Effectiveness and limitation of gamma knife radiosurgery for relapsed central nervous system lymphoma: a retrospective analysis in one institution.

We describe 6 patients with relapsed central nervous system lymphoma (CNSL) treated with Gamma Knife radiosurgery (GKR). The histologic diagnosis in all 6 patients was diffuse large B-cell lymphoma without human immunodeficiency virus infection. Two patients had intracranial relapse of primary CNSL, and the remaining 4 had CNS relapse of systemic lymphoma. All patients were treated with GKR without severe adverse effects, and all but 1 patient received subsequent chemotherapy shortly after GKR. Four patients showed a complete response, and the remaining 2 patients had a partial response or stable disease. Although the neurologic symptoms disappeared or improved markedly in all patients, all of the diseases recurred or progressed 3 to 13 months after the first GKR. A second GKR was eventually performed in 4 patients. The median overall survival and progression-free survival times after the first GKR were 17 and 11 months, respectively. In our experience, GKR seems to be a useful procedure for the treatment of relapsed CNSL, because it facilitates excellent local control in a short-term treatment period without severe complications, although the efficacy period is not long enough.