors. In terms of late toxicity, 194 pts (87%) presented G1,2 complications while G>=3 complication rate was 13%. In case of 2ndIBTE, 2ndCT combining re-lumpectomy + APBrI represent a valid therapeutic option in terms of oncological outcome as well as toxicity profile. Patient and tumor characteristics have to be carefully evaluated while patient information remains crucial for the discussion of treatment choice.