Predictive Value Of Contrast-enhanced MRI For Pathological Complete Response Of Breast Cancer After Neoadjuvant Chemotherapy

Objective: To investigate the accuracy of enhanced MRI(contrast-enhanced MRI)predicting pathologic complete response(pCR)of breast lesions after neoadjuvant chemotherapy(NAC)in patients with early-stage breast cancer,and to accurately screen breast cancer patients who achieve pCR in the breast after NAC.The accuracy of enhanced magnetic resonance assessment of residual breast lesions after NAC was also analyzed to provide a basis for surgical decision making in breast cancer patients after NAC treatment.Methods: Clinical and pathological data were retrospectively collected from245 breast cancer patients who attended the Affiliated Hospital of Southwest Medical University from March 2020 to April 2022 and completed post-NAC surgery.Clinical data included patients’ age at initial consultation,tumor TNM stage at initial consultation,chemotherapy regimen,maximum diameter of pre-NAC breast lesions,maximum diameter of post-NAC breast lesions,and pathological data included maximum diameter of post-NAC breast residual lesions,histological grading,ER expression level,PR expression level,HER-2status,Ki-67 level,and Miller-Payne grading.Four subgroups were divided into HR+/HER2-,HR+/HER2+,HR-/HER2+ and HR-/HER2-according to immunohistochemical results.The value of MRI to evaluate the efficacy of NAC was analyzed using the postoperative pathological findings as the gold standard and compared with the maximum diameter of breast residual tumor assessed by preoperative MRI,with a difference of ≥10 mm between the two assessments,and the four subgroups of HR+/HER2-,HR+/HER2+,HR-/HER2+ and HR-/HER2-were compared.The sensitivity,specificity,and positive predictive value(PPV)of the two thresholds of enhanced MRI for predicting pCR were calculated by assessing NAC as breast rCR and near-rCR with enhanced MRI,respectively,and further analyzing the predictive value of the two assessment criteria for pCR in different subtypes of breast cancer.Kappa values of enhanced MRI prediction thresholds for rCR versus pathology and near-rCR versus pathology findings were calculated for consistency evaluation,respectively.Results: Imaging complete remission(radiological complete response,rCR)was achieved in 88(35.9%)of 245 patients and pathological complete remission(pCR)was achieved in 106(43.3%)patients.Among the overall patients,there was an overestimation of 12.7%(31/245)and an underestimation of 9.8%(24/245)of breast lesion efficacy after NAC assessed using enhanced MRI,respectively.And there were also different degrees of imaging overestimation or underestimation in each subgroup,5.6%(4/72)and 18.1%(13/72)in the HR+/HER2-subgroup,18.1%(13/72)and 6.9%(5/72)in the HR+/HER2+ subgroup,13.0%(6/46)and 2.2% in the HR-/HER2+ subgroup(1/46),and 14.5%(8/55)and 9.1%(5/55)in the HR-/HER2-subgroup.the PPV was 75.0%(66/88)with a MRI prediction threshold of rCR,specificity and sensitivity were 84.2%(117/139)and 62.3%(66/106),respectively,and the Kappa value for whether rCR was associated with whether pCR was The PPV was 67.7%(86/127)with a prediction threshold of near-rCR,specificity and sensitivity were 70.5%(98/139)and 81.1%(86/106),respectively,and the Kappa value for whether rCR was near-rCR versus whether pCR was 0.504.In all subgroups,regardless of whether the MRI prediction threshold was rCR or near-rCR,the HR-/HER2+ subgroup had the highest PPV values,91.7% and83.3%,respectively,while the HR+/HER2-subgroup had the highest Kappa values,0.602 and 0.510,respectively.Conclusion: In the HER2+ breast cancer subgroup,the application of enhanced MRI had a higher risk of overestimation of residual lesions and a lower risk of underestimation.In contrast,for the HR+/HER2-subgroup,enhanced MRI was more likely to underestimate residual lesions and relatively less likely to overestimate residual lesions.Enhanced MRI was more accurate in predicting pCR in the total population,but expanding its predictive forecast did not improve its accuracy in predicting pCR.the HR-/HER2+ subgroup may be a potentially predictable population for pCR-exempt breast surgery,whereas accuracy was lower in the HR+/HER2-subgroup.