CALGB 50202

Background

CALGB 50202 was a phase II single-arm trial evaluating a novel induction and consolidation regimen for newly diagnosed primary CNS lymphoma (PCNSL) in immunocompetent patients (n=44; median age 57, range 26–80; DLBCL histology in virtually all). Prior to this trial, high-dose methotrexate (HD-MTX) monotherapy and MTX-based combination regimens had become standard for PCNSL, but optimal combination partners and consolidation strategies were undefined. CALGB 50202 tested MTX, temozolomide, and rituximab (MT-R) as induction followed by etoposide + cytarabine (EA) consolidation to replace whole-brain radiotherapy (WBRT), aiming for durable remission with preserved neurocognitive function.

Interventions and follow up

Induction (MT-R): MTX 8 g/m² + temozolomide 150 mg/m² + rituximab 375 mg/m²
Consolidation (EA): high-dose etoposide 5 mg/kg q12h × 4d + cytarabine 2 g/m² q12h × 4d; no whole-brain radiotherapy
Primary endpoint: 2-year PFS
Secondary: OS, CR rate, safety, neurocognitive function
mFollow-up: 4.9 years

Results

CR/CRu after induction: 66%
2-yr PFS: 57% (95% CI 43–72%); among patients completing EA consolidation (n=31) 79%
2-yr OS: 65% (95% CI 51–79%)
mPFS: 2.4 years
CSF response (leptomeningeal involvement): 75%; neurocognitive testing showed no significant deterioration vs baseline at follow-up

Adverse events

During induction (Grade ≥3): mucositis 16%, transaminase elevation 14%, fatigue 14%, neutropenia 34%; MTX renal toxicity (Grade ≥3 creatinine) 5% (managed with leucovorin rescue)
During EA consolidation (Grade ≥3): neutropenia 81%, thrombocytopenia 74%, febrile neutropenia 32%; 1 treatment-related death (sepsis during consolidation)
Infusion-related: rituximab reactions Grade 1–2 in 18%

Conclusions

MT-R induction followed by EA consolidation achieved a 2-year PFS of 57% and preserved neurocognitive function without whole-brain radiotherapy in newly diagnosed PCNSL, demonstrating that a WBRT-sparing approach using HD-MTX-based combination induction and non-WBRT consolidation can produce durable remissions and avoid the delayed neurotoxicity of cranial radiation in this disease.

Key Limitations

Single-arm Phase II — no randomized comparator; small sample (n=44) limits statistical precision; observed outcomes may not be replicated in larger Phase III trials; EA consolidation involved significant hematologic toxicity and treatment-related mortality risk; not all patients completed consolidation (7/44 did not receive EA); temozolomide penetration into CNS lymphoma uncertain — may add toxicity without proportionate benefit; no stratification by MSKCC prognostic score or IPI; no ASCT comparison; neurocognitive endpoints not fully powered; rituximab CNS penetration limited by blood-brain barrier; outcomes may reflect favorable patient selection at academic centers.

Clinical Context

CALGB 50202 contributed to the evidence base for WBRT-sparing induction strategies in PCNSL, establishing MT-R as a building block for subsequent regimens. The IELSG-32 trial (MATRix induction) subsequently demonstrated superior CR rates with the addition of thiotepa + rituximab to MTX + cytarabine. Current best-practice induction for fit PCNSL patients is MATRix (MTX + cytarabine + thiotepa + rituximab), followed by ASCT consolidation (IELSG-32 Part 2, PRECIS) in eligible patients per ESMO/EANO guidance. WBRT consolidation, though effective, is reserved for patients not eligible for ASCT due to neurocognitive toxicity concerns with aging. MT-R (without thiotepa) remains an option for patients unsuitable for full MATRix intensity, particularly elderly or frail patients.

References