Based on Histogram Analysis: ADC Derived from Ultra-high B-Value DWI Could Be a Non-invasive Specific Biomarker for Rectal Cancer Prognosis

Aquaporins (AQP) are not only water channel protein, but also potential prognostic indicator and therapeutic target for rectal cancer. Some previous studies have demonstrated the AQP expression could be estimated by ADC value derived from ultra-high b-value diffusion-weighted imaging (DWI). We aim to determine whether ADC could be a new and specific biomarker for indicating the AQP expression and prognostic factors of rectal cancer. 76 untreated patients with rectal cancer confirmed by colonoscopy biopsy were enrolled. ADC value was generated from ultra-high b-value DWI with five b-values (1700-3500 s/mm). AQP (AQP1, 3 and 5)staining intensity was estimated by both of software (QuPath) and manual manner. The relationships between histogram features of ADC and AQP staining intensity were analyzed. The correlations between histogram features of ADC and differentiation degrees (good, moderate, poor), T stage (T1-2 vs T3-4), and lymph node status (N+ vs N-) were also evaluated respectively. The mean, 75 percentile and 97.5 percentile of ADC were correlated with AQP1 staining intensity (r = 0.237, 0.323 and 0.362, respectively, all P < 0.05) . No correlation was found between the histogram features of ADC and AQP3 or AQP5 staining intensity. The mean, 50 percentile, 75 percentile and 97.5 percentile of ADC value exhibited significant differences between differentiation status (all P < 0.05). Histogram features of ADC value showed no significant differences in two subgroups of T stage and lymph node status (all P > 0.05). Histogram analysis showed that the ADC value derived from ultra-high b-value DWI of rectal cancer could reflect AQP1's expression and rectal cancer's malignancy degree. ADC might be a new imaging biomarker for evaluating rectal cancer.