Local staging of sigmoid colon cancer using MRI

An accurate radiological staging of colon cancer is crucial to select patients who may benefit from neoadjuvant chemotherapy.

To evaluate the diagnostic accuracy of preoperative magnetic resonance imaging (MRI) in identifying locally advanced sigmoid colon cancer, poor prognostic factors, and the inter-observer variation of the tumor apparent diffusion coefficient (ADC) values of diffusion-weighted imaging (DWI).

Using 1.5 T MRI with high resolution T2-weighted (T2W) imaging, DWI, and no contrast enhancement, 35 patients with sigmoid colon cancer were assessed. T-stage, N-stage, extramural vascular invasion (EMVI), and ADC values of the tumors were assessed and blindly compared by two observers using postoperative histopathological examination as the gold standard. Early tumors were defined as T1 to T3ab, and advanced tumors as T3cd or T4.

The accuracy of the two radiologists in staging early versus advanced tumors, N-stage, and identification of EMVI was 94%/89%, 60%/66%, and 77%/60% with an inter-observer agreement of к = 0.86 (95% confidence interval [CI] = 0.67-1.00), к = 0.64 (95% CI = 0.39-0.90), and к = 0.52 (95% CI = 0.23-0.80). All the measured mean ADC values were below 1.0 × 10^-3 mm²/s with an intra-class correlation coefficient in T3cd-T4 tumors of 0.85.

Preoperative MRI can identify locally advanced sigmoid colon cancer and has potential as the imaging of choice to select patients for neoadjuvant chemotherapy. Initial experience with ADC measurement was achieved with an excellent inter-observer agreement in advanced tumors.