The synergistic effect of hyperthermia and chemotherapy on murine transitional cell carcinoma

The in vivo effect of hyperthermia and chemotherapy was studied in a murine transitional cell carcinoma model. Localized hyperthermia (43.5C) of 60 and 90 minutes duration was combined with systemic doxorubicin hydrochloride, cis-platinum, cyclophosphamide or mitomycin to treat tumors implanted into the hind legs of C3H mice. The data were compared to the results obtained from the application of hyperthermia or chemotherapy alone as well as to the natural growth rate of untreated tumors. Untreated tumors grew with an exponential rate and had a doubling time of 4 +/- 1.5 days. Animals bearing such tumors survived for 25 +/- 7 days. When treated with hyperthermia alone, there was no significant reduction in the growth rate and no improvement was noted in the survival time. Treatment with doxorubicin hydrochloride, cyclophosphamide or mitomycin administered alone was likewise not effective. Cis-platinum alone was able to induce a minimal decrease in the growth rate. When the administration of chemotherapy was accompanied by hyperthermia, significant synergistic effect was noted for doxorubicin hydrochloride, cis-platinum and cyclophosphamide (p less than .01); only the mitomycin and hyperthermia combination failed to improve survival and decrease the growth rate. The duration of the hyperthermia exposure influenced the degree of tumor response. Hyperthermia of 90 minutes duration resulted in consistently greater decrease in tumor growth rate with doxorubicin hydrochloride, cis-platinum or cyclophosphamide than 60 minutes of hyperthermia combined with the same agents. These results indicate that local hyperthermia combined with doxorubicin hydrochloride, cis-platinum or cyclophosphamide can induce tumor regression, increase tumor doubling time and improve the survival of the tumor-bearing animal. Only the hyperthermia-mitomycin combination did not result in significant improvement from the baseline values. Thus, hyperthermia combined with selected chemotherapeutic agents can have an adjuvant effect in the treatment of established, implanted mouse bladder tumors.