Background: Sentinel lymph node biopsy is an established staging method in early breast cancer. After a negative biopsy, most institutions will not perform a completion axillary dissection. The present study reports the current axillary recurrence (AR) rate, overall and disease-free survival in the Swedish Multicenter Cohort Study.

Methods: From 3534 patients with primary breast cancer ≤3 cm prospectively enrolled in the Swedish multicenter cohort study, 2246 with a negative sentinel node biopsy and no further axillary surgery were selected. Follow-up consisted of annual clinical examination and mammography. Twenty-six hospitals and 131 surgeons contributed to patient accrual.

Results: After a median follow-up time of 37 months (0-75), the axilla was the sole initial site of recurrence in 13 patients (13 of 2246, 0.6%). In another 7 patients, axillary relapse occurred after or concurrently with a local recurrence in the breast, and in a further 7 cases, it coincided with distant or extra-axillary lymphatic metastases. Thus, a total of 27 ARs were identified (27 of 2246, 1.2%). The overall 5-year survival was 91.6% and disease-free survival 92.1%.

Conclusions: This is the first report from a national multicenter study that covers, not only highly specialized institutions but also small community hospitals with just a few procedures per year. Despite this heterogeneous background, the results lie well within the range of AR rates published internationally (0%-3.6%). The sentinel node biopsy procedure seems to be safe in a multicenter setting. Nevertheless, long-term follow-up data should be awaited before firm conclusions are drawn.