Prognostic factors in metastatic malignant melanoma treated with combined radiation therapy and hyperthermia

From May 1981 to September 1991, 38 patients with metastatic malignant melanoma were treated with combined radiation therapy and hyperthermia to a total of 97 hyperthermia treatment fields. Prior treatments to these sites included surgery (31 patients, 76 fields), chemotherapy (18 patients, 54 fields), immunotherapy (14 patients, 42 fields) and radiation therapy (7 patients, 13 hyperthermia fields). Hyperthermia was given to fields located in the head and neck region, trunk and extremities in 30, 45 and 22 cases, respectively. Nodular-diffuse tumours were present in 86 fields while 11 fields were treated for microscopic residual tumour deposits. Concurrent radiation therapy was given in 180-400 cGy per fraction, 2-5 times per week for a mean total dose of 4098 cGy per field. Hyperthermia treatments were delivered using either microwave or ultrasound devices (286 and 48 treatments, respectively) with a mean (range) of 3.4 (1-14) hyperthermia treatments per field for a mean (range) of 43 (10-70) min per field. Patients (n = 34; 84 fields) were available for follow-up for a mean (range) of 14.6 (0.4-82.5) months. At 3 weeks post-treatment, 34 fields had complete, ongoing, or partial responses; 39 fields had no response; and there were no recurrences in the 11 fields treated for microscopic residual disease. Local control was maintained in 31% (26/84) fields with a mean follow-up of 14.6 months. At 36 months, five patients remained alive with complete control of their treated local disease. Statistical analyses revealed that patients with soft tissue metastases only, who were older at the time of hyperthermia, had a longer time between initial diagnosis and hyperthermia treatment, received a higher dose of radiation, had no previous chemotherapy, and had small tumour volumes, had a higher initial response. Multivariate analyses revealed that the three-covariate model including time interval between initial diagnosis and hyperthermia treatment, previous chemotherapy, and metastases to soft tissue only, best predicted response. The results of the investigation support the continued study of combined radiation therapy and hyperthermia treatments for selected patients with metastatic melanoma, and indicate that long-term survival can occasionally be obtained with this approach.