Lack of Influence of Rituximab and CNS Directed Prophylactic Therapy on CNS Relapse in High-Risk Diffuse Large B Cell Lymphoma

Background/method: Central nervous system (CNS) relapse in patients with diffuse large B-cell lymphoma (DLBCL) although uncommon, can be devastating. Conflicting reports have been published regarding the reduction in incidence of CNS relapse in post-rituximabera.We retrospectively identified all the patients with DLBCL who has received rituximab-based chemotherapy at initial presentation in our institute between 2004 and 2014. Patients were divided into two groups, ‘high risk’ group and ‘standard risk’ group, based on following definition. High risk group will have at least one of the following risk factors 1) LDH ≥ 650 U/L 2) Age adjusted International Prognostic Index (IPI) of ≥ 4 3) Involvement of > 1 extra nodal site 4) Involvement of testis 5) Breast 6) Bones 7) Kidneys 8) Adrenal glands 9) Retroperitoneal lymph nodes 10) Para-meninges or 11) Bone marrow. Patients without any of these risk factors were deemed standard risk. Descriptive statistics were used to analyze the incidence of CNS relapse, patient and disease characteristics. Historically reported incidence rates were used for comparison.

Results:One hundred and forty two consecutive patients with DLBCL were included in our study. One hundred and twenty two patients received rituximab-based therapy at the initial diagnosis. Forty-nine patients (40%) met the criteria for ‘high risk’ based on the above definition. Seventy-three patients (60%) qualified for standard risk group. Standard risk group received no CNS directed prophylaxis and none of these patients had CNS relapses. Thirty-one of 49 ‘high risk’ patients received CNS prophylaxis, mainly intrathecal methotrexate. Total 5 patients (4.09%) developed CNS relapse. CNS relapse in high-risk group was 10.2% (5/49). Median age at diagnosis in patients with CNS relapse was 53 years. Median time to relapse was 8.76 months. Median survival after the CNS relapse was 9.16 months. Four out of 5 patients received CNS prophylaxis with intrathecal methotrexate or systemic methotrexate or systemic cytarabine or a combination of them. Average number of doses of prophylaxis received by each patient was 3.2 (range 1-7). Only one patient who developed CNS relapse did not receive any CNS directed therapy as prophylaxis.

Conclusion:No significant reduction in the incidence of CNS relapse was noted with upfront use of rituximab. Our study confirms that majority of the DLBCL patients do not need CNS directed therapy. For high risk DLBCL patients, we not only need to develop better predictive markers for CNS relapse but also need better CNS directed therapies to prevent this fatal complication of highly curable disease.