110P Predictive value of tumor response rate for axillary response of neoadjuvant chemotherapy in patients with clinically nodepositive breast cancer

Abstract

Background Neoadjuvant chemotherapy (NAC) is the standard treatment for patients withclinicallynode-positivebreastcancer. Anaxillarypathologiccompleteresponse (pCR) isassociatedwith excellentprognosis, andpatients whoachieveaxillarypCRcan besparedaxillarylymphnodedissection(ALND). Theaimofthisstudywastoassess the factors thatpredictedaxillarypCR and evaluateda model predicting ofaxillarypCR in our patient population. Methods We retrospectively identified 201 patients with clinically node-positive breast cancer who were treated with NAC and underwent ALND between 2010 and 2015 at Seoul St. Mary's Hospital, Catholic University ofKorea. We analyzed the Baseline patient and tumor characteristics, clinical tumor response rate, pathologic nodal responses.Thetumorresponseratewascalculatedbytherateoftumorandnodalsize reductionbytheResponseEvaluationCriteriainSolidTumorsver.1.1.Theoverall predictionofthemodelincludingtumorresponseratewasassessedbythe discriminative performance by receiver operating characteristic (ROC) curve analysis. Results AxillarypCR was achieved for68 patients (33.8%) who underwentALND after NAC.Patientspresentingwithhighnucleargrade[grade3vs.1 and2,oddsratio(OR) 2.59], higherKi-67 value [>14% vs.(14%, odds ratio (OR) 1.97] andtumorresponse rate [>47.1% vs. < 47.1%, odds ratio (OR) 3.86] were morelikelyto achieve nodalpCR. In multivariate analysis, tumor response rate was the only independent predictor of a pCR (p = 0.0006). The analysis oftumor response ratevalues revealed that 47.1%was a reasonablecutoffvalueforpredictingtheresponsetonodalpCR.Thediscriminationof the model using tumor response rate status versus excluding tumor response rate status [areaunderthecurve(AUC)67.5%,95%CI,0.59-0.76]wassignificantlyimproved using tumorresponseratestatus[areaunderthecurve(AUC) 74.9%,95% CI, 0.68-0.82, P=0.01]. Conclusions Tumor response rate can predict axillary pCR in node-positive patients receiving NAC. This prediction model including tumor response rate shows reasonable accuracy for predicting axillary pCR and may have utility for informing treatment decisions. Legal entity responsible for the study Seoul St. Mary's Hospital Funding Seoul St. Mary's Hospital Disclosure All authors have declared no conflicts ofinterest.