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The clinicopathologic staging of colorectal cancer is the subject of recent debate. We studied morphologic variables in a series of tumors resected from 284 patients. Half had been prospectively, randomly allocated to receive a 4-day schedule of preoperative pelvic radiotherapy followed by immediate surgery. There was a significant (P less than 0.01) difference in the distribution of tumors of various histopathologic grades between irradiated (XS) and unirradiated (S) patients and borderline differences in the predictive values of venous spread, tumor grading, and local spread. However, these differences were less marked in 180 tumors examined by one review pathologist. They were thought to be due to misinterpretation of changes induced by radiotherapy. No differences were detected in the distribution of tumors of various sizes and Dukes' stage in the XS and S groups. The review pathologist recorded a borderline (P = 0.049) difference in the distribution of tumors of various CEA staining patterns between the XS and S groups. In a Cox regression model. Dukes' staging remained the most important predictive variable for survival and pelvic recurrence in the XS and S groups. Dukes' staging was apparently unchanged by this schedule of preoperative radiotherapy, but Broders' grading may be unreliable. Any new clinicopathologic staging system for colorectal cancer should record when preoperative radiotherapy is delivered. More studies of radiotherapy effects are required.

DNA extracted from 31 primary colorectal carcinomas was analyzed for the presence of ras gene amplification and mutations. Nine carcinomas had Ha-ras amplification and seven Ki-ras amplification. Nine carcinomas had codon 12 Ki-ras mutations. Immunohistochemical staining for ras proteins revealed a normal membrane association in normal mucosa and benign polyps but an abnormal cytoplasmic distribution in carcinomas. Amplification, mutations, and immunohistochemical staining were independent of histologic differentiation, Dukes' stage, or DNA ploidy status. This study demonstrates that abnormalities of ras genes are a common finding in colorectal carcinomas. They are potentially important biologic changes associated with malignancy, although they do not appear to be related to clinical behavior.