Prognostic impact of procarbazine in R-MPV followed by reduced-dose whole-brain radiotherapy and cytarabine for primary central nervous system lymphoma

The R-MPV regimen-comprising rituximab, methotrexate, procarbazine (PCZ), and vincristine-followed by reduced-dose whole-brain radiotherapy and high-dose cytarabine, is an established treatment for primary central nervous system lymphoma (PCNSL). However, PCZ is occasionally omitted due to adverse events, and its prognostic impact remains unclear. Among 91 patients with PCNSL treated at our institution between 2008 and 2020, we analyzed 60 adults who completed the R-MPV regimen. The 5-year progression-free survival (PFS) rate for the entire cohort was 67.6%. PCZ was discontinued in 17 of the 60 patients. The 5-year PFS rate was significantly higher in patients who completed PCZ compared with those who discontinued it (81.2% vs. 46.3%; <i>p</i> = 0.00487). PCZ discontinuation was associated with inferior PFS in both univariable and multivariable analyses. These findings suggest that maintaining the full PCZ dose during R-MPV treatment may be critical for achieving favorable survival outcomes in patients with PCNSL.