Marcello Alessandro Orsi MD, Presenter: Nothing to Disclose

Francesco Aldo De Cobelli MD, Abstract Co-Author: Nothing to Disclose

Giulia Agostini, Abstract Co-Author: Nothing to Disclose

Maria Alessia Zerella, Abstract Co-Author: Nothing to Disclose

Paolo Passoni, Abstract Co-Author: Nothing to Disclose

Najla Slim, Abstract Co-Author: Nothing to Disclose

Alessandro Del Maschio MD, Abstract Co-Author: Nothing to Disclose

Neoadjuvant CRT is the standard therapeutic option in LARC. TRG is considered a trustable indicator of response and MRI is the reference technique for the evaluation of treatment response in vivo. In this study, we performed pelvic MRI before, during and after CRT to evaluate TVRR at mid-term CRT (mid-TVRR) and after CRT (late-TVRR) in correlation to histological TRG

32 patients affected by LARC, enrolled for preoperative CRT, underwent MRI before, during (at mid-term) and after CRT. On axial T2 images, using a dedicated software, the contour of the tumor was traced, then transformed into a 3-dimensional reconstruction, from which volumetric measurements were calculated. TRG was assessed by histopathology after surgery according to Dworak system (from 0 to 4). Patients with TRG=0-2 were considered as Non Responders (NR) and TRG=3-4 as Responders (R)

Based on histological TRG, 25 patients were classified R and 7 NR. Both Mid-TVRR and Late-TVRR were significantly higher in the R group than in the NR group, respectively 69±15% vs 19±16% (p<0.001; area under the ROC Curve (AUC) 0.98; cut-off value: 48%) and 86±7% vs 44±22% (p=0.002; AUC 0.99; cut-off value: 74%). In the R group, 8/25 were TRG=4 and 17/25 were TRG=3; Mid-TVRR was significantly higher in patients with TRG=4 than TRG=3 (84±7% vs 61±13%; p<0.001; AUC 0.95; cut-off value: 80); no significant difference in Late-TVRR between the two groups was found (89±5% vs 84±8%, p=n.s.)

In our study, TVRR in LARC during CRT presented a strong correlation with histological TRG. Volume reduction, both at half CRT (Mid-TVRR) and after CRT (Late-TVRR) can predict / differentiate R from NR. Moreover, Mid-TVRR was able to predict complete responders (TRG=4) from partial / nearly complete responders (TRG=3)

MRI with volumetric evaluation, performed at half CRT, could early identify patients not responding to CRT, addressing them to alternative or more intense treatment. Moreover, Mid-TVRR, discriminating complete from partial responder patients, could be a powerful tool in addressing complete responders towards a conservative management

Orsi, M, De Cobelli, F, Agostini, G, Zerella, M, Passoni, P, Slim, N, Del Maschio, A, Magnetic Resonance Imaging (MRI) in Locally Advanced Rectal Cancer (LARC): Tumor Volume Reduction Rate (TVRR) Assessed at Mid-term Chemoradiotherapy (CRT) Predicts the Histological Tumor Response Grade (TRG).  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045434.html