Diffusion-weighted imaging for evaluating lymph node eradication after neoadjuvant chemoradiation therapy in locally advanced rectal cancer

Background: As lymph node (LN) eradication is the prerequisite for clinical surveillance or local excision for patients who have achieved a complete response after preoperative chemoradiation therapy (CRT), the radiological evaluation of LN eradication is important.

Purpose: To evaluate the added value of diffusion-weighted imaging (DWI) in the evaluation of LN eradication after CRT in patients with locally advanced rectal cancer (LARC).

Material and methods: Ninety-five consecutive patients (64 men, 31 women; mean age, 59 years; range, 32-82 years) who underwent pre- and post-CRT 1.5-T MRI with DWI (b = 0, 1000 s/mm(2)) were enrolled. To evaluate the added value of DWI in the evaluation of LN eradication after CRT, two radiologists first independently read the pre- and post-CRT T2-weighted (T2W) images and then read the combined T2W imaging set and the pre- and post-CRT DWIs with a 4-week interval. The radiologists recorded their confidence scores for LN eradication using a 5-point scale on a per-patient basis. The diagnostic performances were compared between the two reading sessions for each reader with pair-wise comparisons of receiver-operating characteristic curves. Histopathological reports served as the reference standards for LN eradication.

Results: The study population consisted of an LN-eradicated group (n = 66) and a non-eradicated group (n = 29). The diagnostic performances did not significantly differ between the two reading sessions for the two readers (AUCs for reader 1, 0.770 and 0.774, P = 0.8155; for reader 2, 0.794 and 0.798, P = 0.8588).

Conclusion: Adding DWI to T2W imaging provided no additional diagnostic benefit for the evaluation of LN eradication following CRT in patients with LARC.