Prognostic value of DNA ploidy status in patients with rectal cancer

Abstract

Background: A retrospective study was performed to measure the prognostic value of DNA ploidy status and proliferative index (PI) for survival in patients with rectal cancer.

Patients and methods: Fifty-two patients underwent curative surgery for rectal carcinoma. Ten tumors were in Stage I, 25 cancers were in Stage II, and 17 of them were in Stage III. Using flow cytometry the nuclear DNA content of the tumor cells was measured.

Results: There were 25 DNA diploid and 27 DNA aneuploid carcinomas. Aneuploid DNA content did not show higher occurrence in advanced tumors. The mean survival was 59 months in the case of DNA diploid carcinoma, while it was 47 months in the case of DNA aneuploid cancer. The mean PI of the DNA diploid cancers was 8%. The PI of DNA aneuploid tumors was 22%. High PI (PI > 10%) was observed in 32 carcinomas while low PI (PI < 10%) occurred in 20 cases. Patients with aneuploid DNA content and high PI had significantly worse survival compared to patients with diploid DNA content while low PI. Locoregional and distant metastases occurred more frequently in patients with aneuploid tumor. By univariate analysis, tumor size, lymph node involvement, DNA ploidy status and PI all correlated with prognosis. However, multivariate analysis showed that TNM stage and PI were the only significant prognostic factors for survival.

Conclusion: The survival and disease-free survival of patients with diploid DNA content was better compared to aneuploid cases. The results suggest that DNA ploidy status is important in determining the biological behaviour of rectal carcinomas, although the multivariate analysis did not prove its significant influence. The PI were independent negative prognostic factors for survival.