Randomized trial of one versus two adjuvant hyperthermia treatments per week in patients with superficial tumours

One test for thermotolerance development in a clinical situation is to evaluate the effects of altering the hyperthermia fractionation interval on tumour response to thermoradiotherapy. Between 1983 and 1990 44 evaluable advanced superficial tumours of miscellaneous origin in 41 patients were randomized to receive either once-weekly or twice-weekly external microwave hyperthermia treatments combined with radiation therapy. The mean age of patients was 62 years, and 85% had failed previous therapy. All lesions were less than 8 x 8 x 4 cm (L x W x D) and were heated by external 915 MHz microwaves. The mean radiation dose was 44 +/- 3 Gy (mean +/- SE) in the once-weekly group and 46 +/- 3 Gy in the twice-weekly group (p = 0.64). The mean volume of the lesions heated once weekly was 17 +/- 6 versus 23 +/- 5 cm3 for those heated twice weekly (p = 0.45). Hyperthermia was administered once weekly for 4.6 +/- 0.2 sessions (range 3-7) or twice weekly for 8.1 +/- 0.3 sessions (range 4-10). Thermometry was performed using 3.4 +/- 0.2 catheters and 5.1 +/- 0.6 thermal sensors per tumour in the once-weekly group, and 2.7 +/- 0.2 catheters and 5.8 +/- 0.3 thermal sensors per tumour in the twice-weekly group. Of the 44 evaluable randomized lesions a complete response (CR) at 2 months post-treatment was observed in 59% (13/22) heated once weekly and 55% (12/22) in those heated twice weekly. The prognostic factors predictive of tumour complete response were found by logistic regression analysis to be radiation dose and tumour volume, while the prognostic factors predictive of duration of response (Cox proportional hazards analysis) were median minimum tumour temperature (Tmin), minimum tumour temperature during the first heat treatment (Tmin1) and tumour volume. The duration of local control in lesions with Tmin < or = 39.5 degrees C was 11.7 +/- 1.9 months while for lesions with Tmin > 39.5 degrees C it was 23.0 +/- 4.2 months (p = 0.01). The ED50 was calculated by logistic regression to be 40 Gy (95% CI = 22-54 Gy) for once- and twice-weekly heated lesions. There was not a significant difference in tumour response or duration of response between populations randomized to receive once- versus twice-weekly hyperthermia treatments. There was also no difference in skin reaction rates between once- and twice-weekly hyperthermia treatments, nor could a correlation be found between any thermal parameter and skin reactions.(ABSTRACT TRUNCATED AT 400 WORDS)