Purpose: To determine whether any difference in toxicity or efficacy occurs when head and neck cancer patients are treated postoperatively with (60)C0, 4 MV, or 6 MV photon beam.
Methods and materials: This is a secondary analysis of the Intergroup Study 0034. Three hundred ninety-two patients were evaluable for comparison between treatment with (60)C0, 4 MV, or 6 MV photon beam. All patients had advanced but operable squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, or larynx. Patients were randomized following surgical resection to receive treatment with either postoperative irradiation alone, or postoperative irradiation plus three cycles of cisplatin and 5-fluorouracil. Patients were categorized as having either "low risk" or "high risk" treatment volumes based on whether the surgical margin was 5 mm or less, presence of extra capsular nodal extension, and/or carcinoma in situ at the surgical margins. Low-risk volumes received 50-54 Gy, and high-risk volumes were given 60 Gy. Patients were compared in regards to acute and late radiotherapy toxicities as well as overall survival and loco-regional control according to the beam energy used.
Results: One-hundred fifty-seven, 140, and 95 patients were treated by (60)C0, 4 MV, and 6 MV, respectively. No differences were seen in acute or late toxicity among treatment groups. Locoregional control was achieved in 75%, 79%, and 80% of patients treated with (60)C0, 4 MV, or 6 MV (p = 0.61). Patients treated with 6 MV had a higher incidence of ipsilateral neck failure as first event (13%) than patients treated by (60)C0 and 4 MV (9%). This difference was not statistically significant.
Conclusion: No differences in outcome, acute, or late toxicity were discernible in patients with advanced head and neck cancer treated with (60)C0, 4 MV, or 6 MV. This result should be interpreted with caution as increased incidence, albeit nonsignificant, of ipsilateral neck recurrence was observed in patients treated with 6 MV and the power of the study to detect a statistically significant difference is small.