| Abstract: |
The overall 5-year survival of esophageal cancers is estimated to be 10–20%. More than 90% of cancers are either squamous cell carcinoma or adenocarcinoma. Patients with esophageal cancer often present with nonspecific symptoms such as weight loss, hoarseness, coughing, or dysphagia. Esophageal cancer is normally staged according to the recommendations of the American Joint Commission on Cancer or TNM classification. There are several imaging modalities used in the evaluation of patients with esophageal cancer including a barium-swallow examination, endoscopy, EUS, CT, and PET. Endoscopy is often suggested for the anatomic evaluation of localized esophageal cancer. EUS has the ability to view the esophagus and delineate the layers of the esophageal wall affecting preoperative management. CT is the imaging modality of choice to define vascular supply and direct surgical resection approach. CT is also useful in the evaluation of metastatic disease. [18F]FDG-PET and PET/CT are not used to detect early stage disease or to evaluate the T stage. Although fusion [18F]FDG-PET/CT is more sensitive and more specific for the detection of lymph node metastasis, the main role of [18F]FDG-PET is in the detection of metastatic disease. Moreover, several studies have reported a relationship between [18F]FDG SUV max and survival. However, there is no agreement if SUV max can be an independent risk factor. The usefulness of [18F]FDG-PET in response assessment remains investigational at this time. [18F]FDG-PET is the most sensitive and specific imaging modality for staging and evaluating response to therapy of nodal and extranodal sites of malignant lymphoma. With regard to lymphomatous bowel involvement, CT scanning is useful to characterize lymphomatous involvement of the bowel, while [18F]FDG-PET/CT is used not only to detect lymphomatous bowel involvement but also to differentiate between viable residual and recurrent disease in the bowel versus scar tissue after therapy. Other less common forms of NHL commonly arise in or involve the gastrointestinal tract and can be evaluated and followed up by [18F]FDG-PET/CT scanning as well. Adenomatous polyps have the potential for malignant transformation and have been shown to accumulate [18F]FDG. [18F]FDG-PET/CT scans may therefore be a potential option for patients for whom bowel preparation, barium enema study, and/or colonoscopy are potentially problematic. Moreover, [18F]FDG-PET/CT has shown to be a sensitive, noninvasive, and easily tolerated procedure for diagnosing metastases involving the bowel. Gastrointestinal stromal tumor (GIST) is a rather uncommon tumor of the gastrointestinal (GI) tract, accounting for only up to 3% of gastrointestinal neoplasms. Standard imaging studies such as CT and MRI are useful to establish the location and size of lesions and the absence or presence of metastatic disease. [18F]FDG-PET can provide information regarding the locations of lesions and the presence and extent of metastatic disease, but it does not contribute to the specific diagnosis of GIST. A definitive diagnosis of GIST requires tissue sampling. Metabolic response to imatinib, a tyrosine kinase inhibitor designed for the molecular therapy of GIST, could be demonstrated by [18F]FDG-PET as early as 24 h after a single dose of the drug. [18F]FDG-PET can separate responders from nonresponders early on within 1 week of treatment, and the progression-free survival is significantly better in patients who show a metabolic response by [18F]FDG-PET. Moreover, during follow-up, PET can demonstrate the development of secondary resistance to imatinib by identifying the reappearance of focal [18F]FDG uptake within the existing tumor mass. © Springer Science+Business Media New York 2013. All rights are reserved. |
