Effectiveness of intravenous high-dose methotrexate for prevention of relapse in patients with DLBCL

e19562 Background: Central nervous system (CNS) relapse develops in 2-10% of patients with diffuse large B cell lymphoma (DLBCL) and has an adverse prognosis. Tools like IPI and CNS-IPI scores identify patients at high risk of systemic or CNS relapse based on the presence of established risk factors ( Schmitz et al. JCO 2016). International guidelines propose prophylactic intravenous high-dose methotrexate (HD-MTX) for patients at high risk of CNS relapse; however, limited data is backing this approach. Methods: We conducted a retrospective review of newly diagnosed DLBCL patients aged 18-75 years treated with curative intent at large academic medical centers in Riyadh, Saudi Arabia, between 2015-2018. Patients who were planned for CNS HD-MTX after cycles 2, 4, and 6 of R-CHOP and received at least one HD-MTX cycle were included. Results: We identified 35 DLBCL patients who received at least one R-CHOP cycle with one cycle of HD-MTX. The median IPI and CNS-IPI score were 3, (range = 0-4) and 3, (range = 0-5), respectively. The median number of R-CHOP cycles received was 6 (range 3-6) and HD-MTX 3 (range 1-6). The overall response rate was 91%, with 3 (9%) primary refractory patients per interim evaluation on cycle 3 of R-CHOP. Achieving complete remission after six cycles of RCHOP was noted in 80%, with four additional patients showed residual disease at the end of treatment evaluation. The entire cohort's overall survival was not reached, and five years estimated survival is 75%. With a median follow-up duration of 37.3 months, none of the patients relapsed after achieving CR at the end of treatment evaluation. The risk of systemic or CNS relapse in our cohort was 0%. In restricting the analysis to CNS-IPI of ≥ 4, a total of 13 patients with a median follow-up of 42 months were included; four patients did not achieve CR by the end of treatment, while nine patients continue to be in CR without any evidence of relapsed disease. Conclusions: High-dose methotrexate with high-intensity chemoimmunotherapy (R-CHOP) seems to be associated with an improvement in the expected rate of CNS relapse. Our data set is small, and a more extensive study evaluating HD-MTX's effectiveness in high-risk DLBCL is warranted.[Table: see text]