Thermochemosensitivity: augmentation by hyperthermia of cytotoxicity of anticancer drugs against human colorectal cancers, measured by the human tumor clonogenic assay.

Thermochemosensitivity was examined in vitro by a human tumor clonogenic assay (HTCA) using specimens obtained surgically from 43 patients with colorectal cancer. We found that the percentages of patients whose cells showed higher sensitivity (greater than 70% inhibition of colony formation) to hyperthermia alone were 29.6 and 55.6% at 42 and 43 degrees C each for 1 h, respectively. Similarly, percentages of patients whose cells were sensitive to drugs alone were 13.8, 24.1 and 48.3%, for cis-diamminedichloroplatinum(II), 5-fluorouracil and mitomycin C, respectively. These sensitivities were augmented when hyperthermia was combined with administration of anticancer agents. Even in tumor cells that were insensitive to anticancer drugs alone or to hyperthermia alone, sensitivity was enhanced when administration of drugs was combined with hyperthermia. Our results demonstrate that HTCA of tumor cells, obtained from suitable patients, may be useful as a predictive test for application of thermotherapy and for individualization of chemotherapy.