RARE-49. DEFINING RELAPSE PATTERNS IN PRIMARY CNS DIFFUSE LARGE B-CELL LYMPHOMA: A MULTICENTER STUDY

The objective of this study was to describe relapse patterns in patients with primary CNS diffuse large B-cell lymphoma (DLBCL). Primary CNS lymphoma is a rare, malignant extra-nodal lymphoma confined to the brain, spinal cord, leptomeninges, and eyes. It accounts for less than 3% of primary brain tumors; over 90% are histologically DLBCL. Survival is inferior to other forms of extra-nodal DLBCL with relapse rates of > 50%, historically within two years of diagnosis. Post-remission surveillance is currently based on consensus opinion, and a better understanding of relapse patterns is required to determine optimal surveillance. We conducted a retrospective analysis of patients with primary CNS DLBCL seen at three tertiary hospitals. Survival estimates were calculated using the Kaplan-Meier method. A total of 172 immunocompetent patients with primary CNS DLBCL achieved radiographic CR to induction therapy. Median age at diagnosis was 62.6 years, with median Karnofsky Performance Score at diagnosis of 80. Initial treatment consisted of high dose methotrexate-based polychemotherapy in 53.4%, radiation therapy in 13.4% and intrathecal chemotherapy in 10.5%. 14% underwent stem cell transplantation. The relapse rate was 57% at a median interval of 2.9 years from diagnosis. Method of relapse detection was clinical in 49%, radiographic in 39%, and combined in 11.2%. The first relapse occurred at a remote CNS site in the majority of patients (57%). The 2, 5, and 10-year progression-free survival proportions were 74.8%, 45.6%, and 23.8%, respectively. We found that late and systemic relapse were more common than previously reported. Only half of the relapses were detectable clinically by symptoms. These results support current consensus guidelines of clinical and radiographic surveillance up to 10 years after diagnosis.