Ultrasonic hyperthermia and drugs as therapy for human tumor xenografts

Ultrasonic energy can generate controlled, local hyperthermia (42 degrees C--43 degrees C), and ultrasonic hyperthermia results in increased cytotoxicity of chemotherapeutic drugs for the treatment of cancer. Human breast (MX-1) and lung (LX-1) tumors implanted subcutaneously in athymic nude mice were treated with a single application of ultrasonic (670 kHz, peak intensity of 5 watts/cm2) hyperthermia (43.0 degrees C +/- 0.5 degrees C) for 30 minutes in combination with suboptimal doses of cyclophosphamide, melphalan, or procarbazine. Delays in the tumor growth rate and temporary tumor regression were observed. Comparison of the tumor growth rate with single modalities, ie, drug or hyperthermia alone, shows evidence of synergistic effects of the combination of ultrasonic hyperthermia and melphalan on MX-1 and of hyperthermia and procarbazine on LX-1 tumors.