Outcomes of Stage I and II Breast Cancer with Nodal Micrometastases Treated with Mastectomy without Axillary Therapy.

Purpose: Studies that report equivalent oncologic outcomes of sentinel lymph node biopsy (SLNB) alone versus axillary lymph node dissection (ALND) for T1-2N1mi breast cancers are heavily weighted with patients who received breast-conserving surgery (BCS). The impact of omitting ALND in N1mi patients treated with mastectomy is not well studied. It is also unknown if these patients would benefit from post-mastectomy radiotherapy (PMRT). This study reports the outcomes of patients with T1-2N1mi breast cancer treated by mastectomy without axillary therapy.

Methods: Patients who had T1-2N1mi breast cancer and underwent mastectomy from January 1998 to December 2018 were identified from our multi-institutional prospective database. Axillary recurrence rate (ARR), disease-free survival (DFS), and overall survival (OS) are reported.

Results: 260 patients with pT1-2N1mi breast cancer who had mastectomy were identified. They had either SLNB (35.4%) or ALND (64.6%). Majority of these patients received adjuvant systemic therapy (93.8%). 77 (29.6%) patients received radiotherapy, 31 after SLNB and 46 after ALND. At median follow-up of 61 months, ARR was 1.1% (n = 1) in the SLNB only group, vs. 0.6% (n = 1) in the ALND group (p = 0.752). DFS and OS were not significantly different between patients with SLNB alone versus ALND (p = 0.40 and p = 0.27, respectively). Among 92 patients who had SLNB only, no DFS or OS difference was observed with the use of PMRT.

Conclusion: In T1-2N1mi patients with mastectomy and SLNB, axillary recurrences were rare. No statistically significant differences were noted between patients with SLNB, ALND, or PMRT. Our findings suggest that these patients may be safely treated without axillary therapy.