JRSBRT 3.1, p. 37-42

Low-dose whole brain radiotherapy combined with radiosurgery for primary CNS lymphoma achieving partial response to induction methotrexate-based chemotherapy
Daniel S. Oh, James A. Vredenburgh, David A. Reardon, Leonard R. Prosnitz, Jon P. Gockerman, John H. Sampson, Christopher R. Kelsey and John P. Kirkpatrick

Purpose: For patients with primary CNS lymphoma who achieve complete response (CR) after induction methotrexate-based chemotherapy with rituximab, lowdose 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.

Keywords: Primary CNS lymphoma, radiosurgery, methotrexate, low dose whole brain RT, partial response, ritxuimab

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