Low-dose Whole Brain Radiotherapy Combined with Radiosurgery for Primary CNS Lymphoma Achieving Partial Response to Induction Methotrexate-Based Chemotherapy.

PURPOSE:For patients with primary CNS lymphoma who achieve complete response (CR) after induction methotrexate-based chemotherapy with rituximab, low-dose whole brain radiation therapy (LD-WBRT) appears effective and is well tolerated. For patients who respond to induction methotrexate-based chemotherapy with or without rituximab but have unifocal residual disease less than 3 cm in size, we hypothesized that LD-WBRT combined with radiosurgery would be effective at controlling residual disease and well tolerated.METHODS:Four adult patients with primary CNS lymphoma with a favorable response to induction chemotherapy but had residual disease less than 3 cm were identified. Induction chemotherapy consisted of methotrexate with or without additional agents including rituximab. LD-WBRT comprised 2340 cGy in 13 fractions. This was immediately preceded or followed by a single radiosurgery treatment of 12 12.5 Gy to the focus of residual disease defined on contrast enhanced T1 weighted MRI.RESULTS:The median follow-up was 17.1 months (range 10-23 months). All patients had residual disease after induction chemotherapy but achieved complete response (CR) following LD-WBRT and radiosurgery. Three patients remained free of disease. One patient developed distant brain recurrence 12 months after radiation but remained alive at last follow-up (17 months). No treatment-related neurotoxicity was observed.CONCLUSIONS:The combination of induction methotrexate-based chemotherapy with or without rituximab, LD-WBRT and radiosurgery appears effective and well tolerated in patients with primary CNS lymphoma who achieve a partial response (PR) to chemotherapy with minimal residual disease. Longer follow-up and larger patient numbers are clearly needed for confirmation.