Thymidine labeling index in colorectal carcinoma: relation to clinicopathological parameters and to mitotic index

Two cell-kinetic parameters, the thymidine labeling index (T-LI) and the mitotic index (MI) were determined for a prospective series of 74 primary colorectal cancers. Dukes' stages were used to define the extent of the tumor: 10 tumors were classified as Dukes' A, 36 as Dukes' B, and 22 as Dukes' C. Of these tumors, 14 were well-differentiated, 44 moderately differentiated, and 15 poorly differentiated adenocarcinomas. The H3dT-LI values obtained varied widely, from 2.5 to 38.9% (median value: 16.8%). The MI shows a range of from 0 to 13.2% with a median value of 3.2%. The T-LI values were independent of the sex and age of the patients and of the histological grading and Dukes' stage. Conversely, the MI was related to histological grading. This study indicates that the T-LI, whose application has reached the gold standard, still represents an independent parameter and the most sensible, objective, and specific complementary method for the analysis of the S phase.