Purpose: In 1984 we began treating patients with squamous cell carcinomas of the larynx and hypopharynx with hyperfractionated radiotherapy. Patients received 76.8 Gy in 1.2 Gy fractions twice daily, with a 4 h interfraction interval. In 1988, this schedule was modified in patients treated with shrinking field techniques. The dose per fraction was slightly reduced (while not changing the total dose), and the interfraction interval was increased to 6 h. The goal was to decrease toxicity while maintaining satisfactory local-regional control. This retrospective study analyzes the results of this schedule modification.
Methods and materials: Two hundred thirty-six patients were included in the analysis. Distribution of patients by primary site and T stage was as follows: supraglottic larynx, 120 patients; hypopharynx, 70; true vocal cord, 24; and oropharynx, 22; T1, 5 patients; T2, 118; T3, 93; T4, 19; and Tx, 1. Ninety-nine patients presented with cervical nodal disease. Seventy-eight patients (group A), including 16 treated with induction chemotherapy, were treated throughout with 1.2 Gy fractions twice daily and a 4-h interfraction interval. Subsequently, 158 patients (group B), 57 of whom received chemotherapy, received 1.1 Gy fractions to 55 Gy, and then 1.2 Gy fractions to their boost volumes to 76.6 Gy. The interfraction interval was 6 h. Median follow-up was 91 and 35 months for group A and B, respectively.
Results: Two-year actuarial survival, local control, and ultimate local rates were 70%, 75%, and 85%, respectively. Differences between survival rates for group A and group B were not statistically significant, with 2-year rates of 66% and 72%, respectively. Overall local control rates at 2 years were 77% and 74%, respectively, for groups A and B (p = 0.22). However, there was a trend toward inferior results in group B patients with T3 disease (67% at 2 years compared to 76% in group A, p = 0.13). Confluent mucositis and persistent mucositis developed in 52% and 14% of group A patients, but only 37% and 4% of group B patients (p = 0.02 and p < 0.01, respectively). There was a near significant trend toward fewer late complications in group B who developed an 8% complication rate at 3 years compared to 15% of group A patients (p = 0.07).
Conclusions: The net effect of reducing the dose per fraction to 1.1 Gy twice daily for fields covering gross disease and subclinical sites, and increasing the interfraction interval to 6 h was to reduce the incidence of both acute and late complications. Excellent overall local control rates (85%) for T2 lesions were achieved with both hyperfractionation regimens and we, therefore, continue to treat patients with T2 tumors with the modified schedule. The overall results in selected patients with T3 lesions was also satisfactory (69%), but as there was a trend towards poorer local control in patients treated with 1.1 Gy fractions, we recommend using 1.2 Gy for the entire treatment of these patients, while maintaining the 6 h interfraction interval to reduce the risk of late complications.