Local regional management of the axilla after positive sentinel node biopsy in breast cancer patients clinically downstaged with neoadjuvant therapy: A population-based, real-world analysis.

Abstract

e12578 Background: The optimal local regional management of the positive axilla in patients who convert to clinical negative nodal status after neoadjuvant chemotherapy (NAC) remains unclear. Specifically, the benefit of completion axillary node dissection (cALND) remains in question, particularly given the associated morbidity. With results of the A11202 trial pending, we noted regional variation in the management of the axilla in this population. We therefore aimed to describe the current management of women with positive SNB after NAC, describe recurrence patterns and identify predictors of cALND in a large, population-based, real-world setting. Methods: We identified all patients who had biopsy-proven nodal disease on presentation, underwent NAC and were then clinically downstaged allowing SNB as part of their index surgery from our Synoptec provincial operative database, from January 2016 to September 2021. Pre and post NAC tumour characteristics, patient demographics, treatments and final pathology were abstracted and conveyed using descriptive statistics. Primary outcome measures were treatment with cALND and recurrence. A Cox regression model was utilized to determine predictors of both outcomes. Results: A total of 850 patients had biopsy-proven axillary disease at presentation and subsequently underwent NAC. Of these, 364 patients converted to clinically-negative node status and had a SNB, of which 175 (48%) had persistent nodal disease. Median age of this group was 50 (IQR 43-60) and 143 patients (81.7%) were treated by a high-volume breast surgeon. Most patients had clinical T1/2 tumours (73.1%) before NAC, of which 21.1% were HER2 positive, and 12.6% were triple-negative. Post NAC, 95 patients (54.3%) underwent mastectomy. A total of 39/175 patients (22.3%) underwent a cALND. Median number of sentinel nodes was 4 (IQR 3, 5); the proportion of positive sentinel nodes did not differ in those who had cALND (0.59 vs. 0.59, p = 0.95). Almost all patients (96.6%) had regional radiation. After a median of 17 months of follow-up, 33 (18.8%) SNB positive patients recurred; the majority (29 (87.9%)) had a distant recurrence, 3 (9.1%) had an isolated local breast/chest wall recurrence, and only 1 (3.0%) had an isolated regional recurrence. As far as local control, in patients with any regional recurrence, 4/7 (57.1%) had undergone cALND. Treatment site was the only significant predictor of cALND on multivariable analysis. Predictors of recurrence were low BMI, triple-negative status and clinical T3/4 disease before NAC. Conclusions: The lack of definitive data for patients with persistent pathologic nodal disease after NAC has led to variable practice patterns, with lower than expected rates of cALND. Within our cohort, there was not a significant association between omission of cALND and regional recurrence.