Prognostic assessment of primary central nervous system lymphoma: Potential utility of Thallium-201 SPECT

487 Objectives: Primary central nervous system lymphoma (PCNSL) is rare, but its incidence is rapidly increasing. PCNSL is initially radiosensitive, but unfortunately its remission is short-lived, resulted in poor overall survival. Although radiological imaging findings of PCNSL have been well described, the significances of these findings in the prediction of patient’s prognosis have not been elucidated enough. The purpose of this study was to investigate the potential utility of imaging findings as predictor of prognosis in PCNSL. Methods: From January 1983 to December 2004, 48 patients with PCNSL treated by radiation therapy were included. On MRI, tumor characteristics (tumor size, number of lesions, degree of edema) were evaluated, and the initial response was classified into complete response (CR), partial response (PR), no change (NC) and progressive disease (PD). Thallium-201 (201Tl) SPECT were obtained at 10 minutes after 111 MBq of 201Tl injection, and the radioactivity ratios of tumors to normal brain (T/N ratios) were calculated. We retrospectively investigated the relationship of patient prognosis to the following clinical variables and imaging findings: patient age, gender, performance status (PS), total radiation dose, initial response, tumor size, number of lesions, degree of edema, and T/N ratio. The survival data were analyzed using the Kaplan-Meyer methods and compared using the log-rank test. Results: For all 48 patients, the median survival time was 20 months and the survival rates were 35% at 2 years and 18% at 5 years. Patients with younger age ( Conclusions: In PCNSL, MRI is useful to evaluate tumor extent and initial treatment response, however it has limitations to predict prognosis. 201Tl-SPECT has potential utility to predict prognosis, and it would be recommended in future protocol design of PCNSL.