ObjectiveTo analyze the factors influencing axillary pathological complete response (pCR) after neoadjuvant therapy (NAT) and to provide the possibility of exempting axillary surgery for patients with better pathological efficacy of primary breast lesions after NAT. MethodsAccording to the inclusion and exclusion criteria, the patients with breast cancer admitted to the Department of Breast Surgery, Affiliated Hospital of Southwest Medical University from January 1, 2020 to June 30, 2022 were retrospectively analyzed. All patients were diagnosed with ipsilateral axillary lymph node metastasis of breast cancer and the NAT cycle was completed according to standards. All patients underwent axillary lymph node dissection (ALND) after NAT. The therapeutic effect of primary breast lesions was evaluated by Miller-Payne (MP) grading system. The axillary pCR was judged according to whether there was residual positive axillary lymph nodes after ALND. The unvariate and multivariate logistic regressions were used to analyze the risk factors affecting the axillary pCR. At the same time, the possibility of exempting axillary surgery after NAT in the MP grade 5 or in whom without ductal carcinoma in situ (DCIS) was evaluated. The ALND was considered to exempt when the negative predictive value was 90% or more and false negative <10% or almost same. ResultsA total of 111 eligible patients with breast cancer were gathered in the study, 64 of whom with axillary pCR. There were 43 patients of MP grade 5 without DCIS after NAT, 41 of whom were axillary pCR. The univariate analysis results showed that the estrogen receptor and progesterone receptor statuses, molecular type, NAT regimen, and MP grade were associated with the axillary pCR after NAT, then the logistic regression multivariate analysis results showed that the MP grade ≤3 and MP grade 4 decreased the probability of axillary pCR as compared with the MP grade 5 [OR=0.105, 95%CI (0.028, 0.391), P=0.001; OR=0.045, 95%CI (0.012, 0.172), P<0.001]. There were 51 patients of MP grade 5 after NAT, 46 of whom were axillary pCR. The negative predictive value and the false negative rate of MP grade 5 on predicting the postoperative residual axillary lymph nodes were 90.2% [95%CI (81.7%, 98.6%)] and 10.6% [95%CI (1.5%, 19.8%)], respectively, which of MP grade 5 without DCIS were 95.3% [95%CI (88.8%, 101.9%)] and 4.3% [95%CI (–1.7%, 10.2%)] , respectively. ConclusionsThe probability of axillary pCR for the patient with higher MP grade of breast primary after NAT is higher. It is probable of exempting axillary surgery when MP grade is 5 after NAT.