Purpose: To assess the effect of a reduced dose of radiotherapy (RT) in patients with primary CNS lymphoma (PCNSL) responding to the cyclophosphamide, doxorubicin, vincristine, and dexamethasone (CHOD)/carmustine, vincristine, methotrexate, and cytarabine (BVAM) regimen.
Patients and methods: Patients received one cycle of CHOD and two of BVAM. In the first trial, all 31 patients received 45-Gy whole-brain RT (CHOD/BVAM I). In the second, with 26 patients, RT dose was reduced to 30.6 Gy if there was a complete response (CR) after chemotherapy (CHOD/BVAM II).
Results: Age, performance status, and chemotherapy received were similar in both protocols. CR rate at the end of all treatment was 68% for CHOD/BVAM I and 77% and for CHOD/BVAM II. Treatment modality was the only predictor of relapse, with 3-year relapse risks of 29% and 70% for CHOD/BVAM I and II, respectively. This was specifically important in the 25 patients less than 60 years old (3-year relapse risk, 25% v 83%; P =.01). The 5-year overall survival (OS) was 36%. Age (< 60 v > or = 60 years) was the only predictor for OS in the multivariate analysis (relative risk, 2.1; 95% confidence interval, 1.4 to 2.8). RT dose was the only predictor of OS in patients younger than 60 years old who achieved CR at the end of all treatment (3-year OS, 92% v 60% for patients receiving 45 or 30.6 Gy, respectively; P =.04).
Conclusion: Reduction of the RT dose from 45 Gy to 30.6 Gy in patients younger than 60 years old with PCNSL who achieved CR resulted in an increased risk of relapse and lower OS.