Effects on Survival and Neurocognitive Functions of Whole-Brain Radiotherapy (WBRT) and Autologous Stem Cell Transplantation (ASCT) as Consolidation Options after High-Dose Methotrexate-Based Chemoimmunotherapy in Patients with Newly Diagnosed Primary CNS Lymphoma (PCNSL): Results of the Second Randomization of the IELSG32 Trial

Introduction: IELSG32 is an international randomized phase II trial with 2 key clinical questions in pts with PCNSL. The first question focused on optimal induction therapy, and results of the 1st randomization have demonstrated that MATRix combination (methotrexate (MTX), cytarabine (ARAC), thiotepa, rituximab (R)) is associated with significantly better outcome [Ferreri AJ, et al. Lancet Haematol 2016]. The second question addresses the efficacy and neurotolerability of ASCT, as an alternative to WBRT as consolidation. Herein, we report the results of the 2nd randomization (NCT01011920).

Methods: HIV-neg pts 18-70 ys and ECOG PS ≤3 with new histology-proven PCNSL and measurable disease were randomly assigned to receive 4 courses of MTX-ARAC (arm A); or R-MTX-ARAC (arm B); or MATRix (arm C). ASC were collected after 2^nd c. Pts with responsive or stable disease were further randomized between WBRT 36 ± 9 Gy (arm D) and BCNU-thiotepa conditioned/ASCT (arm E). Stratification parameters were induction arm and response . Primary endpoint of the 2^ndrandomization was 2-year PFS. To demonstrate a 2-yr PFS improvement from 65% (P0) to 85% (P1), 52 pts/arm (one-sided; α 5%; β 95%) were required. Consolidation arm would be considered effective if ≥40 pts were progression-free survivors at 2 ys. Analyses were performed on an intention-to-treat (ITT) basis. Effects of consolidation treatments on neurocognitive functions and quality of life (QoL) were assessed with the IPCG tests panel and EORTC-QLQ at baseline, after treatment and every 6 months afterwards.

Results: 227 pts were enrolled in 52 centers of 5 countries; 219 assessable pts were referred to 1st randomization (arm A 75; B 69; C 75). 167 pts had responsive or stable disease after induction: 49 pts were excluded from 2nd randomization (poor mobilization, poor condition or patients' refusal); 118 pts were thus randomized (59 pts/arm) and constitute the study population (median age 58 ys; range 18-70). 15 (13%) pts had high IELSG risk, 3 pts had ocular disease and 20 pts had meningeal disease; with the exception of a higher male prevalence in arm D, there were no differences in clinical presentation between two arms; There were 6 protocol violations: 4 pts randomly allocated to arm D were treated with ASCT and 2 pts randomly allocated to arm E were treated with WBRT; 5 pts (D 2; E 3) refused consolidation. Therefore, per-protocol (PP) groups consisted of 55 pts treated with WBRT and 58 with ASCT.

Both consolidation therapies were well tolerated. Grade 4 toxicity was uncommon (≤5% of pts); as expected, hematological toxicity was more common in arm E (neutropenia 5% vs. 71%; p=0.00001 - thrombocytopenia 2% vs. 72%; p=0.00001). There were 2 toxic deaths (infections), both in arm E. Neuropsychological tests showed a significant impairment of attention/executive functions and a non-significant trend to impaired memory among pts treated with WBRT, whereas pts treated with ASCT exhibited improved functions. Both consolidation therapies were associated with significant improvement in language and QoL.

Both WBRT and ASCT were active and resulted in significant improvement in CR rate: from 54% after induction to 95% (95%CI: 90-100) after consolidation in arm D, and from 53% to 93% (95%CI: 87-99) in arm E. After a median follow-up of 40 months (range 24-76), there were 20 events (16 relapses, 2 PDs, 2 off-therapy deaths) in arm D, and 25 events (18 relapses, 2 PDs, 2 toxic deaths, 3 off-therapy deaths) in arm E. Importantly, WBRT and ASCT were both effective, with a number of progression-free survivors at 2 ys equal to the pre-determined efficacy threshold: 40 among both the first 52 arm-D and 52 arm-E pts.

There were no significant differences in PFS between WBRT and ASCT; on ITT basis, the 2-yr PFS was 80 ± 5% after WBRT and 70 ± 6% after ASCT; per protocol, the 2-yr PFS was 76 ± 6% and 75 ± 6%, respectively. In multivariate analysis, IELSG risk group, number of lesions and induction arm were independently associated with PFS; gender, CSF cytology status and consolidation arm were not. Forty-two pts randomized to arm D and 37 randomized to arm E are alive, with 2-year OS of 85 ± 5% and 71 ± 6% (p=0.12), respectively.

Conclusions: WBRT and ASCT are both feasible, active and effective as consolidation therapies after high-dose-MTX-based chemoimmunotherapy in pts ≤70 ys with PCNSL. Potential impairment of specific neurocognitive functions after WBRT should be considered at the time of therapeutic decision.