Prospective study on prognostic significance of DNA ploidy and Ki-67 expression in colorectal cancer

Abstract

21184 Background: The prognostic value of flow cytometry DNA ploidy and Ki-67 expression in colorectal carcinomas has not been defined yet. The study tries to correlate tumoral DNA ploidy and proliferative activity (Ki-67) with therapy response, Overall Survival (OS), Disesase Specific Survival (DSS) and Disease Free Survival (DFS). Methods: From 01/09/02 to 30/06/05, 3 samples of cancer tissue and 1 sample of normal mucosa has been collected from all operating pieces of colorectal cancer. These samples were frosen and later disgregated, treated and coloured with Propidium Iodide. DNA ploidy was evaluated by FACSCalibur cytofluorimetry. Normal mucosa tissue was our internal control. Ki-67 was evaluated by immuno-histochemistry in all tumoral samples. All the patients were cured with chemo- and/or radiotherapy in our divisions. Results: 67 patients (M/F 35/32); median age was 70; staging: 19% I, 33% II, 30% III, 18% IV. We found aneuploidy in 65,7% of carcinoma and Ki-67 median expression was 55%. DNA tumoral heterogeneity was present in 27% of patients. DNA aneuploidy correlates with advanced disease stage at diagnosis (p<0,01), with high number of metastatic lymphnodes (p<0,005) and with serological markers positivity (p<0,04). After surgery and chemotherapy 35% of the patients with aneuploid carcinoma and high proliferative activity (Ki-67>55%) do not show evident disease versus 100% of patients with DNA diploidy and lower Ki-67. Tumoral aneuploidy correlates in a significative way with lower OS (48% vs 89% of diploid patients), lower DSS (tumor death happened just in patients with aneuploid DNA in every disease stages), with lower DFS (18% vs 86% of diploid patients). Univariated analysis stated that aneuploidy determinates an Odd Ratio=5,7 to develop disease progression (p=0,033). At the moment Ki-67 expression with 55% cut-off does not seem to correlate with OS, DSS and DFS. Conclusions: Preliminar results (the study is still in progress) seem to suggest that cytofluorimetric DNA-ploidy has a prognostic and predictive significance in colo-rectal carcinomas. Ki-67 expression (immuno-histochemistry) has an uncertain significance. The small number of patients and the short follow-up do not allow us to reach any definitive conclusions, but the study is worth to go on. No significant financial relationships to disclose.