Purpose: To determine the toxicity, maximum tolerated dose (MTD), and clinical effectiveness of a 5-week course of accelerated radiotherapy with delayed concomitant boost in locally advanced squamous cell carcinoma of the head and neck (SCCHN).
Methods and materials: Thirty-five patients with untreated T3T4NM0 or TN2 (> 3 cm) N3M0 SCC of the oral cavity, oropharynx, hypopharynx, or larynx were entered in the study between January 1994 and October 1997. The initial target volume was treated with conventional daily fractions. A small field boost covering gross disease was added as a second daily fraction during the last 2 weeks of the 5-week schedule, using a minimum interfraction interval of 6 h. The study was initiated using 180-cGy fractions to deliver a total dose of 63 Gy over 33-35 days. A classical dose escalation strategy was planned to increase the delivered dose in steps using minimum cohorts of three patients, up to a maximum of 70 Gy in 200-cGy fractions.
Results: In the dose escalation study, 4 patients were entered at level 1 (63 Gy), 9 at level 2 (65 Gy), and 8 at level 3 (67 Gy). One patient was withdrawn at level 2 because of unstable angina, and 1 at level 3 because of uncontrolled diabetes. One patient at level 3 failed to complete treatment because of radiation toxicity. RTOG Grade 3 mucositis, dermatitis, or pharyngitis was documented in 1 (25%), 5 (63%), and 7 (100%) evaluable patients at levels 1, 2, and 3, respectively. Grade 4 reactions were documented in 1 patient at each level. One patient at level 3 died 5 weeks post-treatment of unknown causes. Two additional patients at level 3 died of progressive disease and RT toxicity. Sixty-five Gy (level 2) was chosen as the MTD. In the MTD study, 14 additional patients were entered at level 2, providing a total of 22 evaluable patients with a median follow-up of 21 months (range 12-41 months). Grade 3 mucositis, dermatitis, or pharyngitis were documented in 11 (50%), 8 (36%), and 6 (27%) patients, respectively. One patient developed Grade 4 mucositis. A complete response was recorded in 16 (77%). Three of 5 patients with uncontrolled disease and 3 of 3 patients with recurrent disease underwent salvage surgery with no postoperative complications. Radiotherapy controlled disease above the clavicles in 14 (68%). Ultimate locoregional control was achieved in 17 (77%). The disease-free, overall, and cause-specific survival of all patients entered at level 2 was 56%, 76%, and 80%, respectively, at 2 years. Late complications have been limited to 3 patients (trismus, chronic mucosal ulcer, and soft tissue necrosis).
Conclusion: A 5-week course of accelerated radiotherapy with delayed concomitant boost can deliver 65 Gy with acceptable toxicity, encouraging rates of complete response, and locoregional control, and no compromise of salvage surgery in patients with locally advanced SCCHN. The regimen is worthy of further study in a Phase III trial.