Background
Phase III RCT (RTOG 8501). 129 patients with esophageal cancer (84% squamous cell carcinoma, 16% adenocarcinoma) allocated to radiation therapy alone (64 Gy) vs combined chemoradiotherapy (cisplatin 75 mg/m² day 1 + 5-FU 1000 mg/m²/day continuous for 96 hours, cycles 1–4 concurrent with 50 Gy, then 2 additional cycles). This is the landmark trial establishing CRT as standard over RT alone for esophageal cancer. Updated survival results reported by Cooper et al in 1999 after median follow-up of 8 years.
Interventions and follow up
Arm A: Concurrent CRT: cisplatin/5-FU (4 cycles) + 50 Gy in 25 fractio
Arm B: Radiation therapy alone: 64 Gy
Primary endpoint: Overall survival
mFollow up: Median 8 years (Cooper 1999 update)
Arm B: Radiation therapy alone: 64 Gy
Primary endpoint: Overall survival
mFollow up: Median 8 years (Cooper 1999 update)
Results
5-year OS: 26% (CRT) vs 0% (RT alone)
8-year OS: 22% (CRT) vs 0% (RT alone) — no long-term survivors in RT alone arm
Median OS: 14.1 mo (CRT) vs 9.3 mo (RT alone), P<.001
Local/regional failure: Lower in CRT arm
Distant metastases: 22% (CRT) vs 19% (RT alone) — similar
8-year OS: 22% (CRT) vs 0% (RT alone) — no long-term survivors in RT alone arm
Median OS: 14.1 mo (CRT) vs 9.3 mo (RT alone), P<.001
Local/regional failure: Lower in CRT arm
Distant metastases: 22% (CRT) vs 19% (RT alone) — similar
Adverse events
Main adverse events: CRT arm: significantly higher acute toxicity — grade 3–4 hematologic toxicity, esophagitis, nausea/vomiting compared to RT alone. Treatment-related deaths: higher in CRT arm (2 deaths vs 0 in initial report). Late toxicity: esophageal stricture in some patients.
Conclusions
Combined chemoradiotherapy (cisplatin/5-FU + 50 Gy) significantly prolongs survival in esophageal cancer compared to radiation alone (64 Gy), with 26% 5-year survivors vs no long-term survivors in the RT-alone arm. The RT arm was therefore closed early at interim analysis. RTOG 8501 established concurrent CRT as the standard definitive treatment for non-surgically managed esophageal cancer.
Key Limitations
Key Limitations: The RT-alone arm received a higher dose (64 Gy) which is now known to not improve outcomes vs standard-dose CRT (per INT 0123 which showed 64.8 Gy was not better than 50.4 Gy); had the RT arm used 50.4 Gy, the survival difference might differ. Predominantly SCC histology (84%). The trial was designed and accrued in the 1980s with older RT techniques (2D planning). Concurrent chemotherapy has evolved significantly since then. A subsequent trial (INT 0123) refined the optimal radiation dose.
Clinical Context
RTOG 8501 fundamentally changed the management of esophageal cancer. The standard definitive CRT regimen of cisplatin/5-FU + 50.4 Gy (as refined by INT 0123) remains the backbone of non-surgical treatment. Carboplatin/paclitaxel and FOLFOX are increasingly used as concurrent chemotherapy alternatives (PRODIGE 5). For patients with locally advanced esophageal cancer not suitable for surgery, definitive CRT at 50.4 Gy is standard.