Radiation-Sparing Treatment of HIV-Related Primary Central Nervous System Lymphoma with Antiretroviral Therapy, Rituximab and High-Dose Methotrexate

BACKGROUND: HIV-associated primary central nervous system lymphoma (HIV-PCNSL) is an AIDS-defining cancer. Tumors occur in patients with very low CD4⁺ counts, and tumors are almost always Epstein-Barr virus (EBV) infected. Overall survival (OS) has improved over time with antiretroviral therapy (ART)-associated immune reconstitution but is still generally less than 1 year. Treatment has traditionally included whole brain radiation, which can lead to devastating long-term neurotoxicity, including cognitive decline. ART has made it possible to treat patients with curative-intent, but radiation-sparing approaches have not been studied prospectively in HIV-PCNSL.

METHODS: In a prospective phase II pilot study conducted in the HIV & AIDS Malignancy Branch at the National Cancer Institute, we evaluated curative-intent radiation-sparing immunochemotherapy in patients with untreated HIV-PCNSL (NCT00267865). Patients with HIV-PCNSL received ART, rituximab (375 mg/m²) and HD-MTX (6 g/m²) with leucovorin rescue (R-HD-MTX). Responses were evaluated by modified International Working Group Response Criteria for PCNSL after 6 cycles of induction R-HD-MTX and patients with a complete response (CR) received 2 consolidation cycles of R-HD-MTX. Patients with poor renal or cardiac function who were not eligible to receive HD-MTX at enrollment, received ART, rituximab and best-available radiation-sparing care. The primary objective of the study was to estimate the percentage of patients receiving ART and R-HD-MTX alive without recurrent lymphoma at two years. Response to treatment, immune reconstitution, and OS were evaluated using descriptive statistics and Kaplan-Meier methodology.

RESULTS: Twelve patients were enrolled between September 2006 and June 2016. One enrolled patient was initially ineligible to receive HD-MTX due to renal dysfunction and received rituximab with temozolomide (TMZ) 150 mg/m² for 5 days for one cycle followed by 6 cycles of R-HD-MTX + TMZ and 2 consolidation cycles of R-HD-MTX. Patient characteristics: 9 men, 3 women; median (med) age 33 years (range: 21-55); 8 African-American, 3 Hispanic, 1 white non-Hispanic; med Eastern Cooperative Oncology Group performance status 2 (1-3); med baseline Mini Mental State Examination (MMSE, maximum score = 30) was 22 (range: 5-29). Only 4 patients were on ART prior to diagnosis, and all but 1 had been on ART less than 4 months. Med time from HIV infection to PCNSL diagnosis was 30 weeks (range: 0-23 years). Med CD4⁺ T-cell count at PCNSL diagnosis was 16 cells/µL (0-409). Diagnosis of PCNSL was biopsy-confirmed (11) or made by ¹⁸fludeoxyglucose positron emission tomography/cerebral spinal fluid (CSF) EBV viral load criteria (1). 11/12 tumors were EBV positive. Flow cytometry showed leptomeningeal disease in 4 patients. Three had concurrent CNS infections, including Cryptococcus, histoplasmosis, and CMV retinitis. Ten were evaluable for response to R-HD-MTX induction. Two patients received only 1 cycle of therapy and were not evaluable due to treatment failure (TF). Responses after R-HD-MTX induction: CR (5), partial response (PR) (4) and progressive disease (PD) (1). Two patients with a PR received second-line TMZ at end of R-HD-MTX and obtained a subsequent CR. The patient with PD received second-line therapy with the Cancer and Leukemia Group B 50202 induction regimen and obtained a subsequent CR. There were 4 deaths on study: 1 pulmonary embolism, 1 CNS fungal infection in setting of PD, 2 TF. Eight patients (67%), including 3 patients who received second line therapy, obtained a durable CR. Med CD4⁺ T-cell increase following R-HD-MTX induction was +35 cells/uL (range: -54 - +369). In surviving patients, med MMSE after R-HD-MTX was 28 (27-30). For all patients, estimated 60-month OS was 66% (95% CI: 32-86%) with med potential follow-up of 82 months. Med OS was not reached.

CONCLUSIONS:Treatment with ART and R-HD-MTX is associated with a high response rate, CD4⁺ immune reconstitution, preserved cognition, and improved OS, even in a high-risk patient population.