In vitro chemotherapy sensitivity testing of primary human colorectal carcinomas.

The cells obtained from 138 tumor samples taken from 135 patients with colorectal malignancies were cultured in vitro in a soft agar colony formation assay similar to that of Salmon and colleagues [1]. Significant colony formation occurred for 63 (51%) of evaluable tumor cultures, 53 of which were also tested against chemotherapeutic agents in vitro. The median number of drugs tested per tumor was 15. Using 70% inhibition of colony formation as the criterion for significant drug-induced cytotoxicity, only 3/53 (6%) of the tumors were noted to be sensitive to any drug. When colony counts generated by initially plated small tumor cell aggregates were taken into account, 8/40 (20%) of the tumors were noted to be sensitive in vitro to one or more agents. Because of the low rate of drug sensitivity found with this in vitro assay, its current role in the prospective assignment of chemotherapeutic treatment for patients with colorectal carcinoma is somewhat limited.