Cell kinetics evaluation of colorectal tumors after in vivo administration of bromodeoxyuridine.

Although several biomarkers have been tested, Dukes' (or TNM) stage at diagnosis is still considered the only prognostic factor of clinical relevance in colorectal cancer. Among the various biomarkers, the fraction of cells engaged in DNA synthesis has been extensively investigated as an indicator of tumor aggressiveness. Bromodeoxyuridine (BUdR) is a non-radioactive thymidine analogue which is incorporated into DNA during the S-phase of cycling cells. In order to evaluate the relationships between cell kinetics and morphologic variables, 500 mg of BUdR were given i.v. to 46 patients with colorectal cancer prior to surgery. After operation, a large tumor sample was taken and processed for immunohistochemical detection of BUdR-labeled cells in various regions of the neoplasm and in normal colorectal mucosa. Smaller superficial tumor specimens were also incubated with 3H-thymidine (3H-TdR) for the autoradiographic identification of labeled cells. In the 43 evaluable tumors, the overall BUdR labeling index (BLI, percent of labeled cells) was significantly higher in carcinoma (20.30 +/- 0.86%, SEM) than in normal colonic mucosa (6.51 +/- 0.49%). BLIs in central and peripheral regions of carcinoma were closely correlated (r = 0.48, p = 0.003). In 21 neoplasms a high correlation between overall BUdR and 3H-TdR labeling index in the same tumor was observed (r = 0.57, p = 0.007). No evident association between overall BLI and clinical or morphologic parameters of the tumor was seen, including number of capillaries and ras-p21 protein expression. We conclude that BUdR immunostaining after in vivo administration of BUdR is a simple method for studying cell kinetics in various regions of colorectal cancer. BUdR labeling data are comparable to those obtained with in vitro incorporation of 3H-TdR.