Background
Phase II trial (RTOG 9310). 98 patients with primary CNS lymphoma (PCNSL). All received high-dose methotrexate (MTX) 2.5 g/m² × 5 cycles followed by whole-brain radiotherapy (WBRT) 45 Gy. A subsequent analysis (Fisher J Neurooncol 2005) examined delayed neurotoxicity by age in this cohort. Prior to RTOG 9310, WBRT alone was standard; this trial established MTX-based induction followed by WBRT.
Interventions and follow up
Arm A: MTX 2.5 g/m² IV × 5 cycles → WBRT 45 Gy (1.8 Gy/fx) + boost to 54 Gy → cytarabine × 2 cycles (n=98)
Arm B: N/A (single-arm phase II)
Primary endpoint: Overall survival and response rate
mFollow up: Not specified
Arm B: N/A (single-arm phase II)
Primary endpoint: Overall survival and response rate
mFollow up: Not specified
Results
Median OS: 36.9 months
2-yr OS: 63%
CR rate: 58%
Delayed neurotoxicity: Significantly higher in patients >60 years after WBRT (dementia in ~30–40% at 2 years)
2-yr OS: 63%
CR rate: 58%
Delayed neurotoxicity: Significantly higher in patients >60 years after WBRT (dementia in ~30–40% at 2 years)
Adverse events
Main adverse events: Grade ≥3 hematologic toxicity with MTX common. Delayed neurotoxicity (dementia, ataxia, urinary incontinence) was the major late effect, significantly more common in older patients (>60 years) receiving WBRT.
Conclusions
MTX-based induction followed by WBRT achieves significantly better OS compared with WBRT alone for PCNSL. However, delayed neurotoxicity is severe in patients >60 years and prompted exploration of reduced-dose WBRT and WBRT-deferral strategies in subsequent trials.
Key Limitations
Key Limitations: Single-arm phase II — no randomized comparison. Age-related neurotoxicity was not a pre-planned endpoint (post-hoc analysis). MTX dose (2.5 g/m²) is lower than currently recommended (3.5–8 g/m²). The combination with WBRT has largely been abandoned in consolidation for elderly patients due to unacceptable neurotoxicity.
Clinical Context
RTOG 9310 was a landmark trial establishing combined modality (MTX + WBRT) as superior to WBRT alone, but the severe neurotoxicity prompted the MSKCC approach of MTX-based induction + deferred or reduced-dose WBRT. Current IELSG-32 and PRECIS trials guide modern PCNSL treatment. For patients <60, WBRT 23–36 Gy consolidation after MTX remains an option; elderly patients receive autologous SCT or HD-cytarabine consolidation to avoid WBRT.
References