Observational study of axilla treatment for breast cancer patients with 1-3 positive micrometastases or macrometastases in sentinel lymph nodes.

Sentinel node biopsy is a standard procedure in clinically node-negative breast cancer patients. It has eliminated unnecessary axillary lymph node dissection in more than half of the early breast cancers. However, one of the unresolved issues in sentinel node biopsy is how to manage axilla surgery for sentinel node-positive patients and clinically node-negative patients. To evaluate the outcome of no axillary lymph node dissection in sentinel node-positive breast cancer, a prospective cohort study registering early breast cancer patients with positive sentinel nodes has been conducted (UMIN 000011782). Patients with 1-3 positive micrometastases or macrometastases in sentinel lymph nodes are eligible for the study. The primary endpoint is the recurrence rate of regional lymph nodes in patients treated with sentinel node biopsy. Patients treated with sentinel node biopsy followed by axillary lymph node dissection are also registered simultaneously to compare the prognosis. The propensity score matching is used to make the distributions of baseline risk factors comparable.