High-risk features were defined as age<40 at diagnosis, multifocal or multicentric tumors, triple-negative receptors (TN), presence of lymphovascular invasion (LVI), medial or central tumors, and high nuclear grade. The study Included 352 women who underwent mastectomy with T1-T2 N0i+ positive/N1mi breast cancer. Sixty percent (211) isolated tumor cells (ITCs), and 40% had micrometastases. Forty-six percent had only sentinel node biopsy (SNB), whereas 54% had axillary node dissection (ALND). Three hundred twenty-one did not undergo postmastectomy radiation (PMRT), and the study was confined to this group.
Only 11% had no high-risk features, whereas others had between one and four. SNB was performed in 151 patients (47%), while 170 patients (74%) had ALND. In patients with ITCs (196), 60% had SNB alone, while 40% had ALND. In patients with micrometastases (125), 26% had SNB alone, while 74% had ALND. All but 4% had chemotherapy, endocrine therapy, or both.
At a median follow-up of 6 years, only 9 (2.8%) of patients who did not undergo PMRT had a locoregional recurrence (LRR). The location of LRR in 8 cases was in the chest wall, while in 1 patient, it was in an internal mammary node. Nine percent of patients underwent PMRT. All of these patients had adjuvant systemic therapy. No LRR occurred in this group.
Using Kaplan-Meier estimation, there was no significant difference in LRR between those with or without PMRT. When considering SNB vs. ALND, the LRR rate was 3.7% and 1.6% (p=0.2), respectively.
In summary, in this patient population of T1-T2N0i+/N1mi treated with mastectomy, the LRR at 6% was only 2.8% at 6 years and with no axillary failures. The number of patients with high risk features in this study was too small to permit its impact on local recurrence.
This study from Memorial Sloan Kettering suggests that there is little benefit to axillary lymph node dissection or postmastectomy radiation therapy in women undergoing mastectomy for T1-T2N0i+/N1mi breast cancer.