Refining the prognostic significance of dna ploidy status in colorectal cancer: A prospective flow cytometric study

Abstract

A consecutive series of 123 colorectal cancers, prospectively followed for 3 years, was studied to determine if the prognostic significance of DNA ploidy related to: (a) thresholds used to define DNA aneuploidy, or (b) aneuploid sub‐groups defined by DNA index (DI) and peak size. Aneuploidy was defined using 3 methods depending on the minimum proportion of nuclei considered to constitute an aneuploid peak; type 1, 5%; type 2, 10%; type 3, 10% if Dl is 1.1–1.8, but 15% if Dl is 1.9–2.1. DNA aneuploidy rates were type 1, 75%; type 2, 67%; type 3, 58%. The significance of clinical and pathological correlations varied with the use of different methods. All were associated with a significant DNA diploid survival advantage which was strongest for type 3 (p=0.006). Dl was unrelated to survival irrespective of the presence or absence of an associated S/G₂; 33% with a Di of 1.1–1.8 and 35% with a Dl of 1.9–2.1 survived. Prognosis was inversely proportional to aneuploid peak size, 48% with small peaks (20%40%) survived (p=0.03). We conclude that: (a) thresholds used to define DNA aneuploidy affect the prognostic significance of DNA ploidy; (b) survival is independent of the Dl of aneuploid peaks; and (c) measurement of aneuploid peak size refines the prognostic value of DNA ploidy.