An interim positron emission tomography (PET) scan after four treatment cycles emerged as the strongest predictor of outcomes for primary mediastinal B-cell lymphoma (PMBL) patients, according to a study published in Blood Advances.
The post-hoc analysis aimed to detail the outcomes of PMBL patients in the GAINED study, a randomized phase 3 trial in Belgium and France comparing obinutuzumab to rituximab plus ACVBP or CHOP14 induction, followed by PET-guided consolidation. Patient outcomes were verified through expert pathological review and the use of gene-expression profiling and next-generation sequencing.
Of the centrally reviewed 620 patients, 138 (22.3%) confirmed PMBL cases were analyzed by the investigators. Patients had a median age of 33.5 years; 63.8% were female. Disease characteristics included 55.1% with stage III-IV disease, 90.6% with elevated LDH, 87.6% with ECOG 0-1, 62.3% with extranodal involvement, 52.6% with aaIPI 2-3, and 53.6% with bulky disease (mediastinal mass >10 cm).
Key somatic mutations in 87 patients including the following: SOCS1 (70.1%), B2M (56.3%), STAT6 (49.4%), TNFAIP3 (47.1%), GNA13 (39.1%), CIITA (37.9%), CD58 (36.8%), and TP53 (29.9%).
Post-induction treatments, based on interim PET results obtained after two cycles and again after four cycles of treatment, included standard consolidation chemotherapy, intensive treatment and autologous transplantation, and salvage therapy.
The results showed favorable outcomes with dose-dense induction and PET-driven consolidation, with two-year progression-free survival and overall survival rates of 86.2% and 93.2%, respectively after a median follow-up of 39.5 months.
Notably, a response of ΔSUVmax ≤70% in the interim PET results after four cycles of treatment emerged as the strongest dynamic predictor of shorter progression-free survival (HR 6.6; P= 0.0004), regardless of the treatment group, the investigators reported.
These findings suggest that interim PET results after four cycles of treatment are a robust prognostic factor for identifying high-risk PMBL patients, according to the authors.
Reference
Camus V, Molina TJ, Desmots F, et al. Interim PET after 4 Cycles Predicts Outcome in Histomolecularly Confirmed Primary Mediastinal B-Cell Lymphoma. Blood Adv. 2025. doi:10.1182/bloodadvances.2024015577
