Interaction of Hyperthermia and Photoradiation Therapy

Abstract

Local microwave hyperthermia (2450 MHz) was applied to axillary implants of the SMT-F mammary carcinoma in mice in combination with photoradiation therapy (PRT) in an attempt to determine if the 2 modalities interact. When 40.5.degree. C was applied for 30 min immediately prior to or immediately following PRT (630-nm light, 30 min, at 75 mW/cm2, 20-24 h post 7.5 mg/kg hematoporphyrin derivative), enhancement of tumor response over that of PRT alone was seen as judged by lack of tumor regrowth (35 days or longer after treatment). A temperature of 41.5.degree. C applied for 30 min immediately following the 30 min PRT treatment produced a result slightly greater than that seen at 40.5.degree. C. When a temperature of 44.5.degree. C for 30 min was applied immediately following PRT, a substantial enhancement of tumor control at 35 days post-treatment was found (53% vs. 19 and 4%, respectively, for hyperthermia and PRT alone). Tumor response to PRT apparently is enhanced by both a sublethal hyperthermic treatment (40.5.degree., 41.5.degree. C) and a moderately lethal heat treatment (44.5.degree. C) given for a short duration, when applied immediately before or after photoradiation.