Endoscopy recommended for early diagnosis of GI cancer
Endoscopy is the gold standard for the early diagnosis of gastrointestinal (GI) cancer, according to Dr. Yim Heng Boon, senior gastroenterologist and hepatologist consultant with the Mount Elizabeth Novena Specialist Centre in Singapore.
“Our main aim … is to diagnose cancer early so that we can offer curative endoscopic or open surgery for these patients,” said Boon. The speaker discussed that popular tests for screening of GI cancers include serum tumor markers, radiological imaging and endoscopy.
The American Society of Clinical Oncology and the European Group on Tumor Markers stated that the tumor markers carcinoembryonic antigen (CEA) and cancer antigen (CA) 19-9 should not be used as a screening tool for colorectal or pancreatic cancer. Boon explained that in order for a tumor marker to be ideal, it should be highly specific and sensitive, provide a lead time over clinical diagnosis, correlate reliably with tumor burden, have a short life to allow serial measurement, and must be cheap and acceptable.
“Unfortunately, there is no such ideal tumor marker at this point,” said Boon. “Many times, it is slightly elevated, causing much anxiety.”
Radiologic tests also have limited utility in the early diagnosis of gastrointestinal cancer, added Boon. The US Multi-Society Task Force on Colorectal Cancer, the American Cancer Society, and the American College of Radiology have released recommendations that computed tomography (CT) colonography may be used for screening asymptomatic adults more than 50 years old with average risk for colon cancer. However, it is not recommended for patients with history of polyps on prior colonoscopy or those with increased risk of colon cancer. In contrast, the US Preventive Services Task Force stated that there is insufficient evidence to support the use of CT colonography as a screening test because of missed detection of polyps less than 5 mm, lack of local expertise, inadequate standardization in performing and interpreting the test, and the risk of radiation incurred during the test.
“Endoscopy is still the best or gold standard to detect early cancers of the GIT,” stressed Boon. “Majority of the colon cancers arise from polyps, so by doing surveillance colonoscopy, we can reduce the incidence of colon cancer,” he added
There are many endoscopic techniques currently available aside from conventional gastroscopy. Chromoendoscopy utilizes stains to improve characterization and tissue localization during endoscopy. Optical coherence tomography has a high resolution to view microscopic tissue structures; however, the depth of penetrance is limited. Endoscopic ultrasound has its utility in visualizing the layers of the gastrointestinal wall. Confocal microendoscopy provides images that are enlarged 1000 times, allowing the physician to view cellular details of suspicious lesions. Video capsule endoscopy is useful in patients with obscure GI bleeding, suspected Crohn’s disease, small bowel tumors, small injury with NSAIDs use and suspected celiac disease.