Preoperative evaluation of colorectal cancer using CT colonography, MRI, and PET/CT

Abstract

Imaging studies are a major component in the evaluation of patients for the screening, staging and surveillance of colorectal cancer. This review presents commonly encountered findings in the diagnosis and staging of patients with colorectal cancer using computed tomography (CT) colonography, magnetic resonance imaging (MRI), and positron emission tomography (PET)/CT colonography. CT colonography provides important information for the preoperative assessment of T staging. Wall deformities are associated with muscular or subserosal invasion. Lymph node metastases from colorectal cancer often present with calcifications. CT is superior to detect calcified metastases. Three-dimensional CT to image the vascular anatomy facilitates laparoscopic surgery. T staging of rectal cancer by MRI is an established modality because MRI can diagnose rectal wall laminar structure. N staging in patients with colorectal cancer is still challenging using any imaging modality. MRI is more accurate than CT for the evaluation of liver metastases. PET/CT colonography is valuable in the evaluation of extra-colonic and hepatic disease. PET/CT colonography is useful for obstructing colorectal cancers that cannot be traversed colonoscopically. PET/CT colonography is able to localize synchronous colon cancers proximal to the obstruction precisely. However, there is no definite evidence to support the routine clinical use of PET/CT colonography.

Evaluation of EphA2 and EphB4 as Targets for Image-Guided Colorectal Cancer Surgery

“…A recent study also developed NIR fluorescence probes for EphB4 targeted imaging using an EphB4 antibody [27]. While the use of PET for colon cancer is not suitable for routine clinical use [28], NIR fluorescence-based imaging of colorectal cancer shows great potential for clinical use, especially for rectal cancer [29]. In conclusion, both EphA2 and EphB4 show potential as target for image-guided colorectal cancer surgery, but EphB4 seems to have the best characteristics.…”

PET/MRI: Where might it replace PET/CT?

“…Determining N‐stage is more difficult using anatomic imaging alone, because metastatic lymph nodes may be no larger than those not affected by disease . Therefore, there is a role for PET because typically the standardized uptake values (SUV) of metastatic nodes are greater than those not involved . Finally, the added benefits of PET/MRI with simultaneously obtained and co‐registered data for evaluation of the liver in a single examination, potentially using hepatobiliary contrast agents would allow for complete detection and characterization of hepatic metastases which, if present, would affect M‐stage …”

“…79 Therefore, there is a role for PET because typically the standardized uptake values (SUV) of metastatic nodes are greater than those not involved. 80 Finally, the added benefits of PET/MRI with simultaneously obtained and co-registered data for evaluation of the liver in a single examination, potentially using hepatobiliary contrast agents would allow for complete detection and characterization of hepatic metastases which, if present, would affect M-stage. 65 While clinical staging of cervical cancer has been the long-term accepted solution for local disease, 81 PET/CT has a role in the detection of distant metastases, 82 and there is evolving understanding that pelvic MRI may offer benefit in the preoperative evaluation of tumor stage.…”

Diagnostic and prognostic value of preoperative 18F-fluorodeoxyglucose positron emission tomography/computed tomography for colorectal cancer: comparison with conventional computed tomography

“…Therefore, small lymph node metastasis can be hard to detect with FDG-PET/CT, resulting in low sensitivity of the examination. However, if the SUVmax is 2 or 3, pathological metastatic lymph nodes can frequently be seen 26. In addition, FDG-PET/CT with high specificity can help to clarify the nature of uncertain lymph nodes detected by other imaging modalities such as CT.…”