TUMOR LABELING INDEXES OF PRIMARY BREAST CANCERS AND THEIR REGIONAL LYMPH-NODE METASTASES

Background. Tumor labeling index has emerged as a strong predictor of the clinical course of women with breast cancer. This study investigat ed whether labeling index of primary tumors correlates with labeling i ndices of concurrent regional node metastases. Methods. With appropria te written consent, preoperative in vivo infusion of the thymidine ana logue 5-bromodeoxyuridine (BrdUrd) was used to label 109 human breast cancers. Labeled S-phase cells were identified immunohistochemically w ith an antibody specific to DNA-incorporated BrdUrd. Labeling index wa s the fraction of labeled nuclei in 2000 tumor nuclei. For 30 women, t here was sufficient cancer in axillary lymph nodes to compare labeling indices in primary breast cancer and regional lymph node metastases. Results. The 30 women were from 25 to 82 years of age. Tumors were fro m 1 to 12 cm in size and there were from 1 to 26 positive nodes. Tumor labeling index ranged from 0.1% to 34%, (mean, 11.1%; median, 10.3%) and axillary lymph node metastasis labeling index ranged from 0.1% to 27.7% (mean, 10.8%; median. 10.0%). There was strong correlation betwe en primary tumor labeling index and regional lymph node metastases lab eling index (r = 0.82, with 95% confidence interval 0.65-0.91). The co rrelation persisted within subgroups according to age, tumor size, num ber of positive nodes, and hormone receptor status. Primary tumor and lymph node metastases labeling indices also had statistically similar relationships with age, level of hormone receptors, tumor size, and nu mber of positive nodes. Conclusions. Primary tumor and regional node l abeling indices correlate strongly; the relationship is not influenced by age. level of hormone receptors, tumor size, or number of positive nodes.