• D Genovesi, A Filippone, G Ausili Cèfaro, M Trignani, A Vinciguerra, A Augurio, M Di Tommaso, V Borzillo, F Sabatino, P Innocenti, E Liberatore, G Colecchia, A Tartaro, and A R Cotroneo.
• Radiation Oncology Department, "G. d'Annunzio" University of Chieti, "SS. Annunziata" Hospital, Chieti, Italy. Electronic address: d.genovesi@unich.it.
• Eur J Surg Oncol. 2013 Oct 1; 39 (10): 1071-8.

PurposeTo evaluate diffusion-weighted imaging (DWI) for assessment of treatment response in locally advanced rectal cancer (LARC) 8 weeks after neoadjuvant chemoradiotherapy (CRT).Methods And MaterialsA total of 28 patients with LARC underwent magnetic resonance imaging (MRI) prior to and 8 weeks after CRT. Tumor volume (TV) was calculated on T2-weighted MRI scans as well as the apparent diffusion coefficient (ADC) was calculated using Echo-planar DWI-sequences. All data were correlated to surgical results and histopathologic tumor regression grade (TRG), according to Mandard's classification. Post-treatment difference ADC (%ΔADC) and TV (%ΔTV) changes at 8 weeks were compared complete response (CR; TRG1) and non-complete response tumors (non-CR; TRG2-5).ResultsThe mean % ADC increase of CR group was significantly higher compared to non-CR group (77.2 ± 54.63% vs. 36.0 ± 29.44%; p = 0.05). Conversely, the mean % TV reduction did not significantly differ in CR group from non-CR group (73.7% vs. 63.77%; p = 0.21). Accordingly, the diagnostic accuracy of the mean % ADC increase to discriminate CR from non-CR group was significantly higher than that of the mean % TV reduction (0.913 vs. 0.658; p = 0.022). No correlation was found between mean % TV reduction and TRG (rho = 0.22; p = 0.3037), whereas a negative correlation between mean % ADC increase and TRG was recorded (r = -0.69; p = 0.006).ConclusionThe mean % ADC increase appears to be a reliable tool to differentiate CR from non-CR after CRT in patients with LARC.Copyright © 2013 Elsevier Ltd. All rights reserved.

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