Positron Emission Tomography/Computerized Tomography Functional Imaging of Esophageal and Colorectal Cancer

Abstract

Positron Emission Tomography/Computerized Emission Tomography (PET/CT) creates fusion images which are a combination of tissue function (PET) and anatomy (CT). PET/CT imaging for esophageal and colorectal cancers improves staging, detection of recurrence, and treatment monitoring. Both tumor types are highly metabolically active in the untreated state, and the glucose analog, 2-[18F]-2-fluoro-2-deoxy-D-glcuose, (FDG), is widely useful as a PET imaging tracer for these malignancies. For esophageal and colorectal malignancies, diagnostic imaging sensitivity and specificity are greater than 90%. For esophageal tumors, PET imaging is standard of care for staging of locally advanced tumor. Fifteen to 20% of patients will have other wise occult metastatic sites detected by PET imaging at initial staging. Progression free survival and survival are correlated with the magnitude of reduction in PET-FDG measured metabolic activity post-treatment. For colorectal cancers, PET-FDG is standard of care to detect recurrence, and to monitor treatment response. The addition of CT to the PET imaging, causes a significant reduction in uncertainty of image interpretation and improves the distinction between benign and malignant causes for FDG-PET positive sites.

Surgical Therapy for Colorectal Metastases to the Liver

“…[77][78][79] More recently, PET has been combined with CT (PET/CT) in the same gantry, providing the advantage of anatomic localization of the PET scan abnormalities. [80][81][82][83][84] Yeung et al 85 has reported that combined PET/CT results in increased reader confidence and 53% fewer equivocal readings on the part of the radiologist, as well as an improved positive predictive value compared with PET alone. Currently, there is a general consensus that PET/CT is the most accurate method for staging advanced colorectal cancer, particularly when metastasectomy is being considered and when the patient has possible locoregional recurrent disease.…”

Computed tomography volumetry of esophageal cancer - the role of semiautomatic assessment

“…Other methods than CT can add to the armamentarium of methods allowing tumor volume detection and assessment of changes therein. PET-CT imaging with 18 FDG has recently been shown to offer advantages in monitoring the response to neoadjuvant treatment of esophageal cancer by measuring the metabolic/volume activity [21, 30, 31]. However, uncertainties regarding which thresholds of standardized uptake value (SUV) during the delineation of tumor remain as a source of variability in previous studies and there is currently no standardized protocol in use.…”

Diagnostic radiology and nuclear medicine

“…A solution to the limited spatial resolution of PET comes with its hybridization with CT in a single unit, which allows precise image fusion of the anatomic and functional data improving the interpretation accuracy in oncologic patients [68]. Initial data on esophageal cancer with hybrid PET/CT are limited, but have shown a significant reduction in uncertainty of image interpretation which improves the distinction between benign and malignant causes for FDG-PET positive sites [69].…”

“…Worldwide, CT scanning of the neck, chest, abdomen, and pelvis remains the single most frequently used study for the evaluation and follow-up of esophageal cancer. Newer modalities such as PET and hybrid PET-CT have added to the pre-eminent role of endoscopic ultrasound (EUS) [3][4][5][6]. MRI currently plays a lesser role, but recent developments in lymph node contrast agents and combination with endoscopic techniques may enhance its distinctive capabilities.…”