Randomized clinical trials have demonstrated hyperthermia (HT) enhances radiation response. These trials, however, generally lacked rigorous thermal dose prescription and administration. We report the final results of a prospective randomized trial of superficial tumors (! 3 cm depth) comparing radiotherapy versus HT combined with radiotherapy, using the parameter describing the number of cumulative equivalent minutes at 43°C exceeded by 90% of monitored points within the tumor (CEM 43°C T90) as a measure of thermal dose.
This trial was designed to test whether a thermal dose of more than 10 CEM 43°C T90 results in improved complete response and duration of local control compared with a thermal dose of ! 1 CEM 43°C T90. Patients received a test dose of HT ! 1 CEM 43°C T90 and tumors deemed heatable were randomly assigned to additional HT versus no additional HT. HT was given using microwave spiral strip applicators operating at 433 MHz.
One hundred twenty-two patients were enrolled; 109 (89%) were deemed heatable and were randomly assigned. The complete response rate was 66.1% in the HT arm and 42.3% in the no-HT arm. The odds ratio for complete response was 2.7 (95% CI, 1.2 to 5.8; P ! .02). Previously irradiated patients had the greatest incremental gain in complete response:23.5% in the no-HT arm versus 68.2% in the HT arm. No overall survival benefit was seen.
Adjuvant hyperthermia with a thermal dose more than 10 CEM 43°C T90 confers a significant local control benefit in patients with superficial tumors receiving radiation therapy.