Value Of FMRI For The Diagnosis Of Local Recurrence Of Rectal Cancer

Background and objectiveAround35%of colorectal cancer patients who undergo curative surgical treatment will develop recurrent disease,the majority of which occurring during the first3years after surgery,approximately5-15%of patients will develop a locoregional recurrence.These local recurrences are associated with significant morbidity and impair quality of life. Re-resection of local recurrence can significantly improve the5-year survival of colorectal cancer patients.Therefore it is crucial to monitor after rectal cancer surgery and diagnose local recurrences earlier.As an addition to standard MRI, functional magnetic resonance imaging (fMRI)achieves a comprehensive study of morphology and function.Diffusion weighted imaging(DWI)and dynamic contrast-enhanced MRI(DCE-MRI)could be useful to increase the diagnostic performance for detection of locoregional tumor recurrences.The purpose of this study is to investigate the application of standard MRI,DWI and DCE-MRI for the diagnosis of locoregional tumor recurrence in patients after curative rectal cancer surgery and evaluate the value of DWI and DCE-MRI comparing with standard MRI. Materials and methodsThis study enrolled37patients with a clinical suspieion of recurrence during followup after curative rectal cancer surgery between June2010and Feburary2012. All patients underwent3.0T MRI consisting of standard T2-weighted FSE and axial DWI (b=0,1500) sequence,25patients underwent gadolinium-enhanced LAVA dynamic enhanced sequence. Two readers (R1,R2) independently scored the likelihood of recurrence; on standard MRI and on standard MRI+DWI. Receiver operator characteristic (ROC) curve analyses were performed to evaluate the diagnostic performance for standard MRI only and standard MRI+DWI.Measure the apparent diffusion coefficient (ADC) value of local lesions and analyse the ROC curve of ADC value for diagnosis of tumor recurrence, and calculate the sensitivity and specificity of the cut-off value for diagnosis of recurrence.The dynamic images were reelaborated with semiquantitative postprocessing by plotting intensity-time curves(TIC) and calculating the percentage of signal increase at30s post concrast,analyse the sensitivity and specificity of enhance rate for diagnosis of recurrence.Results16cases were finally diagnosed as local recurrence,21cases were benign change.R1achieved an area under the ROC-curve (AUC) of0.911,sensitivity81.2%and specificity81%on T2WI versus0.957,93.8%and95.2%after addition of DWI (p<0.05). For R2these figures were0.94,87.5%and85.7%on T2WI and0.987,100%and95.2%with DWI (p<0.05). It indieates that the accuracy of standard MRI combined with DWI is significantly higher than that of standard MRI alone.The ADC value of recurrence group was0.90±0.19x10-3mm2/s,the benign group was1.63±0.41×10-3mm2/s,With ADC value of1.33x10-3mm2/s as the cutoff value, the sensitivity,specificity of ADC for the diagnosis of local recurrences was93.7%,95.2%.When setting the cutoff value of enhancement rate to50%, the dynamic enhanced MRI correctly classified9of11recurrences. The enhancement rates of the recurrences ranged from54%to84%, with2false-negative results. It correctly classified11of14benign cases. The enhancement rates of the benign cases ranged from25%to75%, with3false-positive results. the sensitivity, specificity, accuracy, PPV and NPV for the diagnosis of the recurrences is81.8%,78.6%,80%,75%,84.6%.ConclusionMRI is accurate for the diagnosis of locally recurrent rectal cancer in patients with a clinical suspicion of recurrence.Standard MRI combined with DWI can provide better detection for local recurrence than standard MRI alone. The dynamic enhanced MRI has great value in the diagnosis of local recurrence, thus can be considered an important adjunct to standard MRI.