AbstractThe optimal timing for administering high-dose methotrexate (HDMTX) when combined with (R)CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone, with/without rituximab) is unclear. Recent data showed that the administration of prophylactic HDMTX before day 10 of R- CHOP may lead to fewer treatment delays. Herein, we report our experience with HDMTX administered on day 1 of (R)CHOP in patients with aggressive non-Hodgkin lymphoma (NHL). We identified 140 patients treated with ≥1 cycle of HDMTX combined with (R)CHOP for prophylaxis against (n = 84) or treatment of (n = 56) central nervous system (CNS) involvement. Overall, (R)CHOP treatment delays ≥7 days (4% of cycles, 13% of patients), doxorubicin, and/or cyclophosphamide dose reductions (1% of cycles, 6% of patients) or (R)CHOP discontinuations due to toxicity (4% of patients) were uncommon. Neutropenic fever (NF) occurred in 7% of cycles and 24% of patients and was more common during HDMTX-containing cycles. Acute kidney injury (AKI) occurred in 19% of cycles but was mostly grade ≤2. Grade ≥3 hepatotoxicity and mucositis were uncommon (each 2% of cycles). In the prophylaxis cohort, the rates of NF and grade ≥2 AKI were lower in patients who initiated HDMTX with cycle 2 or later (11% vs 30%, P = .03 and 16% vs 39%, P = .03, respectively). Our data show that HDMTX administration on day 1 of (R)CHOP may improve the deliverability of (R)CHOP and the overall safety of the regimen compared with historical data of HDMTX administration on day 10 or later of R-CHOP. Delaying prophylactic HDMTX beyond cycle 1 of (R)CHOP may reduce the risk of NF and AKI.