DNA index as a significant predictor of recurrence in colorectal cancer

To clarify the prognostic significance of the DNA content in cases of colorectal cancer, we investigated the relationship between the DNA content, as determined by the DNA ploidy or DNA index, and disease-free survival.

This study included 201 cases that were treated by curative surgery between 1989 and 1995 at our hospital. 68 were diploid and 133 were aneuploid. The mean DNA index of these tumors was 1.42. Recurrence occurred in 30 cases (14.9 percent). Tumor site, venous invasion, Dukes stage, DNA ploidy (diploid or aneuploid), and a DNA index (less than or greater than 1.4) correlated well with disease-free survival. A multivariable analysis suggested the DNA index to be a stronger predictor than DNA ploidy. Patients with aneuploid tumors had shorter disease-free survival than those with diploid tumors (P = 0.011), especially in Dukes Stage C cases (P = 0.0209). Patients with a DNA index greater than 1.4 also had a shorter disease-free survival than those with a DNA index less than 1.4 (P < 0.001), especially in Dukes Stage C cases (P = 0.0033).

The DNA index value (less than or greater than 1.4) seems to be a stronger predictor than DNA ploidy (diploid or aneuploid), and the combination of Dukes stage, tumor site, and a DNA index is, therefore, considered to be clinically valuable in predicting recurrence in cases of colorectal cancer.