MRI surveillance for the detection of local recurrence in rectal cancer after transanal endoscopic microsurgery

Objectives To evaluate diagnostic performance of follow-up MRI for detection of local recurrence of rectal cancer after transanal endoscopic microsurgery (TEM). Methods Between January 2006 and February 2014, 81 patients who underwent TEM were included. Two expert readers (R1 and R2), independently evaluated T2-weighted (T2W) MRI and diffusion-weighted (DWI) MRI for the detection of local recurrence, retrospectively, and recorded confidence on a five-point scale. Diagnostic performance of follow-up MRI was assessed using ROC-curve analysis and kappa statistics for the reproducibility between readers. Results 293 MRIs were performed, 203 included DWI. 18 (22%) patients developed a local recurrence: luminal 11, nodal two and both five. Areas under the curve (AUCs) for local recurrence detection were 0.72 (R1) and 0.80 (R2) for T2W-MRI. For DWI, AUCs were 0.70 (R1) and 0.89 (R2). For nodal recurrence AUCs were 0.72 (R1) and 0.80 (R2) for T2W-MRI. Reproducibility was good for T2W-MRI (κ0.68 for luminal and κ0.71 for nodal recurrence) and moderate for DWI (κ0.57). AUCs and reproducibility for recurrence detection increased during follow-up. Conclusions Follow-up with MRI after TEM for rectal cancer is feasible. Postoperative changes can be confusing at the first postoperative MRI, but during follow-up diagnostic performance and reproducibility increase. Key Points • Follow-up with MRI is feasible for follow-up after TEM for rectal cancer. • DWI-MRI is a useful addition to detect recurrences after TEM. • Postoperative changes can be confusing and can lead to underestimation of recurrence. • Appearance of intermediate signal at T2W-MRI is suspicious for recurrence. • Nodal staging remains challenging.