Decrease of peripheral blood lymphocyte count predicts response to neoadjuvant chemotherapy in breast cancer patients.

Purpose: Pathologic complete response (pCR) after neoadjuvant chemotherapy (NAC) holds promise as a significant prognostic factor to predict NAC response in breast cancer patients. The absolute peripheral blood lymphocyte (PBL) count has been suggested as an independent predictor of response to NAC. The current study evaluated the relationship between pCR and the change of PBL count in patients treated with NAC.

Methods: A total of 61 patients with histologically confirmed breast cancer treated with NAC followed by mastectomy between January 2010 and December 2019 were analyzed retrospectively. Correlational analyses confirmed a statistically significant relationship between PBL count and pCR. Following conformational correlational analyses, patients were divided into two groups according to cutoff values using the receiver operating characteristics curve and a logistic regression was conducted to determine the optimal conditions for achieving pCR.

Results: A total of 14 patients (22.9%) achieved pCR. Most PBL counts decreased after NAC relevant to pCR. Logistic regression analysis revealed that a small decrease of PBL was associated with pCR (P=0.028). The cutoff value of PBL decrease was 755×10⁶/L, which was used to divide patients into high and low reduction groups. The pCR rate was 11.43% and 38.46% for the high and low reduction group, respectively (area under the curve, 0.707; 95% confidence interval, 0.556-0.858; P=0.020). The high reduction group was found to have more difficulty achieving pCR.

Conclusion: The decrease of PBL is significantly associated with pCR. Our data support that the decrease of PBL after NAC may be useful factors in predicting the response to NAC in breast cancer patients.