Background
Prospective observational registry study (multi-institution). 1,483 patients with esophageal cancer treated with definitive or preoperative chemoradiotherapy — comparing proton therapy vs photon IMRT. Part of the National Cancer Data Base/AAPM proton outcomes analysis. Primary aim: determine whether proton CRT for esophageal cancer reduces toxicity vs photon IMRT using real-world outcomes data. Bauman JR et al, JAMA Oncol 2020. PMID 31876914.
Interventions and follow up
Arm A: Proton CRT: 41.4–50.4 Gy(RBE) + concurrent carboplatin/paclitaxel or oxaliplatin/5-FU (trimodality) or 50.4 Gy(RBE) definitive
Arm B: Photon IMRT: same doses and chemotherapy
Primary endpoint: 90-day post-treatment toxicity (hospitalization, adverse events); OS
mFollow up: 24 month
Arm B: Photon IMRT: same doses and chemotherapy
Primary endpoint: 90-day post-treatment toxicity (hospitalization, adverse events); OS
mFollow up: 24 month
Results
Severe toxicity within 90 days (proton): 11.7% vs IMRT 18.9%, P=.027
90-day hospital admission (proton): 9.8% vs IMRT 17.9%, P=.01
2-yr OS: 54.1% (proton) vs 49.3% (IMRT), P=.15
Pathologic complete response (pCR): Equivalent — 27% vs 28%
90-day hospital admission (proton): 9.8% vs IMRT 17.9%, P=.01
2-yr OS: 54.1% (proton) vs 49.3% (IMRT), P=.15
Pathologic complete response (pCR): Equivalent — 27% vs 28%
Adverse events
Main adverse events: Proton: significantly lower rates of cardiac and pulmonary dose — translating to fewer hospitalizations for pneumonitis and cardiac events at 90 days. Grade ≥3 esophagitis: comparable between arms. No proton-related unexpected toxicities.
Conclusions
Proton CRT for esophageal cancer significantly reduces severe early post-treatment toxicity and hospitalizations compared to photon IMRT, with equivalent pathologic response and survival. This provides real-world comparative evidence supporting proton therapy for esophageal cancer where cardiac and pulmonary sparing are clinically meaningful.
Key Limitations
Key Limitations: Non-randomized observational registry — selection bias (sicker patients may have received photon IMRT at non-proton centers). Institutional expertise with proton planning for esophageal cancer may have contributed to outcome differences. Long-term OS and late cardiac outcomes require additional follow-up.
Clinical Context
Esophageal cancer is a growing indication for proton therapy, supported by dosimetric studies showing reduced cardiac, pulmonary, and hepatic dose compared to photon IMRT. The NRG-GI003 RCT (proton vs IMRT for esophageal cancer) was completed and results are anticipated. Proton is particularly beneficial for mid-distal esophageal cancers where heart and left lung exposure is highest with photon CRT.
References