The influence of beam energy on the outcome of postoperative radiotherapy in head and neck cancer patients: Secondary analysis of RTOG 85-03

Purpose: To determine whether any difference in toxicity or efficacy occurs when head and neck cancer patientsare 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 betw een treatment with (60)C0, 4 MV, or. 6 MV photon beam. All patients had adv anced but operable squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, or larynx. Patients were randomized following surgical resecti on to receive treatment with either postoperative irradiation alone, or pos toperative irradiation plus three cycles of cisplatin and 5-fluorouracil. P atients were categorized as having either "low risk" or "high risk" treatme nt 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 gi ven 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, or 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). Pat ients 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 di fference was not statistically significant. Conclusion: No differences in outcome, acute, or late toxicity were discern ible 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 in cidence, albeit nonsignificant, of ipsilateral neck recurrence was observed in patients treated with 6 MV and the power of the study to detect a stati stically significant difference is small. (C) 2000 Elsevier Science Inc.