Interim FDG-PET/CT for therapy monitoring and prognostication in Hodgkin's Lymphoma

The aim of the study was to assess the predictive value of interim FDG-PET/CT (iPET) in patients with Hodgkin's lymphoma (HL) treated with Adriamycin, bleomycin, vinblastine and dacarbazine (ABVD) chemotherapy. A total of 245 consecutive patients with de novo HL between 12/2013 and 12/2017 were evaluated retrospectively. All patients were treated with upfront ABVD, performed PET/CT scans at baseline, after 2 cycles (interim PET, iPET2) or 4 cycles (iPET4) and at the end of therapy, and followed up for at least 6 months after therapy. The response status on iPET was defined according to the standard five-point Deauville scores (DS) as follows: complete metabolic response (CMR, DS 1-3) and non-complete metabolic response (nCMR) (DS 4 and 5). End-of-treatment (EoT) response was assessed by FDG-PET/CT and if needed biopsy confirmation of PET-positive findings. The association between iPET and EoT response was investigated using logistic regression analysis. Survival analysis was performed using the Cox regression hazard model and Kaplan-Meier methods. Sixty-nine patients underwent iPET-2 and 176 iPET-4. No association was found between the timing of iPET and iPET response status (P-value = 0.71). Two hundred and one patients (82%) had iPET-CMR and 44 (18%) iPET -nCMR. iPET was strongly associated with EoT response status: 194/201 (96 .5%) of iPET-CMR had a complete response at the EoT while only 21/44 (47.7%) of patients with iPET-nCMR presented a complete response at EoT (P-value < 0.0001). The median follow-up was 32 months (range 6-81). Patients with iPET-CMR presented a better outcome with 91% 3 y event-free-survival (EFS) and 95% 3 y overall survival (OS) than those with iPET-nCMR (41 and 86%, respectively, P-value < 0.0001). In multivariable analyses, iPET retained an independent prognostic factor of EFS and OS (P-value < 0.0001 and P-value = 0.002, respectively). iPET is highly predictive of outcome of HL patients treated with ABVD and allows to tailor therapy to the individual patient.