Thermally-enhanced tumor regression in mice treated with melphalan.

Mice were implanted subcutaneously with one of three types of tumor, each isogeneic to the respective host. These were two mammary adenocarcinomas designated DBAH and MT2, and a spindle cell sarcoma designated TEC. Tumor-bearing mice were treated with melphalan alone, locally-applied microwave hyperthermia alone (42-43 degrees C) or with a combination of these two modalities. Following treatment, tumor growth and regression, and survival of host were recorded. Only mice bearing the DBAH tumor were cured by either modality alone. The MT2 and TEC tumors responded only slightly to melphalan treatment alone. Approximately half of the TEC tumors responded to prolonged treatment by hyperthermia alone, yielding total regressions; the MT2 tumor proved to be resistant to this modality. Doses of hyperthermia which had no effect on tumor growth when applied alone were able to induce a thermal potentiation of melphalan. All 3 tumor types were cured by this combined treatment, although different doses of hyperthermia were required for each tumor type.