Prognostic value of [¹⁸F]FDG PET/CT in patients with CNS lymphoma receiving ibrutinib-based therapies.

Abstract

Current clinical and imaging tools remain suboptimal for predicting treatment response and prognosis in CNS lymphomas. We investigated the prognostic value of baseline [¹⁸F]FDG PET in patients with CNS lymphoma receiving ibrutinib-based treatments. Fifty-three patients enrolled in a prospective clinical trial and underwent brain PET before receiving single-agent ibrutinib or ibrutinib in combination with methotrexate with or without rituximab. [¹⁸F]FDG uptake in these lesions was quantified by drawing PET volumes of interest around up to five [¹⁸F]FDG-avid lesions per patient (with uptake greater than surrounding brain). We measured standardized uptake values (SUV_max), metabolic tumor volumes, total lesion glycolysis (TLG), and the sum thereof in these lesions. We analyzed the relationship between PET parameters and mutation status, overall response rates, and progression-free survival (PFS). Thirty-eight patients underwent single-agent therapy and 15 received combination therapy. On PET, 15/53 patients had no measurable disease. In the other 38 patients, a total of 71 lesions were identified on PET. High-intensity [¹⁸F]FDG uptake and a larger volume of [¹⁸F]FDG-avid disease were inversely related to treatment outcome (p ≤ 0.005). In univariable analysis, PFS was linearly correlated with all PET parameters, with stronger association when sum-values were used. A multivariable model showed that risk of progression increased by 9% for every 5-unit increase in sumSUV_max (hazard ratio = 1.09 [95% CI: 1.04 to 1.14]). Higher lesional metabolic parameters are inversely related to outcome in patients undergoing ibrutinib-based therapies, and sumSUV_max emerged as a strong independent prognostic factor. NCT02315326; https://clinicaltrials.gov/ct2/show/NCT02315326?term=NCT02315326&draw=2&rank=1.