Factors affecting relapse in node-negative breast cancer. A multivariate analysis including the labeling index.

Between 1975 and 1982, 167 patients with carcinoma of the breast without axillary lymph node metastases were studied. The thymidine labeling index (LI), representing the percentage of cells in the DNA synthesis phase, was measured in all these patients. High LI values were more frequently encountered in young patients (P = 0.05), in low estrogen receptor (ER) tumor content (P = 0.007) and in high grade tumors (P = 0.0002). The overall 8-year relapse-free survival (RFS) was 68%. Univariate analysis demonstrated that RFS was influenced by histological grading (P = 0.03), ER (P = 0.03), PR (P = 0.02) and LI (P = 0.01). Multivariate analysis using the Cox regression model selected the LI as the single significant prognostic factor with regard to RFS (P = 0.037). These results emphasize the important role of cell proliferation kinetics in defining node-negative breast cancer patients with a high risk of relapse.