Value of diffusion-weighted MRI and apparent diffusion coefficient measurements for predicting the response of locally advanced rectal cancer to neoadjuvant chemoradiotherapy.
The aim of our study was to assess the performance value of magnetic resonance imaging (MRI) in the restaging of locally advanced rectal cancer after neoadjuvant chemoradiotherapy (CRT) and in the identification of good vs. poor responders to neoadjuvant therapy.



A total of 34 patients with locally advanced rectal cancer underwent MRI prior to and after CRT. T stage and tumor regression grade (TRG) on post-CRT MRI was compared with the pathological staging ypT and TRG. Tumor volume and the apparent diffusion coefficient (ADC) were measured using diffusion-weighted imaging (DWI) before and after neoadjuvant CRT; the percentage of tumor volume reduction and the change of ADC (ΔADC) was also calculated. ADC parameters and the percentage of tumor volume reduction were correlated to histopathological results. The diagnostic performance of ADC and volume reduction to assess tumor response was evaluated by calculating the area under the ROC curve and the optimal cut-off values.



A significant correlation between the T stage and the TRG defined in DW-MRI after CRT and the ypT and the TRG observed on the surgical specimens was found (p = 0.001; p < 0.001). The mean post-CRT ADC and ΔADC in responder patients was significantly higher compared to non-responder ones (p = 0.001; p = 0.01). Furthermore, the mean post-CRT ADC values were significantly higher in tumors with T-downstage (p = 0.01).



DW-MRI may have a significant role in the restaging and in the evaluation of post-CRT response of locally advanced rectal cancer. Quantitative analysis of DWI through ADC map may result in a promising noninvasive tool to evaluate the response to therapy.
Radiology Department, Faculty of Medicine and Psychology, Sapienza University of Rome, Sant'Andrea Hospital, Via di Grottarossa, 1035, 00189, Rome, Italy.
Elsa
E
Iannicelli
Radiology Department, Faculty of Medicine and Psychology, Sapienza University of Rome, Sant'Andrea Hospital, Via di Grottarossa, 1035, 00189, Rome, Italy. Marco.dipietropaolo@uniroma1.it.
Marco
M
Di Pietropaolo
Department of Clinical and Molecular Sciences, Faculty of Medicine and Psychology, Sapienza University of Rome, Sant'Andrea Hospital, Via di Grottarossa 1035, 00189, Rome, Italy.
Emanuela
E
Pilozzi
Radiation Oncology, Faculty of Medicine and Psychology, Sapienza University of Rome, Sant'Andrea Hospital, Via di Grottarossa 1035, 00189, Rome, Italy.
Mattia Falchetto
MF
Osti
Radiotherapy Unit, San Pietro Fatebenefratelli Hospital, Via Cassia 600, 00189, Rome, Italy.
Maria
M
Valentino
Department of Surgery, Faculty of Medicine and Psychology, Sapienza University of Rome, Sant'Andrea Hospital, Via di Grottarossa 1035, 00189, Rome, Italy.
Luigi
L
Masoni
Department of Surgery, Faculty of Medicine and Psychology, Sapienza University of Rome, Sant'Andrea Hospital, Via di Grottarossa 1035, 00189, Rome, Italy.
Mario
M
Ferri
D000368:Aged; D059248:Chemoradiotherapy; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D011237:Predictive Value of Tests; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy*; D016896:Treatment Outcome
Apparent diffusion coefficient; Chemoradiotherapy; Diffusion-weighted imaging; Locally advanced rectal cancer; Magnetic resonance imaging; TRG