Monique Maas MD, Presenter: Nothing to Disclose

Doenja Marina Johanna Lambregts MD, PhD, Abstract Co-Author: Nothing to Disclose

Luc Heijnen, Abstract Co-Author: Nothing to Disclose

Milou Martens, Abstract Co-Author: Nothing to Disclose

Jeroen Leijtens, Abstract Co-Author: Nothing to Disclose

Meindert Sosef, Abstract Co-Author: Nothing to Disclose

Karel Hulsewe, Abstract Co-Author: Nothing to Disclose

Geerard L. Beets MD, PhD, Abstract Co-Author: Nothing to Disclose

Regina G. H. Beets-Tan MD, PhD, Abstract Co-Author: Nothing to Disclose

Chemoradiation (CRT) for rectal cancer leads to complete tumour response (CR) in 15-25% of the cases. Accurate identification of a CR is necessary to allow for less invasive treatments (e.g. local excision or wait&see). Standard imaging cannot accurately identify a CR due to incorrect overestimation of fibrosis as residual tumour. Aim was to evaluate what is the best strategy to identify patients with a CR by use of T2W MRI, DWI and endoscopy.

49 patients underwent CRT and restaging consisting of T2W-MRI, DWI and endoscopy 8 weeks after completion of CRT. One reader scored the T2W images followed by immediate evaluation of the DWI images with the T2W images at his disposal. A second reader scored the endoscopy images. Readers were blinded for histology and each others’ results. Scoring was performed with a confidence level score (0=definitely residual tumour, 4=definitely CR).

Of the 49 patients, 18 had residual tumour and 31 had a CR. The AUCs for T2W-MRI, T2+DWI and endoscopy were 0.71, 0.78 and 0.88, respectively. Corresponding sensitivities and specificities were 39%&87% for T2W, 39%&93% for T2+DWI and 67%&97% for endoscopy. When a combination of MRI (T2W and DWI) with endoscopy was used the highest accuracy was reached: 0.91.

The combination of endoscopy, T2W-MRI and DWI leads to a very high accuracy for the identification of patients with a CR after CRT for rectal cancer. Endoscopy corrects for overestimation of fibrosis as residual tumour with MRI. MRI provides a low risk for missing residual tumour and thus guarantees a safe selection process. It is therefore highly recommendable to use this combination of endoscopy and T2W-MRI with DWI to select patients with a CR after CRT, particularly now less invasive treatment is increasingly being considered as an alternative for standard TME.

Use of endoscopy with T2WMRI+DWI for the selection of a CR after CRT for rectal cancer leads to a high accuracy and is recommended for restaging when considering less invasive treatment instead of TME.

Maas, M, Lambregts, D, Heijnen, L, Martens, M, Leijtens, J, Sosef, M, Hulsewe, K, Beets, G, Beets-Tan, R, Most Accurate Selection of Complete Responders After Chemoradiation for Rectal Cancer with a Combination of T2-weighted MRI, Diffusion-weighted MRI and Endoscopy.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13023310.html