Post neoadjuvant chemotherapy vacuum assisted biopsy in breast cancer: Can it determine pathologic complete response before surgery?

Abstract

567 Background: Neoadjuvant chemotherapy (NAC) is increasingly used in phenotype appropriate early operable breast cancer. Pathologic complete response (pCR) rates of up to 60% have been reported, suggesting that a proportion of patients may require less or even no surgery. In our practice, image-guided vacuum assisted biopsy (VAB) has been used after completion of NAC to assess residual disease and facilitate risk-adaptive surgery. The aim of this analysis was to investigate if post-NAC VAB could reliably identify exceptional responders who may not require surgical intervention. Methods: Retrospective cohort study of breast cancer patients treated with NAC, who had partial/complete imaging response and underwent post-NAC VAB to aid surgical planning, between 01/2013 and 01/2018. pCR was defined as no residual disease in the breast (ypT0). Diagnostic accuracy of VAB was calculated using final surgical pathology as the reference standard. Simple descriptive statistics and nonparametric analyses were performed. Results: 53 patients underwent post-NAC VAB. The overall pCR rate was 41.5% [53.8% for HER2 positive, 72.7% for triple negative (TN) phenotypes]. The post-NAC VAB false negative rate (FNR) was 19.4% (95% CI: 5.5-34.5) and the negative predictive value (NPV) was 76.9% (95% CI: 60.7-93.1) with an overall accuracy of 84.9% (95% CI: 75.3-94.5). Subgroup analysis showed that post-NAC VAB performed best in the TN group (n = 11) [FNR: 0%, NPV: 100%, overall accuracy: 90.9% (95% CI: 73.9-100)]. No significant associations were identified between tumor and technique characteristics and diagnostic performance of VAB. Conclusions: Our data suggest that post-NAC VAB may reliably predict pCR in patients with TN breast cancer. However, its diagnostic accuracy was not maintained across all phenotypes. Refinements and standardization in patient selection and VAB technique and more prospective trials are warranted to further explore the role of post-NAC VAB in supporting minimal or no surgery trials.