Diffusion-Weighted MRI for Selection of Complete Responders After Chemoradiation for Locally Advanced Rectal Cancer: A Multicenter Study

Abstract

PurposeIn 10–24% of patients with rectal cancer who are treated with neoadjuvant chemoradiation, no residual tumor is found after surgery (ypT0). When accurately selected, these complete responders might be considered for less invasive treatments instead of standard surgery. So far, no imaging method has proven reliable. This study was designed to assess the accuracy of diffusion-weighted MRI (DWI) in addition to standard rectal MRI for selection of complete responders after chemoradiation.MethodsA total of 120 patients with locally advanced rectal cancer from three university hospitals underwent chemoradiation followed by a restaging MRI (1.5T), consisting of standard T2W-MRI and DWI (b0-1000). Three independent readers first scored the standard MRI only for the likelihood of a complete response using a 5-point confidence score, after which the DWI images were added and the scoring was repeated. Histology (ypT0 vs. ypT1-4) was the standard reference. Diagnostic performance for selection of complete responders and interobserver agreement were compared for the two readings.ResultsTwenty-five of 120 patients had a complete response (ypT0). Areas under the ROC-curve for the three readers improved from 0.76, 0.68, and 0.58, using only standard MRI, to 0.8, 0.8, and 0.78 after addition of DWI (P = 0.39, 0.02, and 0.002). Sensitivity for selection of complete responders ranged from 0–40% on standard MRI versus 52–64% after addition of DWI. Specificity was equally high (89–98%) for both reading sessions. Interobserver agreement improved from κ 0.2–0.32 on standard MRI to 0.51–0.55 after addition of DWI.ConclusionsAddition of DWI to standard rectal MRI improves the selection of complete responders after chemoradiation.

Can diffusion-weighted MRI determine complete responders after neoadjuvant chemoradiation for locally advanced rectal cancer?

“…In a recent, retrospective, multicenter trial, the added value of DW-MRI in the evaluation of pCR to neoadjuvant CRT was investigated in patients with 120 locally advanced rectal cancer. The sensitivity for the selection of complete responders ranged from 0% to 40% by standard MRI compared to 52%-64% with DW-MRI, and resulted in less overestimation of tumors in patients with a pCR after the addition of DW-MRI (14). In the current study, tumor diffusion SIs were significantly decreased in all patients who had a response after CRT (P < 0.001; Z=4.8).…”

Neoadjuvant therapy for locally advanced rectal cancer

“…Корреляция между МРТ-диагностикой и патомор-фологическим заключением по категории Т равна 64%, а при исследовании лимфатических узлов -65% [18]. При-чины недооценки остаточной опухоли такие же, как и при ультразвуковом исследовании [19]. Тем не менее наиболее информативным методом, особенно в сочетании с иссле-дованием диффузно-взвешенных изображений (ДВИ), является МРТ.…”

Prediction of response to preoperative chemoradiotherapy in patients with locally advanced rectal cancer

“…With the advancement of MRI techniques, recent studies are no longer only reliant on staging rectal cancer patients, but also on prognostic and predictive functions (8,9). Diffusion-weighted MRI (DW-MRI) provides information about microscopic structures through the detection of water proton mobility in biologic tissues (9,11).…”

“…Diffusion-weighted MRI (DW-MRI) provides information about microscopic structures through the detection of water proton mobility in biologic tissues (9,11). In DW-MRI, the apparent diffusion coefficient (ADC) provides a tool for absolute quantitative image analysis.…”