Radiotherapy and hyperthermia. Analysis of clinical results and identification of prognostic variables.

Site- and tumor-specific data obtained from two groups of patients with head and neck and melanoma lesions, respectively, showed that both immediate response and response duration were enhanced by the addition of heat. Two important variables, however, such as tumor volume and "isoeffect thermal dose" appeared to influence local tumor control. The volume effect was less pronounced in the lesions treated with radiotherapy plus heat than in those treated with radiotherapy alone, suggesting that the addition of heat was more damaging to the large than to the small lesions. Furthermore, a striking isoeffect thermal dose-response relationship was shown in head and neck lesions. Those data were collected and used to design a mathematical model relating the probability of local control to clinical and treatment variables. The analysis shows that, by using the same radiation parameters, the probability of local tumor control is a function of both "isoeffect thermal dose" and tumor volume.