The Use of Apparent Diffusion Coefficient as a Potential Marker of Rectal Cancer Aggressiveness Compared to Contrast Enhanced MRI in Pre Operative Staging of Rectal Carcinoma

Colorectal cancer ranks third amongst the most frequently diagnosed tumors in the world, after lung cancer and breast cancer.Objective: To assess the value of MRI and diffusion MRI in characterization of rectal cancer and to investigate the potential use of the quantified ADC values as imaging biomarker of tumor aggressiveness thus helping in the preoperative staging of rectal carcinoma.Subjects and Methods: 32 patients with rectal cancer were included at this prospective research study at National cancer institute. (19 women, 13 men) from July 2012 to March 2014.Institutional Ethical Committee approval was obtained. All patients gave written consents. All patients were imaged with pelvic MRI examination. A minimum of five pulse sequences (axial T2, T1, and diffusion Wis together with coronal T1 and post contrast dynamic 3D fat sat. T1 Wis gradient study) were performed in all patients. The preoperative radiological staging and post operative pathological results were correlated. Patients with mucinous appearing tumors on the primary staging MRI were excluded.Results: There was a statistically significant correlation between mean ADCs and different tumor T stage. (p= 0.001) with lower ADC values with higher the T stages.Conclusion: The key MR sequence for rectal cancer staging is the T2. The addition of IV gadolinium-enhanced sequence did not improve the diagnostic accuracy for prediction of tumor penetration through the rectal wall. ADC values of rectal cancers significantly correlate with prognostic factors including the MRF status and the T and nodal stages.