Incidence of Central Nervous System Relapse in Primary Mediastinal Large B-Cell Lymphoma: Implications for Central Nervous System Prophylaxis

Background: Primary mediastinal large B-cell lymphoma (PMBCL) is an uncommon type of aggressive B-cell non-Hodgkin lymphoma. PMBCL shares some clinical and biologic features with nodular sclerosis classic Hodgkin lymphoma (cHL). Central nervous system (CNS) relapse is exceedingly rare in cHL. Therefore, it may be expected that CNS relapse in PMBCL is also uncommon. Herein, we examined the incidence of CNS relapse in patients with PMBCL treated with standard chemoimmunotherapy.

Patients and methods: This retrospective single center analysis included 154 patients with newly diagnosed PMBCL seen at Mayo Clinic. The CNS relapse rate was calculated using a competing risk model, with death considered as a competing risk.

Results: With a median follow-up of 39 months, 3 patients experienced CNS relapse, all associated with systemic relapse. The cumulative incidence of CNS relapse for the entire cohort was 1.43% (95% CI, 0.3%-4.6%) at 1 year and 2.21% (95% CI, 0.6%-5.8%) at both 2 and 5 years. For those who did not receive CNS prophylaxis (n = 131), the incidence was 0.85% (95% CI, 0.1%-4.2%) at 1 year and 1.80% (95% CI, 0.3%-5.8%) at both 2 and 5 years. All 3 patients who experienced CNS relapse had R-CHOP as frontline therapy; 2 patients did not receive any CNS prophylaxis, while 1 patient received intrathecal CNS prophylaxis.

Conclusion: The risk of CNS relapse in PMBCL appears to be very low after treatment with standard chemoimmunotherapy, suggesting routine CNS prophylaxis is not necessary.