Kinetic parameters and the course of the disease in breast cancer.

The correlation between the labeling index (LI) of the primary mammary tumor and the course of the disease after initial treatment was studied prospectively on 128 patients. The surgical specimens of breast tumors were incubated in vitro with tritiated thymidine and autoradiographies were performed. Patients were treated by a simple mastectomy and axillary lymph nodes dissection; patients in whom one or more lymph nodes were found to be involved received postoperative radiotherapy. None of the patients received adjuvant chemotherapy. As the LIs were not known at the time of treatment, their values did not influence the choice of therapy. The follow-up period is greater than six years for all patients. The higher the LI, the shorter were the time intervals from initial treatment to first relapse or from first relapse to death. Moreover, significant correlations were found between the LI and the relapse-free survival and the survival rates. The proportion of relapses was particularly small in the group with the low LI. The shape of the curve suggests that the outcome in this group will be better than that in the group with a high or a median LI. The LI kept its prognostic value after multiple adjustments for other prognostic factors such as the staging, the size of the tumor, the number of metastasis bearing axillary lymph nodes, the presence of an inflammatory reaction, and hormonal status. The LI is significantly correlated with the histologic grading and in particular with its mitotic components. Thus, proliferative activity assessed by LI or the mitotic index appears to provide significant independent prognostic information.