Value of interim FDG PET/CT for monitoring response to therapy and predicting prognosis in Hodgkin’s lymphoma treated with ABVD chemotherapy

Background: The goal of this study was to assess the interim FDG PET’s (iPET) predictive value in patients with Hodgkin’s lymphoma (HL) treated with ABVD chemotherapy.

Methods: We retrospectively searched our database between 31/12/2013 and 31/12/2017 for patients with de novo HL, treated with upfront ABVD, who had undergone baseline and iPET (after 2 or 4 ABVD cycles) and had at least 6 months of follow-up after therapy. The response assessment on iPETs was based on the Deauville scores (DS). Patients were classified as having a complete metabolic response (CMR, DS 1-3) and non-CMR (DS≥4). The response at the end of ABVD was assessed by FDG PET/CT and biopsy confirmation for patients with residual FDG uptake. The association between iPET and end of therapy response status was investigated using logistic regression analysis. Survival analysis was performed using the Cox regression hazard model and Kaplan-Meier methods.

Results: A total of 245 patients was included in the study. The median age of patients was 29 years (range, 18-83), and the follow-up time was 32 months (range, 6-81 months). Sixty-nine patients underwent iPET-2 and 176 iPET-4. There was no association between the timing of iPET and the iPET -response status (p=0.71). Among the total, 201 patients (82%) had iPET-CMR and 44 (18%) iPET-nCMR. iPET was strongly correlated with the end of therapy response status; 194/201 of iPET-CMR had CR and 29/44 of iPET-nCMR had no CR at the end of chemotherapy (p<0.0001). iPET-CMR patients had a better outcome with 91% 3-y EFS and 95% 3-y OS than patients with iPET-nCMR (41% 3-y EFS and 86% 3-y OS, p<0.0001 for both). In univariate analysis, the baseline risk factors such as patient age ≥45 and disease stage IV were statistically significant prognostic factors (p<0.05 for EFS and OS). In multivariate analysis, the disease stage remained independent only for EFS (p=0.006) and patient age for OS (p<0.0001) while iPET retained significance for EFS and OS (p<0.0001 and p=0.001, respectively).

Conclusions: Interim PET is highly predictive of the outcome of patients with HL treated with ABVD chemotherapy. iPET's early and accurate assessment of the response might help tailor therapy to the individual patient. Keywords: Hodgkin’s lymphoma, PET/CT, interim, prognosis.