To investigate the predictors of pathological complete response (pCR) after neoadjuvant systemic therapy(NST) in breast cancer patients.

The clinicopathological data of 516 patients with invasive breast cancer who underwent core needle biopsy and surgical resection after NST in the Daping Hospital, Army Medical University from January 1, 2016 to March 1, 2021 were retrospectively analyzed, including patient age, menstrual status, clinical stage, NST regimen and cycle, histological type, histological grade, ER expression, PR expression, HER-2 expression, Ki-67 expression, molecular subtype and postoperative Miller-Payne grades (G1, G2, G3, G4, G5). pCR was defined as G5 with negative regional lymph nodes. The Kruskal-Wallis H test was used to compare the Miller-Payne grades among patients with different clinicopathological characteristics, and χ² test was used to compare the pCR rates. Univariate and forward stepwise logistic regression models were used to analyze independent predictors of pCR.

(1) According to the Miller-Payne grades, there were 123 cases (23.8%) of G4-G5 (pathological remission group), and 393 cases (76.2%) of G1-G3 (non-pathological remission group). Clinical stage, ER expression, PR expression, HER-2 expression, Ki-67 expression, molecular subtypes, NST regimen and NST cycle were all related to the patients’ Miller-Payne grades (χ²=13.572, 19.687, 18.963, 17.989, 15.493, 27.605, 31.622, 10.103, all P<0.050). There were 59 cases (11.4%) of pCR and 457 cases (88.6%) of non-pCR. Menstrual status, histological grade, ER expression, PR expression, HER-2 expression, Ki-67 expression, molecular subtypes, NST regimen, and NST cycle were all related to the patients’ pCR (χ²=3.898, 9.854, 30.593, 17.582, 20.611, 9.303, 33.286, 34.546, 13.846, all P<0.050). (2) The pathological remission rate showed a significant difference among molecular subtypes (χ²=42.117, P<0.001). (3) The logistic regression analysis showed that premenopausal status, clinical stage Ⅲ-Ⅳ, histological grade 3, targeted drugs in NST regimen, HER-2 positive subtype and basal-like subtype were independent predictive factors of increased pCR rate (OR=0.475, 95%CI: 0.256-0.881, P=0.018; OR=0.487, 95%CI: 0.238-0.998, P=0.049; OR=2.108, 95%CI: 1.073-4.141, P=0.030; OR=5.576, 95%CI: 1.958-15.874, P=0.001; OR=10.128, 95%CI: 1.076-95.312, P=0.043; OR=18.497, 95%CI: 2.254-151.815, P=0.007). (4) Clinical stage Ⅲ-Ⅳ, targeted drugs in NST regimen, NST cycles≥5, luminal B (HER-2 negative) subtype, luminal B (HER-2 positive) subtype, HER-2 positive subtype and basal-like subtype were independent predictive factors of increased pathological remission rate (OR=0.436, 95%CI: 0.258-0.738, P=0.002; OR=2.305, 95%CI: 1.109-4.792, P=0.025; OR=2.718, 95%CI: 1.121-6.588, P=0.027; OR=6.764, 95%CI: 1.950-23.463, P=0.003; OR=8.094, 95%CI: 2.048-31.989, P=0.003; OR=12.125, 95%CI: 3.097-47.460, P<0.001; OR=17.182, 95%CI: 4.874-60.577, P<0.001).

The patients with luminal B (HER-2 positive), HER-2 positive and basal-like subtypes (compared with luminal A subtype), early clinical stage, advanced histological grade, ER and PR negative, HER-2 positive, high Ki-67 expression, NST cycles≥ 5 and targeted therapy have higher pCR rates. Menstrual status, clinical stage, histological grade, molecular subtype and NST regimen were independent predictors of pCR.