Abstract P4-01-03: Predictive value of FDG-PET/CT after neoadjuvant endocrine treatment in breast cancer

Abstract

Abstract Background: Neaodjuvant endocrine therapy (NET) has demonstrated efficacy in terms of clinical response and outcome in hormone-receptor positive (HR+) post-menopausal patients (pts) with breast cancer (BC) not eligible for primary breast conservative surgery (BCS). However, the monitoring of tumor response to NET is challenging and clinical response is the current gold standard. The aim of the present study was to investigate the contribution of the early metabolic response (eMR) at one month in FDG-PET/CT in a NET setting for post-menopausal pts with HR+, HER2- BC compared to morphological and pathological responses. We also aimed to evaluate the prognostic value of eMR. Methods: This was a prospective and ancillary study of CARMINA 02, UCBG0609 (Cancer in press), a phase II clinical trial evaluating the efficacy of 4 to 6 months neoadjuvant anastrozole or fulvestrant. FDG-PET/CT exams were performed at baseline (M0), after 1 month of treatment (M1: eMR) and pre-Op (late metabolic response: lMR) in 11 pts (74.2 years ± 3.6) from 2007 to 2010. Pts were classified “metabolic responders” (mR) if SUVmax values decrease was ≥ 40% at M1 and “non-metabolic responders” (mNR) if otherwise; lMR was also assessed in mR and mNR groups defined at M1. We compared eMR to morphological response (clinical, breast US and MRI) at M1 and pre-op, to the pathological response according to Sataloff classification and to Ki67 score variation during treatment. Early metabolic response was also correlated with the PEPI (Preoperative Endocrine Prognostic Index) score and survival (overall survival, OS and relapse free survival, RFS). Results: Main results are summarized in Table I. There was a significant difference between mR and mNR pts at M1 (eMR) and pre-op (lMR). One patient with a complete metabolic response at pre-op had the best pathological response (Sataloff TB). Also, mR pts had a better clinical response: 2 partial response (PR) in mR vs 1 in mNR group and 2 mNR patients were classified PD (progressive disease). There was a trend toward better survival for mR pts in OS and RFS (Kaplan-Meier p=0.18 and 0.06, respectively) and all the pejorative events occurred in the mNR group: 3 deaths and 3 metastatic progressions. Besides, no difference in eMR was observed regarding the histological subtype (ductal or lobular; p>0.05) nor the treatment group (p>0.05). Table I: Metabolic, morphological and pathological response at M1, Pre-Op and on the surgical specimen. MR : 5ptsmNR : 6ptsP valueM1SUVmax2.6±1.13.9±1.40.00017 Clinical size42.5mm±11.951.7mm±7.50.19 US size22.6mm±6.334.2mm±2.40.02 MRI size21.2mm±4.239.7mm±4.79.16 E-5 Ki 673.6%±1.98.2%±80.19Pre-OpSUVmax2±1.33.3±1.40.018 Clinical size31mm±12.448.3mm±10.80.035 US size18.5mm±7.331.3mm±9.50.07 MRI size17.9mm±7.134.8mm±7.70.003Surgical SpecimenSataloff (TA+TB vs TC+TD)20% vs 80%0 vs 100%1 PEPI score (I+II vs III)80% vs 20%33 vs 67%0.048 Ki 678.6%±9.812.3%±7.90.41 Conclusions: These preliminary results showed the value of the early metabolic response in FDG- PET/CT in a NET setting compared to the morphological or the pathological responses alone. Early metabolic responders patients had better OS, RFS and PEPI scores. Citation Format: Boughdad S, Champion L, Becette V, Cherel P, Fourme E, Edeline V, Lemonnier J, Lerebours F, Alberini JL. Predictive value of FDG-PET/CT after neoadjuvant endocrine treatment in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-01-03.