Prognostic value of DNA content in colorectal carcinoma. A flow cytometric study with some methodologic aspects.

The DNA content of 37 colorectal carcinomas was studied prospectively by flow cytometry. The DNA content from the same tumors was also studied in disintegrated paraffin sections. The methods gave similar information on the DNA content and the correlation was 0.94. In eight patients tumor imprints were prepared and the DNA content was analyzed with static cytometry. A correlation coefficient of 0.83 between flow cytometry on fresh tumor tissue and static cytometry was found. Sixty-two percent of the tumors were aneuploid and had significantly higher S-phase values than diploid tumors. Histologic grade was not related to ploidy level, whereas Dukes' C tumors often were aneuploid. When the clinical course of patients was analyzed by log rank test (mean follow-up, 30.4 months), the patients with diploid tumors showed a clear advantage in terms of survival; only two patients in this group developed progressive disease. It is concluded that the DNA content is an independent prognostic predictor of colorectal carcinoma and that DNA can be analyzed by several methods. Of these, the method using disintegrated paraffin sections appears most attractive.