Endocrine responsiveness in Estrogen Receptor positive (ER+) MBC is based on the level of ER expression on the primary tumor and/or metastatic lesion. In this study, nested in the ET-FES JTC 2011 TRANSCAN project, we used molecular imaging with 18F-FES to explore intra-patient heterogeneity in ER expression at different metastatic sites and to identify patients who are not likely to benefit from ET.
ER+ patients at first relapse underwent at baseline a 18F-FES PET/CT plus a 18F-fluoro-2-deoxy-D-glucose (FDG) PET/CT. Patients were classified into 4 18F-FES/FDG subgroups based on the proportion of FDG avid metastatic tumor load with high 18F-FES uptake (Gebhart Ann Oncol 2016). Subgroup A was considered positive (100% of concordance); subgroups B and C were considered partially positive or partially negative, with different degrees of 18F-FES uptake; subgroup D was considered negative (100% of discordance). Patients with global SUV ≥2 received first line ET while those with SUV
So far, 80 patients have been enrolled in the ET-FES trial and 79 are included in the present analysis. At baseline evaluation, 53 patien4ts (67.1%) were classified as 18F-FDG/18F-FES positive (A); 16 patients (20.3%) showed some degree of intra-patient heterogeneity (11 group B and 5 group C); 10 patients (12.6%) were classified as D with all lesions being 18F-FES negative. In the 64 patients with a response evaluation available at time of analysis, 26 have shown progression. ET was administered in 40 patients in group A and in 24 patients in groups B + C + D. The use of ET alone in partially positive (B) or partially negative (C) or negative (D) patients was associated with a 79% absolute increase in the risk of progression (HR 1.79, p 0.2) compared to patients in group A.
Pretreatment ER biomarker imaging at different metastatic sites with 18F-FES PET/CT indicate the presence of a significant intra-patient heterogeneity in MBC and represents a promising tool to select patients who are unlikely to benefit from ET alone.
Clinical trial identification
Legal entity responsible for the study
E.O. Ospedali Galliera, Genoa, Italy
TRANSCAN JTC 2011
C. Brambati: Employer Advanced Accelerator Applications. All other authors have declared no conflicts of interest.