Significance of micrometastases on the survival of women with T1 breast cancer

BACKGROUND. The most important factor in predicting survival among women with newly diagnosed breast cancer is the status of the axillary lymph nodes. Although straightforward to define, the impact of micrometastases on survival remains to be completely determined. METHODS. A review of data from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute was performed using 43,921 cases diagnosed from January 1988 through December 2001. Among women with invasive breast carcinomas <= 2 cm undergoing a resection of the primary malignancy and an axillary lymph node dissection, there were 42,197 cases without lymph node metastases and 1724 cases with micrometastases. Survival differences among these 2 groups were evaluated and are reported here. RESULTS. Survival at 12 years was modestly affected by the presence of either solitary (5.0%) or multiple lymph nodes (3.6%) with micrometastases when compared with lymph node-negative cases. In subgroup analyses, the decreased survival associated with micrometastases was inconsistent. The most significant survival disadvantage associated with micrometastases was found in cases with Grade 3 carcinomas. CONCLUSIONS. The modest and variable impact of micrometastases on long-term survival indicates that micrometastases are an important, but not a dominant, prognostic indicator.