Background: The most common aggressive lymphoma in adults is diffuse large B-cell lymphoma (DLBCL). Consolidative radiotherapy (RT) is often administered to DLBCL patients but guidelines remain unclear, which could lead to unnecessary RT. We aimed to evaluate the value of end-of-treatment PET-CT scans, interpreted using the Deauville score (DV), to guide the utilization of consolidative RT, which may help spare low-risk DLBCL patients from unnecessary RT.
Methods: We included all DLBCL patients diagnosed between 2010 and 2022 at the National Cancer Centre Singapore with DV measured at the end of the first-line chemoimmunotherapy. The outcome measure was time-to-progression (TTP). The predictive value of DV for RT was assessed based on the interaction effect between the receipt of RT and DV in Cox regression models.
Results: The data of 349 patients were analyzed. The median follow-up time was 38.1 months (interquartile range 34.0-42.3 months). RT was associated with a significant improvement in TTP amongst the DV4-5 patients (HR 0.33; 95%CI 0.13-0.88; p = 0.027) but not the DV1-3 patients (HR 0.85; 95%CI 0.40-1.81; p = 0.671) (interaction's p = 0.133). Multivariable analysis reported that RT was again significantly associated with improved TTP among the DV4-5 patients (adjusted HR 0.29; 95%CI 0.10-0.80; p = 0.017) but not the DV1-3 group (HR 0.86; 95%CI 0.40-1.86; p = 0.707) (interaction's p = 0.087).
Conclusion: Our results suggests that DLBCL patients with end-of-treatment PET-CT DV1-3 may not need consolidative RT. Longer follow-up and prospective randomized trials are still necessary to investigate long-term outcomes.
Keywords: DLBCL; PET-CT; consolidative treatment; de-escalation; radiotherapy.