Abstract: Abstract:Objective To explore and evaluate the clinical value of MRI for status of axillary lymph node after neoadju⁃ vant chemotherapy (NAC) in patients with breast cancer. Methods Forty-four patients with 1ocally advanced breast cancer (LABC) were underwent NAC for four cycles. The longest diameter of axillary lymph node (ALN) measured by MRI scan. Val⁃ ue of apparent diffusion coefficient (ADC) and their correlation were compared before NAC and four cycles after NAC. Re⁃ sults of MRI and pathological data for ALN were compared between two groups of patients. Results All patients finished four cycles of NAC. The total response rate (CR+PR) was 72.7% (32/44), and the total non-response rate (SD+PD) was 27.3% (12/44). The longest diameter of ALN was significantly shortened in response group. The longest diameter was (1.37± 1.06) cm before NAC and (0.90±0.76) cm after NAC (P＜0.01). The ADC value of the tumor was significantly increased in re⁃ sponse group [(0.91±0.28) ×10-3 mm2 /s before NAC and (1.01±0.32)×10-3 mm2 /s after NAC, P＜0.01)]. There was no signifi⁃ cant correlation between ADC value change (△ADC) and the longest diameter change of ALN (△L, r=0.131, P=0.413). The sensitivity, specificity and Kappa value of ALN evaluation after NAC were 100%, 62.5% and 0.68 measured by MRI. Con⁃ clusion The change of tumor longest diameter reflects the effect of chemotherapy directly. The tumor ADC value of MRI can not be used as an independent indicator of chemotherapy effect of ALN, eventhouth MRI was the sensitive index for eval⁃ uating the status of axillary lymph node after neoadjuvant chemotherapy for breast cancer.

Key words: breast neoplasms, chemotherapy, adjuvant, magnetic resonance imaging, signal processing, computer-as? sisted, lymphatic metastasis, treatment outcome, neoadjuvant chemotherapy, apparent diffusion coefficient