A Phase II Study of the Efficacy and Safety of the Srmt (Sintilimab, Rituximab, Methotrexate, and Temozolomide) Regimen in Newly Diagnosed Primary Central Nervous System Lymphoma

BACKGROUND

Primary central nervous system lymphoma (PCNSL) is a rare and aggressive subtype of lymphoma with poor prognosis. One potential therapeutic approach could involve targeting the programmed death-1 (PD-1) immune checkpoint pathway, as these tumors often express PD-L1. However, the efficacy of this strategy using sintilimab in combination with immunochemotherapy as frontline therapy for patients with newly diagnosed PCNSL remains uncertain.

METHODS

In this phase II trial with a safety run-in, we enrolled treatment-naive PCNSL patients between the ages of 18 and 70, who had an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. All patients were given sintilimab combined with rituximab, high-dose methotrexate and temozolomide (SRMT) regimen (six cycles every 21 days): sintilimab (200 mg, i.v., Day-0), rituximab (375 mg/m ², i.v., Day-0), methotrexate (3.0 g/m ², i.v., Day-1 or 1.0 g/m ² for patients aged ≥65 years, and temozolamide (150 mg/m ²/d, p.o., Days 1-5). The primary outcome was overall response rate (ORR), with secondary outcomes including duration of response (DOR), progression-free survival (PFS), overall survival (OS), safety, and potential biomarkers.

RESULTS

Between 3 April 2020 and 23 August 2022, a total of 28 patients were enrolled. No dose-limiting toxicities were observed during the safety run-in period. Among 27 evaluable patients, the primary outcome was met with an impressive ORR of 96.3% (95% CI: 81-99.9%). In detail, 25 patients (92.6%) achieved a complete response and one (3.7%) exhibited a partial response. As of 7 April 2023, the median follow-up was 20.8 months. The Medians for DOR, PFS, and OS were not reached. Remarkably, 2-year PFS and 2-year OS were 65.4% (48.1-88.8%) and 88.5% (74.1-100%), respectively. The most common grade 3-4 treatment-related toxicities were increased levels of alanine aminotransferase (18.5%) and aspartate aminotransferase (14.8%). Additionally, the receiver operating characteristic analysis revealed that the baseline IL10/IL6 ratio in cerebrospinal fluid exhibited promising performance in predicting PFS, achieving an area under curve of 0.91 at 2 years.

CONCLUSIONS

The SRMT regimen as frontline treatment for PCNSL is highly efficacious and well tolerated. (Chinese Clinical Trial Registry number: ChiCTR1900027433).