High-Dose Methotrexate, Rituximab, and Temozolomide (MRT) for Patients with Primary CNS Lymphoma (PCNSL).

PCNSL is a rare form of non-Hodgkin lymphoma. High-dose methotrexate (HD-MTX) is the backbone of therapy but uncertainty remains about what additional chemotherapies should be added to HD-MTX to improve response rates.After receiving IRB consent, we retrospectively evaluated patients with PCNSL treated at our hospital with combination M/R/T at initial diagnosis or at relapse. Patients were treated in 28-day induction cycles as follows: HD-MTX (8g/m2- dose adjusted based on creatinine clearance) on days 1 and 15; rituximab (375 mg/m2) on days 3, 10, 17, and 24; and temozolomide (150-200 mg/m2) on days 7-11. HD-MTX was given every 2 weeks until complete response (CR) and for 2 additional treatments followed by monthly maintenance treatments for 11 months. Rituximab was given weekly for a total of 8 weeks. Temozolomide was continued for 6 months after CR. Brain MRI was done after every other methotrexate treatment to assess response.Sixteen patients were treated between February 2006 and August 2009. Ten patients received MRT as first-line therapy at the time of initial diagnosis and 6 received MRT as salvage therapy at first or second recurrence. The median age of newly diagnosed patients was 58 (range 47-76) and of relapsed patients was 60 (range 46-76). CSF cytology was atypical in 5/15 patients who underwent lumbar puncture (4 first-line, 1 relapse). After first-line therapy, there were 9 CRs (median cycles to CR = 3) and 1 PR (patient still receiving induction treatment). After salvage therapy, there were 4 CRs (median cycles to CR = 4) and 2 PRs (both patients died while receiving treatment- 1 from an unrelated myocardial infarction). With a median follow-up of 10.3 months in the first-line group and 7.2 months in the relapse group, only 3 patients have progressed; one of whom had clinical progression after a PR and a second who relapsed in the skin. Treatment was well tolerated with reversible grade 4 transammonitis in 1 patient and grade 3 hematological toxicities in 8 patients. One patient experienced grade 4 thrombocytopenia related to temozolomide requiring dose reduction for subsequent cycles.Combination MRT is well tolerated and resulted in a promising early response rate. The median number of cycles needed to achieve a CR for patients with newly diagnosed PCNSL was less than the 6 cycles we have previously reported for HD-MTX monotherapy suggesting that adding rituximab and temozolomide is beneficial to patients. This combination warrants further evaluation in larger scale, prospective studies.Off Label Use: temozolomide and rituximab for PCNSL..