Predictive value of apparent diffusion coefficient for neoadjuvant chemotherapy in locally advanced colorectal cancer patients

BACKGROUND: The efficacy of neoadjuvant chemotherapy is closely related to the long-term prognosis of colorectal cancer (CRC) patients. Apparent diffusion coefficient (ADC) is an index in dynamic enhanced magnetic resonance imaging (MRI), reflecting the density of tumor cells. ADC has been shown to be related to the efficacy of neoadjuvant chemotherapy in other malignant tumors, but there is still a lack of relevant research in CRC patients. METHODS: A total of 128 patients with CRC treated with neoadjuvant chemotherapy in The First Affiliated Hospital of Xiamen University from January 2016 to January 2017 were retrospectively collected. According to the response after neoadjuvant chemotherapy, the patients were divided into an objective response group (n=80) and a control group (n=48). The clinical characteristics and ADC levels of the two groups were compared, and the predictive value of ADC on the efficacy of neoadjuvant chemotherapy was analyzed. The patients were followed up for 5 years to observe the difference of survival rate between the two groups, and further analyzed the correlation between ADC and survival rate. RESULTS: Compared with the control group, the tumor size in the objective response group was significantly reduced (3.32±1.60 vs. 5.07±2.19 cm, P=0.000); ADC significantly increased (1.23±0.18 vs. 0.98±0.18 ×10(−3) mm(2)/s, P=0.000); albumin significantly increased (39.32±4.14 vs. 37.46±4.18 g/L, P=0.016); the proportion of patients with poorly differentiated or undifferentiated tumor cells was significantly lower (51.25% vs. 72.92%, P=0.016); and the 5-year mortality decreased significantly (40.00% vs. 58.33%, P=0.044). ADC had the highest predictive value of objective response for locally advanced CRC patients after neoadjuvant chemotherapy, and the area under the curve (AUC) was 0.834 [95% confidence interval (CI): 0.765–0.903, P=0.000]; ADC had certain predictive value for the 5-year survival of locally advanced CRC patients, and the AUC was 0.778 (95% CI: 0.696–0.861, P=0.000). ADC >1.055×10(−3) mm(2)/s, tumor size <4.1 cm, and moderately or well differentiated tumors were favorable factors for patients with locally advanced CRC to obtain objective response after neoadjuvant chemotherapy (P<0.05). CONCLUSIONS: ADC could be used as a predictor of the efficacy of neoadjuvant chemotherapy in locally advanced CRC patients.