Dual-energy CT can detect malignant lymph nodes in rectal cancer

There is a need for an accurate and operator independent method to assess the lymph node status to provide the most optimal personalized treatment for rectal cancer patients. This study evaluates whether Dual Energy Computed Tomography (DECT) could contribute to the preoperative lymph node assessment, and compared it to Magnetic Resonance Imaging (MRI). The objective of this prospective observational feasibility study was to determine the clinical value of the DECT for the detection of metastases in the pelvic lymph nodes of rectal cancer patients and compare the findings to MRI and histopathology.

The patients were referred to total mesorectal excision (TME) without any neoadjuvant oncological treatment. After surgery the rectum specimen was scanned, and lymph nodes were matched to the pathology report. Fifty-four histology proven rectal cancer patients received a pelvic DECT scan and a standard MRI. The Dual Energy CT quantitative parameters were analyzed: Water and Iodine concentration, Dual-Energy Ratio, Dual Energy Index, and Effective Z value, for the benign and malignant lymph node differentiation.

DECT scanning showed statistical difference between malignant and benign lymph nodes in the measurements of iodine concentration, Dual-Energy Ratio, Dual Energy Index, and Effective Z value. Dual energy CT classified 42% of the cases correctly according to N-stage compared to 40% for MRI.

This study showed statistical difference in several quantitative parameters between benign and malignant lymph nodes. There were no difference in the accuracy of lymph node staging between DECT and MRI.