Because patients are often asymptomatic or experience nonspecific symptoms, esophageal cancer is frequently discovered at an advanced stage and therefore is one of the most lethal cancers.1 The 5-year survival rate is only 15%.1 Although esophageal cancer is uncommon, in the Western world it has the fastest rate of increase of any malignancy.1 Squamous cell cancers are the most common type of esophageal cancer worldwide; however, in the United States, the incidence of squamous cell cancer is decreasing–probably due to declining rates of smoking–whereas rates of adenocarcinoma of the distal esophagus and gastroesophageal junction are increasing dramatically.2 This may be attributable to rising rates of obesity, which predisposes to gastroesophageal reflux disease (GERD), a condition associated with an almost 8-fold higher risk of esophageal adenocarcinoma.2,3 Self-treatment of GERD with OTC medications may mask symptoms of esophageal cancer, contributing to a delay in diagnosis.4 GERD may also contribute to the development of Barrett’s esophagus, a precursor of esophageal adenocarcinoma in which a metaplastic process replaces normal esophageal mucosa with columnar epithelium.2 Although surgery offers the best chance of curing esophageal cancer, only 25% of patients present with resectable disease, and postsurgical quality of life may be severely compromised.5,6 Improving the outcomes of esophageal cancer therefore relies on earlier diagnosis and development of more effective treatments.
Opportunities for Early Diagnosis
Endoscopic examination plays a key role in surveillance of patients with Barrett’s esophagus and diagnosis of esophageal cancer, but the low incidence of this malignancy—only 17,000 new cases annually in the United States—precludes broad screening programs.7-9 In patients with Barrett’s esophagus, surveillance has been shown to detect esophageal cancer at early stages and to improve survival.10 However, few patients with esophageal cancer have been diagnosed with Barrett’s esophagus, and the incidence of esophageal cancer in those with Barrett’s esophagus is <1%; therefore, surveillance has little impact on overall esophageal cancer mortality.10,11 A cohort study found that eight factors—advanced age, smoking, obesity, dysphagia, hematemesis, abdominal pain, appetite loss, weight loss, and anemia—were independent risk factors for the presence of esophageal cancer and may identify patients for whom endoscopy is appropriate.12
New techniques may one day add to the diagnostic power of endoscopy. Narrow band imaging (NBI) employs filters with central wavelengths of 415 nm and 540 nm and bandwidth of 30 nm.13 It can clearly visualize microvascular structures and has been shown to be superior to endoscopic white light imaging for detection of superficial cancer in patients with a history of esophageal squamous cell cancer.13 Probe-based confocal laser endomicroscopy provides microscopic views of the mucosa and can reveal cellular details during the endoscopic procedure, allowing diagnosis in the endoscopy laboratory.14 When combined with high-definition white light endoscopy, it is better able to identify neoplasms in patients with Barrett’s esophagus than white light endoscopy alone.14