Objective To investigate the value of ultrasound-guided diffuse optical tomography（US-DOT） in predicting the efficacy of neoadjuvant chemotherapy（NCT） for breast cancer.Methods Fifty-eight cases of breast cancer treated with NCT were enrolled.US-DOT was performed to obtain tumor size and hemoglobin concentration（HBT） at pre-first and post-last chemotherapy.According to the Response Evaluation Criteria in Solid Tumor standard

the lesions were divided into complete response group（n=8）

partial response group（n=33） and stable disease group（n=17）.The changes of HBT and tumor size before and after NCT in each group were analyzed.The relationship between HBT changes（△HBT%） and tumor size changes（△Size%） was analyzed by Pearson correlation.Receiver operating characteristic（ROC） curve was established to predict the optimal threshold of △ HBT% and its diagnostic efficacy for breast cancer neoadjuvant chemotherapy.Results The HBT and tumor size of the lesions after NCT were lower than those before NCT

and the differences were statistically significant（all P<0.001）.After NCT

the differences of △HBT% and △Size% were statistically significant among the groups（all P<0.001）.Pearson correlation analysis showed that △ HBT% was positively correlated with △Size%（r=0.874

P<0.001）.Taking △HBT%was 22.9% as the optimal threshold to predict NCT efficacy

the area under the ROC curve was 0.872

and the sensitivity was 82.93%

specificity was 76.47%

positive predictive value was 89.47%

negative predictive value was 65.00%

and accuracy was 81.03%

respectively.Conclusion US-DOT can predict the efficacy of NCT for breast cancer by monitoring △HBT% and has higher value in clinical application.