S-phase fractions of colorectal carcinomas related to pathologic and clinical features

The S-phase fractions (SPFs) of epithelial cells in 100 resected colorectal carcinomas were measured by in vitro exposure to tritiated thymidine and autoradiography. The frequency distribution of SPFs was gaussian with a median of 17.8 per hundred in 90 unirradiated carcinomas, whereas in ten carcinomas given radiation therapy preoperatively, it was positively skewed with a median of 6.9. Analysis of the unirradiated carcinomas showed no relationship between SPF and various clinical and morphologic features that included age, race, sex, site, size, Dukes' stage, histologic grade of the tumor, number of metastasis-bearing regional lymph nodes, presence of adenomas of the large bowel, survival or relapse-free survival of the patient, or SPF or adjacent normal colorectal crypts. The results show no evidence that colorectal carcinomas can be divided into kinetic subsets. The spatial orientation of labeled cells in autoradiographs indicated presence of a nonproliferative fraction of cells in many tumors that may modulate response to radiation therapy and chemotherapy.