Hypoxic fractions in xenografted human colon tumors.

We investigated the percentage of radiobiologically hypoxic cells within 11 different xenografted human colon tumors using an in vivo-in vitro excision assay technique. Tumors were excised at average volumes of 750 mm3, and it was found that hypoxic fractions varied from less than 1% (clone D) to over 80% (HCT-8). The geometric mean hypoxic percentage was 10.4% (95% confidence interval, 4.9 to 22.1%). Comparison of the percentage of hypoxia results from the xenografted human colon tumors to published data from xenografted melanomas suggests that transplanted colorectal tumors as a class contain significantly less hypoxia than do the melanomas.