Correlation Between Pathologic Complete Response in the Breast and Absence of Axillary Lymph Node Metastases After Neoadjuvant Systemic Therapy.

OBJECTIVE: The aim was to investigate whether pathologic complete response (pCR) in the breast is correlated with absence of axillary lymph node metastases at final pathology (ypN0) in patients treated with neoadjuvant systemic therapy (NST) for different breast cancer subtypes.

BACKGROUND: Pathologic complete response rates have improved on account of more effective systemic treatment regimens. Promising results in feasibility trials with percutaneous image-guided tissue sampling for the identification of breast pCR after NST raise the question whether breast surgery is a redundant procedure. Thereby, the need for axillary surgery should be reconsidered as well.

METHODS: Patients diagnosed with cT1-3N0-1 breast cancer and treated with NST, followed by surgery between 2010 and 2016, were selected from the Netherlands Cancer Registry. Patients were compared according to the pathologic response of the primary tumor with associated pathologic axillary outcome. Multivariable analysis was performed to determine clinicopathological variables correlated with ypN0.

RESULTS: A total of 4084 patients were included for analyses, of whom 986 (24.1%) achieved breast pCR. In clinically node negative patients (cN0), 97.7% (432/442) with breast pCR had ypN0 compared with 71.6% (882/1232) without breast pCR (P < 0.001). In clinically node positive patients (cN1), 45.0% (245/544) with breast pCR had ypN0 compared with 9.4% (176/1866) without breast pCR (P < 0.001). The odds of ypN0 was decreased in case of clinical T3 stage (OR 0.59, 95% CI 0.40-0.87), cN1 (OR 0.03, 95% CI 0.02-0.04) and ER+HER2- subtype (OR 0.30, 95% CI 0.20-0.44), and increased in case of breast pCR (OR 4.53, 95% CI 3.27-6.28).

CONCLUSIONS: Breast pCR achieved after NST is strongly correlated with ypN0 in cN0 patients, especially in ER+HER2+, ER-HER2+, and triple negative subtypes. These results provide data to proceed with future clinical trials to investigate if axillary surgery can be safely omitted in these selected patients when image-guided tissue sampling identifies a breast pCR.