Abstract
Background: It is challenging to restage rectal cancer at MRI, in patients who have had neoadjuvant chemoradiotherapy.Objective: To investigate the accuracy of MRI with diffusion-weighted imaging (DWI) in the restaging of rectal cancer.Materials and methods: Pre- and post-neoadjuvant chemoradiotherapy MRI examinations of 35 patients diagnosed with locally advanced rectal cancer were evaluated and subsequently compared with post-operative pathology results.Results: The accuracy of MRI with DWI to determine the T-stage status was calculated as 54.28%. Kappa statistics revealed poor concordance with pathology results, with a κ value of 0.212 ± 0.114 (p = 0.028). The apparent diffusion coefficient (ADC) values measured after the neoadjuvant chemotherapy revealed a significant increase when compared with pre-treatment ADC values (p < 0.000001). MRI accuracy rate for lymph node involvement was calculated as 57.14% with a κ value of 0.001 (p = 0.989). MRI had 80% sensitivity and 100% specificity in determining mesorectal fascia involvement, with a calculated positive predictive value of 100% and a calculated negative predictive value of 96%. The accuracy of MRI in overall staging according to the TNM staging system was 28%.Conclusion: The accuracy of MRI in restaging rectal cancer is not yet sufficient and is not on par with the accuracy of MRI in the primary staging of the disease. This is attributed to post-treatment changes. Adding DWI to the protocol is promising, but more expanded data are required.
Highlights
Magnetic resonance imaging (MRI) has been shown to be a useful tool in staging rectal cancer preoperatively.[1,2,3,4,5] It has been reported to be highly accurate in the detection of circumferential resection margin (CRM) involvement and defining the T-stage of the tumour, but assessment of lymph node involvement is not as successful
Diffusion-weighted MRI is a functional MRI technique that is based on differences in the extracellular movement of water protons which is determined by the cellularity of the structures
diffusion-weighted imaging (DWI) has been shown as a promising tool for the identification of malignant tumours, and recent studies on rectal cancer have indicated that DWI may be useful for response evaluation after chemoradiation treatment
Summary
Magnetic resonance imaging (MRI) has been shown to be a useful tool in staging rectal cancer preoperatively.[1,2,3,4,5] It has been reported to be highly accurate in the detection of circumferential resection margin (CRM) involvement and defining the T-stage of the tumour, but assessment of lymph node involvement is not as successful. Diffusion-weighted MRI is a functional MRI technique that is based on differences in the extracellular movement of water protons which is determined by the cellularity of the structures. In tissues with normal cellularity, water protons diffuse freely, and they are appreciated as low signal structures on diffusion-weighted imaging (DWI). It is challenging to restage rectal cancer at MRI, in patients who have had neoadjuvant chemoradiotherapy
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