Continuous intrathecal injection therapy of methotrexate is a therapeutic option in primary CNS lymphoma.

Primary central nervous system lymphoma (PCNSL) is a rare subtype of non-Hodgkin's lymphoma, and its prognosis is still very poor despite the conventional therapy of high-dose methotrexate (HD-MTX) followed by whole-brain radiation therapy (WBRT). The purpose of the present study was to evaluate the survival benefit of continuous intrathecal injection therapy of methotrexate (CIT-MTX) combined with the conventional therapy. A total of 26 PCNSL patients treated with CIT-MTX were analyzed. Ten mg of methotrexate were continuously injected into the lateral ventricle via a subcutaneous port over 5 days biweekly for 5 cycles. CIT-MTX was performed with WBRT in addition to HD-MTX in 15 cases, and 11 cases with high risk for HD-MTX were treated with CIT-MTX and WBRT. The response rate of all patients was 92.3%, and median progression-free survival and median overall survival (mOS) were 59.4 months and 93.8 months, respectively. Median OS of patients treated with CIT-MTX in addition to HD-MTX and WBRT was longer than the previously reported mOS with HD-MTX and WBRT (95 vs 33 months). In cases that could not tolerate HD-MTX, mOS of patients treated with CIT-MTX and WBRT was longer than the previously reported mOS with WBRT alone (36.7 vs 18 months). There was no difference in OS between patients with cerebrospinal fluid dissemination and patients without (p = 0.83). Better prognosis in patients treated with CIT-MTX may be derived from stable concentration of methotrexate in the cerebrospinal fluid. CIT-MTX was an effective additional therapeutic option for PCNSL.