High-Dose Chemotherapy and Autologous Stem Cell Transplant in Elderly and Fit Primary CNS Lymphoma Patients - a Multicenter Study By the Cooperative PCNSL Study Group (MARTA study) (2022)

Introduction: High-dose methotrexate (HD-MTX) based induction chemo-immunotherapy followed by high-dose chemotherapy and autologous stem cell transplantation (HCT-ASCT) has been shown to be feasible and effective in younger and in selected elderly PCNSL patients. We aimed to investigate this treatment approach in patients > 65 years with newly diagnosed PCNSL in a multicentre study. Methods: This open-label, multicentre, single arm phase II study was conducted at 15 German centres (DRKS 00011932). Main eligibility criteria included newly diagnosed PCNSL, immunocompetence, age > 65 years, Eastern Cooperative Oncology Group Performance Status (ECOG PS) ≤ 2, and adequate organ function. Induction treatment consisted of two 21-day cycles of HD-MTX 3.5 g/m² (day 1), cytarabine 2 g/m² twice daily (days 2, 3) and rituximab 375 mg/m² before and after each chemotherapy with stem cell harvest after the 1st cycle. Patients not suffering disease progression subsequently received consolidation treatment with HCT-ASCT with rituximab 375 mg/m² (day -8), busulfan 3.2 mg/kg (days -7, -6), thiotepa 5 mg/kg/d (days -5, -4) and reinfusion of stem cells (day 0). Primary endpoint was progression-free survival (PFS) at 1 year by intention-to-treat (ITT). Secondary endpoints included overall survival (OS), treatment response and toxicities. Results: Between Nov 2017 and Sept 2020, we registered 57 patients. Five patients were excluded because of systemic lymphoma manifestation, absence of measurable radiologic lesion(s), inadequate renal function, ECOG PS >2 and deterioration before the start of study treatment. Finally, 52 eligible patients were included in the ITT population. Mean age was 72 years (range 65-80 years), 27/52 (51.9%) patients initially presented with an ECOG PS > 1. All patients started induction chemo-immunotherapy, 45 of 52 (86.5%) patients completed induction treatment. Thirty-seven of 52 (71.2%) patients proceeded to HCT-ASCT. Most common serious adverse events were infections, renal failure and (cerebro)vascular events, which mainly occurred during induction treatment. Overall, 22 (42.3%) patients died, 12 of whom (23.1%) without evidence of disease progression or relapse. Three (5.8%) patients died because of treatment-related complications, all of them during induction treatment. An additional patient died within 30 days after HCT-ASCT due to fatal viral pneumonia, main other non treatment-related causes of deaths were late infections and (cerebro)vascular events. Forty-one of 52 (78.8%) patients responded to induction treatment; 23 (44.2%) patients achieved a (unconfirmed) complete response and 11 (21.2%) patients a partial response 30 days after HCT-ASCT. After an estimated median follow-up of 23 months, PFS at 12 and 24 months was 57.7% (95% CI 43.2-69.7%) and 54.8% (40-67.4%), respectively; median PFS was 41.1 months (95% CI 6.7 to not calculable). Overall survival at 12 and 24 months was 63.1% (95% CI 48.4-74.7%) and 60.5% (95% CI 45.5-72.5%), respectively; median OS was 41.1 months (95% CI 10.3 to not calculable). Of those 37 patients undergoing HCT-ASCT, 2-year PFS and OS rates were 71.7% (95% CI 53.4-83.8%) and 80.8% (95% CI 63.8-90.3%), respectively. Conclusions: Feasibility and efficacy of HCT-ASCT in selected elderly patients with newly diagnosed PCNSL are confirmed in a multicenter setting with survival rates comparable to those of younger cohorts. Nevertheless, non-relapse mortality remains a major challenge in this vulnerable patient population emphasizing that standardized assessment of eligibility for intensive treatment is of utmost importance. This will be addressed in the upcoming randomized phase III PRIMA-CNS trial (DRKS00022768). Final data analysis is currently ongoing and will be presented in detail at the meeting.