Pemetrexed plus rituximab as second-line treatment for primary central nervous system lymphoma

The aim of the study was to determine the efficacy and toxicity of pemetrexed plus rituximab in patients with primary central nervous system lymphoma, who had undergone treatment with high-dose (HD) methotrexate-based regimens. Patients who had failed HD methotrexate-based regimens treatment had ECOG performance status ranging from 0 to 2. Twenty-seven patients received pemetrexed plus rituximab as second-line treatment. Rituximab 375 mg/m² was administered on day 0 and pemetrexed 500 mg/m² was administered on day 1 every 3 weeks. Six patients (22.2 %) experienced CR, 11 patients (40.7 %) had PR, eight patients (29.6 %) had SD, and two patients had PD. The response rate was 62.9 %. The median time to progression (PFS) was 6.9 months (95 % CI, 5.6–8.3), and the median overall survival was 11.2 months (95 % CI, 9.1–13.4). In the subgroup analysis, PFS had a significant difference among the low level of serum miR-21 and high level of serum miR-21. PFS was 9.0 (95 % CI, 6.3–11.6) and 5.7 months (95 % CI, 4.6–6.9, log rank = 0.015), respectively. None of the patient experienced grade 4 toxicity. A regimen of pemetrexed combined with rituximab is marginally effective and well tolerated in patients with PCNSL who had failed HD methotrexate-based regimens first-line treatment.