Comparison of different response evaluation criteria in interim PET/CT for diffuse large B-cell lymphoma: is Δtotal metabolic tumor volume a worthwhile measure?

[OBJECTIVE] This study aimed to evaluate the most reliable predictors of progression-free survival (PFS) and overall survival (OS) among six different response criteria during interim PET (I-PET)/computed tomography (CT), including the change in total metabolic tumor volume (ΔTMTV) in patients with diffuse large B-cell lymphoma (DLBCL).

[METHODS] A retrospective analysis was conducted on patients with DLBCL who underwent baseline PET/CT and I-PET after 3-4 cycles of chemoimmunotherapy. Various response criteria were assessed, including Lugano, response evaluation criteria in lymphoma (RECIL), change in maximum standardized uptake value (ΔSUV max ), Peking, quantitative PET, and the novel ΔTMTV. Survival outcomes were obtained using Kaplan-Meier survival analysis and Cox proportional-hazards regression models and compared with Harrell's C-index for predictive accuracy.

[RESULTS] One hundred and two patients enrolled. The median PFS was 58 months, and the median OS was 63.5 months. ΔSUV max (cut-off: 66%) had the highest predictive accuracy for both PFS and OS (C-index: 0.689, 0.686; P  < 0.001). ΔTMTV (cut-off: 85.69%) was significantly associated with survival ( P  = 0.003 for PFS, P  = 0.005 for OS) but did not outperform other response criteria. RECIL showed better survival prediction when minor responders were categorized as stable disease rather than partial response. A high baseline TMTV (>126.8 cm³) was correlated with lower survival, as indicated by PFS ( P  = 0.004) and OS ( P  = 0.019).

[CONCLUSION] Interim PET/CT response evaluation using ΔSUV max66 is the most reliable predictor of survival in DLBCL. ΔTMTV has potential but requires improvement to enhance its prognostic accuracy. Future studies should explore refined segmentation methods to enhance metabolic tumor volume assessment in clinical practice.