ASSESSING THE EFFICACY AND TOXICITY OF CNS PROPHYLAXIS IN DIFFUSE LARGE B-CELL LYMPHOMA (CLSG-CNS-01): A RANDOMIZED, MULTICENTER, PROSPECTIVE PHASE 3 TRIAL

Abstract

Introduction: CNS relapse occurs in around 5% of patients with systemic diffuse large B-cell lymphoma (DLBCL) and its prognosis is poor. The optimal strategy for CNS prophylaxis is not established. The CLSG-CNS-01 trial compared CNS prophylaxis with high doses of intravenous (i.v.) methotrexate (MTX) and intrathecal (i.t.) MTX in systemic DLBCL.

Methods: This randomized, multicenter, prospective phase 3 trial was registered at ClinicalTrials.gov (NCT02777736). Patients with systemic DLBCL aged between 18 and 72 years were treated with 6 cycles of R-CHOP+2xR or DA EPOCH-R+2xR. Patients with intermediate (2–3 risk factors) and high risk (4–6 risk factors) for CNS relapse were randomly assigned (1:1) to CNS prophylaxis with either 2 doses of MTX 3g/m² i.v. (arm A) or 6 doses of MTX 12 mg i.t. (arm B). Low risk patients (0–1 risk factor) for CNS relapse were not randomized and did not receive CNS prophylaxis (arm C). Primary objective was to compare cumulative incidence of CNS relapse between arms A and B. Major secondary objectives included: overall response rate (ORR), progression-free and overall survivals (PFS, OS) and treatment toxicity.

Results: Overall 100 patients were enrolled between 2015 and 2024: 30 were randomly assigned to arm A and 31 to arm B; 39 patients did not receive prophylaxis (arm C). Median age of patients was 61 years (range 27–72) and 54% were male. CNS relapses occurred in 3 (3%) patients (arm A 1, arm B 2) during the median follow-up of 54.9 months. CNS relapse after MTX i.v. occurred later (5.2 years after the initiation of treatment). Comparison of 5year cumulative incidence of CNS relapse between randomized arms A and B did not reach statistical significance (0% vs. 8.7%, HR 1.521, p = 0.72). ORR was not significant among arms A, B, C (83.3% vs. 83.8% vs. 94.8%, p = 0.20). The 5year PFS was comparable in arms A and B (45.3% and 57.4%), HR 0.66, p = 0.20. CNS prophylaxis (i.v. and i.t.) significantly increased neutropenia grade ≥ 3 (12.61% vs. 18.48 % vs. 3.59 %, p < 0.0001) with the highest rate of infections grade ≥ 3 in arm A (4.95% vs. 0.95% vs. 0.80%, p = 0.0046). Other toxicities grade ≥ 3 occurred most frequently in arm A (p = 0.0039). Overall 29 patients died (arm A 16, arm B 10, arm C 3). Infections (arm A 5 vs. arm B 2) and unknown causes (arm A 4 vs. arm B 2) indicated the major difference between randomized arms. This observation resulted in significantly worse 5year OS in arm A versus B (47.2% vs. 72.4%, HR 0.46, p = 0.04).

Conclusions: CNS prophylaxis with MTX i.v. or i.t. did not eliminate CNS relapse, but MTX i.v. delayed its occurrence. Cumulative incidence of CNS relapse did not differ significantly between i.v. and i.t. MTX prophylaxis, however, the number of randomized patients was low. MTX i.v. was significantly associated with worse OS, probably due to the toxicity.

Research funding declaration: This work was supported by grant AZV NU21-03-00411 from the Ministry of Health of the Czech Republic and by the Cooperation Program, research area “Oncology and Haematology”

Keywords: chemotherapy; aggressive B-cell non-Hodgkin lymphoma

No potential sources of conflict of interest.