Background: The treatment of advanced, inoperable, or recurrent parotid tumors represents a clinical challenge. The results obtained with conventional radiotherapy are disappointing. To improve the early response and local control of parotid tumors, local microwave hyperthermia was used in combination with ionizing radiation in a biinstitutional Phase I/II study.
Methods: From 1984 to 1991, 13 patients (20 lesions) with advanced (10 lesions) or recurrent (10 lesions) parotid tumors (15 primaries and the remaining 5 nodal metastases), were treated with 300-915 MHz of external hyperthermia after external irradiation. Heat was applied twice weekly at a minimum desired temperature of 42.0 degrees C for 30 minutes at steady state. Ionizing radiation was delivered using photon, electron, or mixed electron-photon beams; the prescribed total dose was 70 Gy and 30 Gy for untreated and previously treated lesions, respectively; the median computed total dose was 66 Gy for previously untreated patients (range, 56-70 Gy) and 30 Gy for previously irradiated patients (range, 28-32 Gy).
Results: Acute side effects were limited. Major acute toxicities included three patients (15%) with superficial necrosis, two of three who healed spontaneously in 4 and 6 months. Clinical response evaluated during the third month after the completion of therapy found that 16/20 patients (80%) had a complete response (CR), and 4 (20%) had a partial response. Four out of 16 patients who had CRs (20%) had a local recurrence, resulting in an actuarial local control at 5 years of 62.3 +/- 13.2%.
Conclusions: The combined treatment of local microwave hyperthermia and ionizing radiation proved to be feasible and moderately toxic for patients with advanced, inoperable, or recurrent parotid tumors. Even if clinical result evaluation was not the study endpoint, early response, and 5-year local control rates were encouraging.