In vitro growth ability and chemosensitivity of gastric and colorectal cancer cells assessed with the human tumour clonogenic assay and the thymidine incorporation assay.

A human tumour cloning assay (HTCA) has been performed on 191 samples of gastric and 152 samples of colorectal cancers, and a thymidine incorporation assay (TIA) on 178 samples of gastric and 109 samples of colorectal cancers. The rate of evaluable assays was significantly higher in the TIA than in the HTCA (P less than 0.01). In terms of in vitro growth potential in the two assays, gastric cancer cells were less active than the colorectal cancer cells (P less than 0.05). In frequency of in vitro sensitivity to drugs, gastric cancer was more chemosensitive than colorectal cancer in both assays. The in vitro/in vivo correlations of high resistance-predictive ratios and low sensitivity-predictive ratios were similar in both assays. The results indicate that the TIA is more applicable than the HTCA to screening of active agents against fresh gastrointestinal cancers.