Positive Occult Blood and Negative Colonoscopy – Should We Perform Gastroscopy?

Abstract

Colorectal cancer (CRC) is the fourth most commonly diagnosed type of cancer and the second leading cause of cancer death in Canada. It has been estimated that there will be 20,800 new cases of CRC in Canada in 2007 and 8700 deaths (1). Overall, Canadian men have a one in 14 lifetime risk and women have a one in 12 lifetime risk of developing CRC; these risks are among the highest worldwide. The five-year survival rate for early cancer is more than 90%, but this number falls to below 10% for those diagnosed with widespread disease (2). Early cancers and precancerous polyps are often asymptomatic, and because early diagnosis and treatment may significantly affect prognosis, there is strong support for population screening for CRC. CRC screening has also been shown to be cost effective, with a cost of less than US$20,000 per life saved compared with no screening (3). Screening with fecal occult blood testing (FOBT) followed by colonoscopy for positive FOBT, reduces CRC mortality by 15% to 33% (4–6). There is no formal screening program for CRC in Canada, but the National Committee on Colorectal Cancer Screening, supported by Health Canada, recommends biennial FOBT for individuals aged 50 to 74 years (7). If the test is positive, then a follow-up test (usually colonoscopy, but possibly flexible sigmoidoscopy and/or barium enema depending on local resources) should be performed. In a screening population, approximately 40% of positive FOBT will lead to a positive diagnosis (CRC or adenoma) at the time of colonoscopy (8,9). It is reasonable to assume that some cases of positive FOBT with negative colonoscopy may be due to an upper gastrointestinal (GI) malignancy. Therefore, should we be performing a gastroscopy on all patients who have a negative colonoscopy following positive FOBT? No method of screening for gastric cancer has been shown to be cost-effective or reliable in Western countries in detecting potentially curable disease. To date, there are no formal guidelines on whether routine esophagogastroduodenoscopy (EGD) should be performed for FOBT-positive, colonoscopy-negative patients.