Pilot study of gamma-knife surgery-incorporated systemic chemotherapy omitting whole brain radiotherapy for the treatment of elderly primary central nervous system lymphoma patients with poor prognostic scores

Systemic chemotherapy followed by whole brain radiotherapy (WBRT) is a widely used treatment strategy for patients with primary central nervous system lymphoma (PCNSL). However, the outcome of this treatment strategy in elderly patients, particularly with a poor prognostic score, was disappointing compared with younger patients, and the deterioration of cognitive function after WBRT is more problematic in these patients. To avoid this debilitating complication of WBRT and increase treatment efficacy in elderly patients, we designed systemic chemotherapy that incorporated interim gamma-knife surgery (GKS) treatment for elderly PCNSL patients (age ≥65 years), omitting WBRT in this pilot trial. A total of four elderly patients with a poor prognostic score based on an International Extranodal Lymphoma Study Group were enrolled in this pilot clinical trial. All study patients acquired complete response and showed stable or improved neuropsychological function during the disease-free state. The median progression-free survival was 9.5 months (range 8.6–22.5 months), and the median overall survival was 15.8 months (range 13.3–25.1 months), which were likely to be similar to those of the chemotherapy followed by WBRT for those patients. This pilot study demonstrated that GKS-incorporated systemic chemotherapy can obtain complete response with high probability and considerably long survival, which suggests that this treatment strategy is efficient and neuropsychologically safe for elderly PCNSL patients with a poor prognostic score.