PET4 Response As an Independent Predictor of Long-Term Outcomes in ECHELON2 (A+CHP Vs. CHOP) in CD30+PTCL

Background: Peripheral T-cell lymphomas (PTCLs) are uncommon, heterogeneous, and often aggressive subtypes of lymphoma characterized by a high risk of progression even after combination chemotherapy. The phase III, ECHELON-2 trial showed that the combination of brentuximab vedotin with chemotherapy (A+CHP) in patients (pts) with CD30-positive PTCLs improved progression-free survival (PFS) and overall survival (OS) compared to CHOP. In PTCL, positron emission tomography (PET) is a valuable way to assess disease burden and stage at the time of diagnosis and evaluate treatment response. Prior retrospective studies have shown that interim and end of treatment PET may predict outcomes; however, there are no prospective studies confirming their predictive value. In the ECHELON-2 study, PET4 outcomes were prospectively collected, and the objective of this exploratory analysis is to investigate the potential for interim PET scans to predict treatment response and long-term outcomes. Objective: To evaluate the role of interim 18F-FDG PET imaging (PET4) in predicting end of treatment (EOT) response, progression free survival (PFS), and overall survival (OS) in pts (pts) with CD30+PTCL treated with A+CHP or CHOP in the ECHELON-2 trial. Methods: The ECHELON-2 trial included prospective 18F-FDG PET scans and assessment of treatment response including long-term PFS per investigator and OS. PET4 status was based on Deauville score by Independent Review Facility (IRF) assessment using scans at the cycle 4 response assessment. Deauville scores 1-3 are considered negative (PET4neg) and 4-5 positive (PET4pos). EOT response is the best response after completion of study treatment and prior to long term follow up per Cheson 2007 by IRF assessment. Kaplan-Meier methods were used to estimate PFS and OS; p-values are based on stratified log-rank tests. All analyses are exploratory, and p-values are descriptive. Results: In this study, 452 pts were included, with 226 randomized to the A+CHP treatment arm and 226 to the CHOP treatment arm; median follow up was 66.8 months (range 0-90). Of randomized pts, 32 pts in the A+CHP arm and 41 pts in the CHOP arm were not evaluable for PET4. The overall results showed that the PET4neg evaluable subgroup had a higher proportion of pts achieving complete responses (CR) than PET4pos (80% vs. 9%) at EOT (Table 1). In pts assessed for PET4, pts who were PET4neg had improved PFS and OS in both the A+CHP and CHOP treatment arms (Figure 1). For A+C