Timing of high-dose methotrexate CNS prophylaxis in DLBCL: an analysis of toxicity and impact on R-CHOP delivery.

High-dose methotrexate (HD-MTX) is increasingly used as prophylaxis for patients with diffuse large B-cell lymphoma (DLBCL) at high risk of central nervous system (CNS) relapse. However, there is limited evidence to guide whether to intercalate HD-MTX (i-HD-MTX) between R-CHOP-21 (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone given at 21-day intervals) or to give it at the end of treatment (EOT) with R-CHOP-21. We conducted a retrospective, multicenter analysis of 334 patients with DLBCL who received CNS prophylaxis with i-HD-MTX (n = 204) or EOT HD-MTX (n = 130). Primary end points were R-CHOP delay rates and HD-MTX toxicity. Secondary end points were CNS relapse rate, progression-free survival, and overall survival. The EOT group had more patients with a high CNS international prognostic index (58% vs 39%; P < .001) and more concurrent intrathecal prophylaxis (56% vs 34%; P < .001). Of the 409 cycles of i-HD-MTX given, 82 (20%) were associated with a delay of next R-CHOP (median, 7 days). Delays were significantly increased when i-HD-MTX was given after day 9 post-R-CHOP (26% vs 16%; P = .01). On multivariable analysis, i-HD-MTX was independently associated with increased R-CHOP delays. Increased mucositis, febrile neutropenia, and longer median inpatient stay were recorded with i-HD-MTX delivery. Three-year cumulative CNS relapse incidence was 5.9%, with no differences between groups. There was no difference in survival between groups. We report increased toxicity and R-CHOP delay with i-HD-MTX compared with EOT delivery but no difference in CNS relapse or survival. Decisions on HD-MTX timing should be individualized and, where i-HD-MTX is favored, we recommend scheduling before day 10 of R-CHOP cycles.