ObjectiveTo investigate the clinical value of magnetic resonance imaging (MRI) combined with ultrasound (US) contrasting with MRI in evaluating the pathological complete response (pCR) of breast cancer after neoadjuvant chemotherapy (NAC).MethodsThe imaging data of patients with primary invasive breast cancer who completed the surgical resection after NAC and met the inclusion criteria in the Breast Disease Diagnosis and Treatment Center of Affiliated Hospital of Qingdao University from December 2016 to December 2019 were collected retrospectively. These patients were evaluated by MRI and MRI combined with US examination respectively. The results of MRI alone and MRI combined with US were designed into imaging of complete remission (rCR) and imaging of non-complete remission (non-rCR). With results of postoperative pathology as the gold standard, the sensitivity, specificity, and positive predictive value (PPV) of MRI alone and MRI combined with US in predicting pCR of patients with rCR or non-rCR were calculated and which were further analyzed in the 4 subtypes of breast cancer (HR+/HER2+, HR+/HER2–, HR–/HER2+, and HR–/HER2– subtype).Results① According to the inclusion and exclusion criteria, a total of 146 patients with primary invasive breast cancer were included, including 34 cases of HR+/HER2+subtype, 63 cases of HR+/HER2– subtype, 23 cases of HR–/HER2+ subtype, and 26 cases of HR–/HER2– subtype. ② After NAC, 36 cases had a pCR, among which 9 cases (26.5%) were in HR+/HER2+ subtype, 10 cases (15.9%) were in HR+/HER2– subtype, 8 cases (34.8%) were in HR–/HER2+ subtype, and 9 cases (34.6%) were in HR–/HER2– subtype. ③ After NAC, 22 (78.6%) of the 28 patients evaluated by MRI alone achieved pCR, 17 (81.0%) of the 21 patients evaluated by MRI combined with US achieved pCR, and the PPV value of pCR evaluated by MRI alone and MRI combined with US was 78.6% and 81.0%, respectively. ④ Both MRI alone and MRI combined with US predicted NAC showed the highest PPV values in patients with HR–/HER2– subtype breast cancer (85.7% and 100%, respectively), and the lowest values in HR+/ HER2– subtype breast cancer (71.4% and 60.0%, respectively).ConclusionFor the overall patients with primary invasive breast cancer, MRI combined with US is superior to MRI alone in the evaluation of efficacy after NAC, and among the patients with different subtypes of breast cancer, except HR+/HER2– subtype, MRI combined with US is still more effective in predicting efficacy after NAC than MRI alone.