Value of magnetic resonance and diffusion-weighted imaging for diagnosis and assessment of rectal cancer

Early diagnosis of rectal cancer is essential to improve patient survival, as advanced-stage patients have limited therapeutic options and poor prognosis. Imaging modalities, particularly magnetic resonance imaging (MRI), are important clinical tools for diagnosis and assessment of rectal cancer. This study analyzed the value of MRI conventional sequences and diffusion-weighted MRI (DWI) for diagnosis and assessment of rectal cancer. This study included 80 subjects: a case group of 40 subjects with rectal cancer, and a control group of 40 subjects with benign rectal tumors. MRI and DWI scans were used to detect apparent diffusion coefficients (ADC) of tumor tissue and normal tissue of the intestinal wall. Results were analyzed and compared with postoperative pathology staging and types. The area under the receiver-operating-characteristic curve (AUC) of MRI and DWI scans for diagnosis of rectal cancer were 0.921 and 0.992, respectively. ADC of rectal tumor tissue was significantly lower than that of normal rectal tissue (t = 14.544; P<0.05), and AUC of ADC values for rectal cancer was 0.995. Compared with postoperative pathology examination, Kappa values of pathology staging of rectal cancer assessed through MRI and DWI were 0.552 and 0.772, respectively. In addition, ADC values were significantly different among different rectal cancer pathologies (F = 15.346; P<0.05). ADC of highly differentiated adenocarcinoma was significantly higher than that of moderately differentiated adenocarcinoma or poorly differentiated adenocarcinoma. AUC of ADC values for poorly differentiated rectal adenocarcinoma was 0.744. In brief, DWI has higher value in diagnosis and assessment of rectal cancer than MRI conventional sequences. Quantitative measurement of ADC values can aid diagnosis of rectal cancer pathologies and can be used in preoperative assessments of degree of progression and malignancy of rectal cancer.