LAUSR

1086Background: CTCs are strongly associated with prognosis in MBC. In a recent metanalysis on 1944 patients, a CTC count > 5/7.5 ml was associated with a 2-fold increased risk of progression and death. Little evidence is available on the prognostic role of phenotypic CTC assessment, however. In this study, nested in a randomized clinical trial of Ist line chemotherapy ± metformin, we evaluated the prognostic role of IGF1R expression in CTCs, given its potential growth promoting effect. Methods: CTCs were isolated from blood samples of enrolled patients; an automated sample preparation and analysis system (CellSearch) was customized for detecting IGF1R positive CTCs. The prognostic role of total CTCs, IGF1R positive (+ve) and negative (-ve) CTCs was assessed by fitting different PFS and OS multivariate Cox’s models.Results: CTC evaluation at baseline was performed in 72 of 126 patients, of whom 30 (42%) had CTCs ≥5/7,5ml and 41 (57%) had at least one IGF1R+ve CTC. In univariate analysis the prognostic rol...