Surveillance for gastrointestinal malignancies

Abstract

Gastrointestinal (GI) malignancies are notorious for frequently progressing to advanced stages even in the absence of serious symptoms, thus leading to delayed diagnoses and dismal prognoses. Secondary prevention of GI malignancies through early detection and treatment of cancer-precursor/premalignant lesions, therefore, is recognized as an effective cancer prevention strategy. In order to efficiently detect these lesions, systemic application of screening tests (surveillance) is needed. However, most of the currently used non-invasive screening tests for GI malignancies (for example, serum markers such as alpha-fetoprotein for hepatocellular carcinoma, and fecal occult blood test, for colon cancer) are only modestly effective necessitating the use of highly invasive endoscopy-based procedures, such as esophagogastroduodenoscopy and colonoscopy for screening purposes. Even for hepatocellular carcinoma where non-invasive imaging (ultrasonography) has become a standard screening tool, the need for repeated liver biopsies of suspicious liver nodules for histopathological confirmation can't be avoided. The invasive nature and high-cost associated with these screening tools hinders implementation of GI cancer screening programs. Moreover, only a small fraction of general population is truly predisposed to developing GI malignancies, and indeed needs surveillance. To spare the average-risk individuals from superfluous invasive procedures and achieve an economically viable model of cancer prevention, it's important to identify cohorts in general population that are at substantially high risk of developing GI malignancies (risk-stratification), and select suitable screening tests for surveillance in these cohorts. We herein provide a brief overview of such high-risk cohorts for different GI malignancies, and the screening strategies that have commonly been employed for surveillance purpose in them.

Keywords: Biomarkers; Cancer prevention; Gastrointestinal malignancies; Screening; Surveillance.

Figure 1

Risk stratification is a step-wise approach towards identifying high-risk individuals where surveillance for gastrointestinal cancers is truly needed in order to detect any neoplastic growth at early stages. The initial step is to define a target population (Y) in the general population (X) where screening strategies would be applied. Based upon findings of the screening tests in target population, subjects deemed to be at high-risk for developing a gastrointestinal (GI) malignancy (Z) would need repeated screening tests at suitable intervals (surveillance), and this would result in detection of potentially curable early stage cancerous lesions in certain individuals (C).