From November 1990 to September 1991, 23 adults with high-risk, nonmetastatic sarcomas (20 soft-tissue sarcomas and 3 chondrosarcomas) were entered in a pilot protocol (RHT-91) involving regional hyperthermia combined with systemic chemotherapy followed by surgery. Of these patients, 12 had undergone previous surgery and/or radiation, 5 had received previous multidrug chemotherapy, and 6 were previously untreated. A tumor size of > 8 cm and/or an extracompartmental tumor location (11 patients) or local recurrence (12 patients) were defined as high-risk factors in addition to tumor grading (21 patients had grade 2 or 3 sarcomas). Regional hyperthermia was produced by an electromagnetic deep-regional-heating device. For systemic chemotherapy, all patients received etoposide/ifosfamide/doxorubicin (EIA) and mesna, with regional hyperthermia being given only on days 1 and 4 in repeated EIA/regional hyperthermia cycles every 3 weeks. Tumor temperatures (range, 40 degrees-44 degrees C) were measured by invasive thermometry in all patients during each regional hyperthermia treatment. A total of 181 regional hyperthermia treatments were applied within the pelvic region (11 patients) or extremities (12 patients) bearing relatively large tumors (mean volume, 848 cm3). By the cutoff date for this analysis (October 15, 1991), 13 patients had undergone surgery after receiving 2-6 (mean, 3.8) cycles of EIA chemotherapy combined with regional hyperthermia; all tumors except one were resected without disfiguration. In 22 evaluable patients (minimum, 2 EIA plus regional hyperthermia cycles), the clinical response rate was 27%, with 6 patients showing partial responses (PRs). In addition, a pathologic response to preoperative thermochemotherapy was evaluable in 13 patients, with 4 responders (31%) having > 50% histologic necrosis. In all, 3 of the responders (1 PR and 2 patients with > 50% histologic necrosis) relapsed within 3 months of surgical resection. The other 7 responding patients (5 PRs and 2 patients with > 50% histologic necrosis) showed stable disease with local tumor control. The study (RHT-91) is continuing as a multicenter phase II trial (opened on November 19, 1991) in patients with high-risk soft-tissue sarcomas to test the potential of preoperative thermochemotherapy in regard to local control and survival.