Pet Imaging in Esophageal Carcinoma

www.onk.ns.ac.rs/Archive Vol 20, No. 3-4, December 2012 PET IMAGING IN ESOPHAGEAL CARCINOMA Esophageal carcinoma is a relatively rare disease with approximately 13,200 new cases detected in 2001 in the United States (1). It is most common between 50 and 60 years of age with a male to female ratio of 4:1 (2). According to the SEER database, an annual age-adjusted incidence rate is 4.5 per 100,000 men and women. Esophageal cancer is a highly lethal neoplasm with the reported annual age-adjusted mortality rate of 4.3 per 100,000 men and women (3). For the period between 2001 and 2007, in less than 25% of patients who were diagnosed without nodal involvement, the 5-year relative survival was 37.3%; while in 32% of those diagnosed with regional nodal involvement or documented metastatic disease, the 5-year survival was 18.4%, and 3.1%, respectively (2). The gold standard for conventional staging in esophageal cancer includes CT and endoscopic ultrasound (EUS) with associated biopsy of the mucosa. The depth of tumor invasion is usually assessed by combination of esophagogastroduodenoscopy and endosonography. This approach evaluates extent of mucosal involvement and peritumoral nodal metastases, but is limited in patients with stenoses and strictures due to incomplete passage of the endoscope. CT may detect both local invasion of neighboring mediastinal structures and regional nodal and distal metastases (4). CT is less sensitive, however, for detection of regional and distant metastases compared to FDG PET. FDG PET or FDG PET/CT imaging has a significant role in primary staging of esophageal cancer (5-12). FDG PET provides more accurate staging and more accurate prognostic stratification than CT alone. It may alter the treatment strategy in more than 30% of patients (9, 12). Nevertheless, both FDG PET and CT are not able to detect small esophageal metastases. On CT examination, in most cases, a 10 mm cutoff is used for abnormal lymph nodes, while FDG PET usually cannot detect lesions smaller than 5 mm due to a spatial resolution of 3 mm-5 mm. Although FDG PET is not highly sensitive, with a reported range between 22%-76%, it has high specificity for detection of locoregional lymph node metastases (about 90%) (1). FDG PET and FDG PET/CT are limited in detection of peritumoral nodal disease (5, 8, 13). It is of limited value in assessment of regional lymph node involvement, whereas EUS has the highest sensitivity of 70%-90% (14). It has been shown that F-FDG is a good radiotracer to image esophageal cancer compared to other agents, such as F-FLT and C-choline (15, 16). Jager et al. compared FDG-PET with 11-C-choline PET for evaluation of mediastinal lymph nodes and reported FDG PET sensitivity of 100% versus 73% for C-choline (15). In esophageal cancer, Westreenen et al. showed that the uptake of F-FDG was significantly higher than F-FLT. FLT is, however, useful to image signet ring cell gastric cancer whereas FDG-PET has reduced sensitivity (16). Detection of distant metastases in esophageal carcinoma is a key fact in determining treatment strategy. Luketich reported FDG PET sensitivity and specificity of 69% and 93%, respectively, compared to only 46%, and 74%, respectively, for CT (17). FDG PET showed higher sensitivity and specificity of 78% and 90%, respectively compared to 46% and 69% for combined CT imaging and endosonography (13). Heeren et al. reported that the sensitivity of detecting distant nodal and systemic metastases was greater with FDG PET compared to CT/EUS alone (78% vs. 37%, respectively) (6). At the Third German Interdisciplinary Consensus Conference, FDG PET was classified as an essential component for the N and M staging in esophageal Positron emission tomography in neoplasms of the digestive system