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

Abstract 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.