Long‐term prognosis in breast cancer is associated with residual disease after neoadjuvant systemic therapy but not with initial nodal status

BACKGROUND: This follow‐up analysis of a Swedish prospective multicentre trial had the primary aim to determine invasive disease‐free (IDFS), breast cancer‐specific (BCSS) and overall survival (OS) rates, and their association with axillary staging results before and after neoadjuvant systemic therapy for breast cancer. METHODS: Women who underwent neoadjuvant systemic therapy for clinically node‐positive (cN+) or ‐negative (cN0) primary breast cancer between 2010 and 2015 were included. Patients had a sentinel lymph node biopsy before and/or after neoadjuvant systemic therapy, and all underwent completion axillary lymph node dissection. Follow‐up was until February 2019. The main outcome measures were IDFS, BCSS and OS. Univariable and multivariable Cox regression analyses were used to identify independent factors associated with survival. RESULTS: The study included a total of 417 women. Median follow‐up was 48 (range 7–114) months. Nodal status after neoadjuvant systemic therapy, but not before, was significantly associated with crude survival: residual nodal disease (ypN+) resulted in a significantly shorter 5‐year OS compared with a complete nodal response (ypN0) (83·3 versus 91·0 per cent; P = 0·017). The agreement between breast (ypT) and nodal (ypN) status after neoadjuvant systemic therapy was high, and more so in patients with cN0 tumours (64 of 66, 97 per cent) than those with cN+ disease (49 of 60, 82 per cent) (P = 0·005). In multivariable analysis, ypN0 (hazard ratio 0·41, 95 per cent c.i. 0·22 to 0·74; P = 0·003) and local radiotherapy (hazard ratio 0·23, 0·08 to 0·64; P = 0·005) were associated with improved IDFS, and triple‐negative molecular subtype with worse IDFS. CONCLUSION: The present findings underline the prognostic significance of nodal status after neoadjuvant systemic therapy. This confirms the clinical value of surgical axillary staging after neoadjuvant systemic therapy.