Whole brain radiotherapy improves survival outcomes in primary CNS lymphoma patients ineligible for systemic therapy.

Primary central nervous system lymphoma (PCNSL) is a very rare type of malignancy with a poor prognosis. The role of whole brain radiotherapy (WBRT) in PCNSL has been questioned due to the significant neurotoxicity and lack of convincing data for survival benefit. Even its role in a palliative setting remains to be clearly elucidated. Our study aims to investigate the benefit of WBRT in patients who are ineligible for systemic therapy. A single-institution retrospective study was conducted on patients diagnosed with PCNSL between 2002 and 2017. Patients were excluded if they received systemic therapy or focal radiation only. Data on patient demographics and WBRT were collected and correlated with clinical outcomes. A total of 48 patients were selected for analysis, among which 31 (64.6%) patients received WBRT and 17 (35.4%) patients received supportive care only. Patient baseline characteristics were similar between the two groups. Median overall survival (OS) was 4.3 months among the entire cohort. WBRT was associated with improved median OS (8.0 months, range 1.4–62.3 months) compared with supportive care only (3.3 months, range 0.7–18.3 months) (HR 0.39, 95% CI 0.20–0.75, p = 0.005). Among patients who received WBRT, higher radiation dose to the whole brain was not associated with survival (p = 0.10), but higher radiation dose to the gross tumor was associated with improved survival (p = 0.007). Patients with PCNSL who are ineligible for systemic therapy may still benefit from WBRT with improvement in survival, compared with the best supportive care. Dose escalation through the addition of a gross tumor boost in these patients was associated with improved overall survival. Further studies in the prospective setting are necessary to confirm the findings from the study.