Epinephrine or peplomycin combined with hyperthermia in irradiated Lewis lung carcinoma: effects on tumor growth, skin reaction, and lung metastasis.

Although hyperthermia potentiates the effect of radiation, the combined effect decreases as the time between irradiation and hyperthermia increases. The purpose of this study was to prevent the rapid loss of efficacy by the local injection of epinephrine or peplomycin(PEP), two agents known as hyperthermic potentiators. In this study, Lewis lung carcinoma implanted in the foot of BDF1 mice was used for the assessment of tumor growth, skin reactions, and lung metastasis. The tumors were irradiated, then warmed in a water bath for 45 min. The retarding effects of hyperthermia on tumor growth and skin reactions were lost 2 days after irradiation. However, when PEP or epinephrine was injected before hyperthermia, tumor growth was distinctly delayed. The effect of epinephrine was greater than PEP and still showed enhancement 8 days after irradiation. For skin reactions, no significant enhancing effect was observed. Lung metastasis was significantly inhibited by the addition of epinephrine either 0 or 2 days after irradiation. In conclusion, the local administration of epinephrine combined with hyperthermia significantly retarded tumor growth without an increase in skin reactions or lung metastases. Possible mechanism underlying this phenomenon was discussed.