Background
Prospective clinical trial (Stanford) evaluating palliative RT combined with ipilimumab in 22 patients with stage IV melanoma. First prospective trial of RT + anti-CTLA-4 immunotherapy in melanoma. RT to 1–2 sites initiated within 5 days of starting ipilimumab. Required ≥1 non-irradiated metastasis ≥1.5 cm for abscopal response assessment.
Interventions and follow up
Arm A: Palliative RT (dose/site at physician discretion) + ipilimumab 3 mg/kg q3wk × 4 cycles; single-arm prospective trial
Arm B: N/A — single-arm desig
Primary endpoint: Safety and efficacy (systemic response rate); secondary: induction of antimelanoma immune response
mFollow up: Median 55 week
Arm B: N/A — single-arm desig
Primary endpoint: Safety and efficacy (systemic response rate); secondary: induction of antimelanoma immune response
mFollow up: Median 55 week
Results
Clinical Benefit Rate: 50% (11/22 patients) — CR + PR + stable disease
Systemic Complete Response: 27.3% (3/22) at median 55-week follow-up
Partial Response: 27.3% — median duration 40 weeks
Immune correlate: Elevated CD8+ activated T-cells associated with response
Systemic Complete Response: 27.3% (3/22) at median 55-week follow-up
Partial Response: 27.3% — median duration 40 weeks
Immune correlate: Elevated CD8+ activated T-cells associated with response
Adverse events
Main adverse events: Combination well-tolerated; no unexpected toxicities beyond known ipilimumab AEs (immune-mediated colitis, hepatitis, hypophysitis). RT-site acute reactions as expected. No unexpected synergistic toxicities observed.
Conclusions
RT combined with ipilimumab is safe and feasible in metastatic melanoma, with 50% clinical benefit rate and 27% complete systemic response — results substantially higher than historical ipilimumab monotherapy data (~10–15% CR/PR). This is the first prospective demonstration of potential abscopal effect enhancement by combining RT with immunotherapy.
Key Limitations
Key Limitations: Small sample (n=22); no control arm; heterogeneous RT doses/sites; response assessment timing variable; selection bias (PS 0–1 required); ipilimumab now largely replaced by anti-PD1 therapy (pembrolizumab, nivolumab) with higher response rates; no established RT dose/fractionation schedule for optimal immunomodulation.
Clinical Context
This trial generated significant interest in RT + immunotherapy combinations ("radioimmunotherapy") and the abscopal effect. Anti-PD1 agents (pembrolizumab, nivolumab) are now the standard for metastatic melanoma; RT + anti-PD1 combinations are under investigation. The immunostimulatory dose and timing of RT for optimal immune enhancement remains an active research area (SBRT vs hypofractionated vs conventional RT).