The use of a second core needle biopsy to predict response to neoadjuvant chemotherapy in breast cancer patients, especially in the HER2-positive population.

BACKGROUND:Early and accurate assessment of the response to neoadjuvant chemotherapy offers the potential to optimize treatment to obtain improved responses. We aimed to predict the response to neoadjuvant chemotherapy using a second breast core needle biopsy after a median of 2 cycles of neoadjuvant chemotherapy. METHODS:We evaluated 805 consecutive patients undergoing neoadjuvant chemotherapy who had a second core needle biopsy between 2013 and 2017. The second core needle biopsy was performed after a median of 2 cycles of neoadjuvant chemotherapy. Pathologic response was evaluated after completion of all the chemotherapy cycles. Diagnostic values were compared and evaluated between the second core needle biopsy and contrast-enhanced magnetic resonance imaging in both the whole and the human epidermal growth factor receptor 2-positive populations. RESULTS:Overall, 653 patients were eligible and underwent a median of 6 chemotherapy cycles. The second core needle biopsy predicted residual breast cancer earlier than the final contrast-enhanced magnetic resonance imaging, with a greater positive predictive value (positive predictive value: 0.856 vs 0.802, P = .028). Multivariate analysis revealed that a estrogen receptor status, human epidermal growth factor receptor 2 positivity, findings on the final contrast-enhanced magnetic resonance imaging and the pathologic findings of the second core needle biopsy pathology were independent predictive factors for treatment response. The superiority in diagnostic value of a second core needle biopsy pathology in human epidermal growth factor receptor 2-positive patients was consistent with that in the whole population, with a positive predictive value of 0.785 (95% confidence interval: 0.707-0.847). The second core needle biopsy predicted the response to neoadjuvant chemotherapy as early as after 2 cycles, but the accuracy increased from 0.744 to 0.872 if the procedure was performed after more cycles (P = .002). CONCLUSION:The second core needle biopsy predicted the response to neoadjuvant chemotherapy after 2 cycles quite well, especially in human epidermal growth factor receptor 2-positive patients. The ability of the prediction of response improved if the second biopsy was performed after 3 or 4 cycles.