The prognostic role of post-induction FDG-PET in patients with follicular lymphoma: a subset analysis from the FOLL05 trial of the Fondazione Italiana Linfomi (FIL).

[18F]fluorodeoxyglucose-positron emission tomography (PET) is emerging as a strong diagnostic and prognostic tool in follicular lymphoma (FL) patients.In a subset analysis of the FOLL05 trial (NCT00774826), we investigated the prognostic role of post-induction PET (PI-PET) scan. Patients were eligible to this study if they had a PI-PET scan carried out within 3 months from the end of induction immunochemotherapy. Progression-free survival (PFS) was the primary study end point.A total of 202 patients were eligible and analysed for this study. The median age was 55 years (range 33-75). Overall, PI-PET was defined as positive in 49 (24\%) patients. Conventional response assessment with CT scan was substantially modified by PET: 15\% (22/145) of patients considered as having a complete response (CR) after CT were considered as having partial response (PR) after PI-PET and 53\% (30/57) patients considered as having a PR after CT were considered as a CR after PI-PET. With a median follow-up of 34 months, the 3-year PFS was 66\% and 35\%, respectively, for patients with negative and positive PI-PET (P<0.001). At multivariate analysis, PI-PET (hazard ratio 2.57, 95\% confidence interval 1.52-4.34, P