[Current status of the human tumor clonogenic assay for gastrointestinal cancer]

The author reviewed his experience to date with chemosensitivity testing of 162 gastric and 144 colorectal cancers. All human tumor clonogenic assays were performed using a double-layer soft agar system with continuous exposure of cells to one concentration of standard anticancer drugs. Significant growth was defined as greater than or equal to 30 colonies/control plate. Clinical responses were determined according to standard criteria. Forty-six per cent of gastric cancer specimens and 67% of colorectal cancer specimens plated produced significant growth in vitro. When greater than or equal to 50% inhibition of colony formation was used as the criterion for differentiating sensitivity from resistance, the assay was 67% (8/12) reliable for predicting in vivo sensitivity, and 91% (10/11) reliable for in vivo resistance.