ECR 2013 Rec: Additional value of diffusion-weighted (DWI) MRI for predicting complete tumour response (T0N0) in rectal cancer treated with neo-adjuvant chemoradiation therapy (CRT) #B0627 #SS1316

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B-0627 Additional value of diffusion-weighted (DWI) MRI for predicting complete tumour response (T0N0) in rectal cancer treated with neo-adjuvant chemoradiation therapy (CRT)

S. Sassen, M. de Booij, M.N. Sosef, G. Lammering, C.M.M. Bakker, R. Clarijs, R.C.M. Berendsen, J. Wals, R.F.A. Vliegen | Sunday, March 10, 10:30 – 12:00 / Room A

Purpose: Patients with complete response (CR) after CRT might be considered for less aggressive treatment like a wait-and-see strategy. Few studies investigated the value of DWI-MRI for predicting CR after CRT, but none included lymph nodes in the analysis (ypT0N0). The aim of the present study was to retrospectively determine the additional value of DWI-MRI to conventional (T2-weighted) MRI for predicting CR after CRT.
Methods and Materials: Eighty locally advanced rectal cancer patients underwent CRT followed by restaging MRI and operation. MRI consisted of conventional sequences and DWI. Two readers with different levels of experience independently scored conventional images for CR and, in a second reading, combined conventional and DWI-MRI images. A 5-point confidence level score was used to generate ROC curves. Differences in performance were calculated by comparing areas under the ROC curves (AUC). Interobserver agreement, sensitivity, specificity and positive predictive values (PPV) were calculated. Histology served as reference standard.
Results: Ten of 80 patients (13%) had a pathologic complete response (ypT0N0). Comparison of the ROC curves showed significant improvement of the AUC only for the experienced reader 1 from 0,77 to 0,88 (p=0,009). Sensitivity improved from 20-30% to 40-70%. Specificity and PPV improved only for reader 1 from 87 to 93 %, resp., 25 to 58 %. Interobserver agreement improved from 0,14 to 0,27.
Conclusion: Adding DWI to conventional MRI improves diagnostic performance of experienced readers and increases interobserver agreement for identification of CR. Sensitivity and PPV remain low, with a considerable risk of over- and undertreatment.

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14
Sep 2013
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