Surgical Management of the Axilla in Patients with Occult Breast Cancer (cT0 N+) After Neoadjuvant Chemotherapy

Background: Occult breast cancer (OBC) is a rare clinical entity. Current surgical management includes axillary lymphadenectomy (ALND) with or without mastectomy. We sought to investigate the role of sentinel lymph node biopsy (SLNB) in patients with OBC treated with neoadjuvant chemotherapy (NAC). Methods: Patients with clinical T0N+ breast cancer were selected from the National Cancer Data Base (NCDB, 2004–2014) and compared according to axillary surgical approach, SLNB (≤ 4 LNs) or ALND (> 4 LNs). Primary outcome was overall survival (OS), calculated using Kaplan–Meier methods. Secondary outcome was complete pathological response (pCR). Results: A total of 684 patients with OBC were identified: 470 (68.7%) underwent surgery upfront and 214 (31.3%) received NAC. Of the NAC patients, 34 (15.9%) underwent SLNB and 180 (84.1%) ALND. One hundred and fifty-three (72%) patients received radiotherapy (RT). There was no difference in pCR rates between the ALND and SLNB (34.3% vs 24.5%, respectively p = 0.245). In patients undergoing surgery first, improved OS was observed with ALND compared to SLNB (106.9 vs 85.5 months, p = 0.013); however, no difference in OS was found in patients who received NAC (105.6 vs 111.3 months, p = 0.640). RT improved OS in patients who underwent NAC followed by SLNB (RT, 123 months vs no RT, 64 months, p = 0.034). Of NAC patients who did not undergo RT, ALND had superior survival compared to SLNB (113 vs 64 months, p = 0.013). Conclusion: This is the first comparative analysis assessing the surgical management of the axilla in patients with OBC who underwent NAC. In this population, there was a decrease in survival in patients who underwent SLNB alone; however, with the addition of RT, there was no difference in OS between SLNB and ALND. SLNB plus RT may be considered as an alternative to ALND in patients with OBC who have a good response to NAC.