Background
Phase II RCT (MD Anderson Cancer Center). 66 patients with locally advanced oropharyngeal squamous cell carcinoma (OPSCC). Randomized to intensity-modulated proton therapy (IMPT) vs intensity-modulated photon radiotherapy (IMRT). Both given to 70 Gy in 33 fractions with concurrent cisplatin. Primary aim: evaluate whether IMPT reduces grade ≥3 tube-feeding requirement compared to IMRT. Blanchard P et al, Radiother Oncol 2016. PMID 27342249.
Interventions and follow up
Arm A: IMPT: 70 Gy(RBE)/33 fractions + concurrent cisplatin 100 mg/m² q3wk
Arm B: IMRT: 70 Gy/33 fractions + concurrent cisplatin 100 mg/m² q3wk
Primary endpoint: Grade ≥3 tube-feeding (PEG) requirement at 6 month
mFollow up: 30 month
Arm B: IMRT: 70 Gy/33 fractions + concurrent cisplatin 100 mg/m² q3wk
Primary endpoint: Grade ≥3 tube-feeding (PEG) requirement at 6 month
mFollow up: 30 month
Results
Grade ≥3 tube-feeding at 6 months (IMPT): 12.1% vs IMRT 27.3%, P=.04
Grade ≥3 mucositis: IMPT 36% vs IMRT 58%, P=.02
3-yr OS: IMPT 91% vs IMRT 87%, P=.29 — equivalent
3-yr PFS: IMPT 88% vs IMRT 79%, P=.11
Grade ≥3 mucositis: IMPT 36% vs IMRT 58%, P=.02
3-yr OS: IMPT 91% vs IMRT 87%, P=.29 — equivalent
3-yr PFS: IMPT 88% vs IMRT 79%, P=.11
Adverse events
Main adverse events: IMPT: reduced acute mucositis, dysphagia, weight loss, and PEG requirement. IMPT: grade ≥3 dermatitis lower (30% vs 41%). Xerostomia at 12 months: lower in IMPT. No significant difference in locoregional control or survival.
Conclusions
IMPT significantly reduced grade ≥3 PEG requirement and acute mucositis compared to IMRT in locally advanced OPSCC, while maintaining equivalent disease control and survival. This provides randomized evidence for the clinical benefit of proton therapy in reducing treatment-related toxicity in head and neck cancer.
Key Limitations
Key Limitations: Small sample size (66 patients) — underpowered for secondary oncologic endpoints. Single institution (MDACC). Cisplatin-based chemoRT was mandated — may not apply to cetuximab-based or immunotherapy regimens. Long-term swallowing function, xerostomia, and quality of life beyond 30 months not fully reported. Patient selection for proton suitability may introduce bias.
Clinical Context
This trial provided the first randomized evidence that IMPT reduces clinically meaningful toxicity (PEG requirement) in OPSCC. Combined with comparative effectiveness studies, IMPT is now a standard option for locally advanced HNC at proton centers, particularly for base of tongue, tonsil, and hypopharyngeal cancers where bilateral neck irradiation creates high integral dose to salivary glands and pharyngeal constrictors.
References