In vitro autoradiographic determination of cell kinetic parameters in adenocarcinomas and adjacent healthy mucosa of the human colon and rectum.

Using in vitro double labeling with two different doses of [3H]thymidine, we measured the S-phase duration and the labeling index in biopsy samples taken from human rectal and colonic adenocarcinomas. Samples from the adjacent healthy mucosa, taken at the same time as the tumor samples, were simultaneously subjected to the same measurements. The mean labeling index in tumors was higher than in the normal mucosa (32.5 and 17.0%, respectively). The mean S-phase value was also longer than in the normal tissue (19.4 versus 11.2 hr). These observations are discussed with reference to similar observations made in tumors of the human epidermis, especially considering the possible relationship of an increased S-phase duration with carcinogenesis. While no definitive conclusions may be reached, it seems prudent to consider an S-phase duration that is longer than normal to be a justification for attentive follow-up of the patient.