Analytical DNA flow cytometric analysis of colorectal cancer: prognostic and biological implications

Abstract

To determine the biological and prognostic significance of DNA ploidy, 492 consecutive and prospectively documented cases of colorectal cancer were retrieved from the archives of Concord Hospital. 35 cases were excluded due to poor preparations. Nuclei were extracted from paraffin blocks and analysed by DNA flow cytometry. A tumour was classified as diploid when only one G 0 -G 1 peak was detected and aneuploid when there were two or more G 0 -G 1 peaks. The DNA index (DI) was derived from the ratio between the mean fluorescence intensities of the second or aberrant G 0 -G 1 peak and the reference 2N peak. Anatomical Site Diploid Hyperdiploid DI DI ≥ 1.4 Proximal Colon 58 27 37 Distal Colon 56 25 81 Rectum 67 26 80 After a follow-up of 7 years DNA ploidy was of marginal importance as a prognostic indicator (p=0.055). Clinical staging (ACPS), extent of direct tumour spread and extent of lymph node involvement were the most relevant prognostic indicators, once other factors were taken into account. Aneuploidy was also significantly correlated with absence of contiguous adenoma, tumour ulceration and venous invasion. The degree of aneuploidy or DI was greater in distal colorectal (DCR) i.e. splenic flexure and beyond than proximal colon (PC) cancers (p