Diffusion-Weighted MRI as Non-Invasive Diagnostic Tool for Rectal Cancer Aggressiveness and Correlation with KI-67 Expression in Tumor Tissue

BACKGROUND AND AIM: Apparent diffusion coefficient (ADC) was suggested as a prognostic marker in rectal carcinoma (RC). However, reported data are inconsistent. The present study aimed to assess the relation between ADC value and Ki-67 expression index and other pathological parameters in Egyptian RC patients. MATERIALS AND METHODS: The study included 39 patients with newly diagnosed RC (non-mucinous adenocarcinoma). All patients underwent magnetic resonance imaging (MRI) scan by 1.5T magnet. Mean ADC value was calculated. Pathological features were assessed and Ki- 67 immunohistochemical expression was applied as a proliferative index (PI) biomarker. RESULTS: It was shown that patients with T4 tumors had significantly lower ADC values when compared with patients with T2 and T3 (0.903 ± 0.24 versus 1.157 ± 0.31 and 0.971 ± 0.26 respectively, p<0.001). Also, patients with circumferential resection margin (CRM) involvement had significantly lower ADC values when compared with patients without (0.905 ± 0.24 versus 1.109 ± 0.30, p=0.036). Patients with T4 tumors expressed significantly higher ki-67 PI when compared with patients with T2 and T3 tumors (75.71 ± 5.14 versus 46.25 ± 5.18 and 75.71 ± 5.14 respectively, p<0.001). Pearson’s correlation coefficient identified a significant inverse correlation between ADC values and ki-67 PI (r=-367, p=0.027). CONCLUSION: ADC values of RC may reflect tumor staging and Ki-67 is closely related to the ADC value confirm this result.