Association between extent of axillary lymph node dissection and survival in patients with stage I breast cancer.

BACKGROUND: The role of axillary lymph node dissection for stage I (T1N0) breast cancer remains controversial because patients can receive adjuvant chemotherapy regardless of their nodal status and because its therapeutic benefit is in question. The purpose of this study was to determine whether extent of axillary dissection in patients with T1N0 disease is associated with survival.

METHODS: Data from 464 patients with T1N0 breast cancer who underwent axillary dissection from 1973 to 1994 were examined retrospectively. Kaplan-Meier estimates of overall survival, disease-free survival, and recurrence were calculated for patients according to the number of lymph nodes removed (<10 or > or = 10; <15 or > or = 15), and survival curves compared using the Wilcoxon-Gehan statistic. Cox proportional hazards regression modelling was used to adjust for confounding prognostic variables.

RESULTS: Median follow-up time was 6.4 years. Patient groups were similar in age, menopausal status, tumor size, hormonal receptor status, type of surgery, and adjuvant therapy. There was a statistically significant improvement in disease-free survival in the > or = 10 versus <10 nodal groups (P <.01). Five-year estimates of survival were 75.7% and 86.2% for <10 nodes and > or = 10 nodes, respectively; 10-year estimates were 66.1% and 74.3%. There also was a notable improvement in the survival comparison of patients with <15 versus > or = 15 nodes (P < or = .05). These findings were confirmed in the multivariate analysis.

CONCLUSIONS: These results may reflect a potential for misclassification of tumor stage among patients who had fewer nodes removed. The data, however, suggest that in patients with Stage I breast cancer, improved survival is associated with a more complete axillary lymph node dissection.