A Randomized Study Comparing Autofluorescence Imaging(AFI) Followed by Narrow Band Imaging(NBI) With Videoendoscopy for the Detection of High Risk Lesions of Stomach (CAFBI)

Gastric cancer remains one of the leading causes of cancer deaths worldwide. Early detection and diagnosis of gastric cancer improves the outcomes of treatment. However, most of gastric cancers detected in Singapore are late and advanced in stages.

Videoendoscopy is the standard tool for examination of gastrointestinal tract. Despite the improvement of technology, early gastric cancers can be easily missed by routine examination, because there are few morphological changes. Therefore, a functional imaging modality, that can distinguish abnormal lesion from surrounding normal mucosa may complement the current videoendoscopy.

Autofluorescence Imaging (AFI) based on the presence of natural tissue fluorescence on the gastrointestinal tract. When the mucosa was exposed by an excitation light, certain endogenous molecules (fluorophores) will emit fluorescence light of longer wavelength. The fluorescent light can be detected and spectrally analyzed. By computation of the difference in the reflecting images, the system can specify lesions, including malignancies from the adjacent mucosa, and can reveal early cancers that are not detectable by standard endoscopy.

Narrow band imaging (NBI) is another novel optical imaging technique based on high resolution imaging, which aims at enhancing the fine structure of the mucosa. In NBI, the band widths of the red, blue, green components of the excitation light are narrowed to certain wavelength ranges, which allow better contrast of the superficial mucosa and the vascular structure. NBI has a maximum zoom capacity of 115 times. Abnormal lesions are detected by the presence of abnormal mucosal and vascular patterns.

Recent studies suggested that these AFI and NBI systems can be complementary to each other. The resolution of AFI is low but it can be used as a 'red flag' technique to screen any suspicious lesions from the normal mucosa. On the other hand, NBI produces high resolution images which allows detailed examination and subsequent target biopsy of the suspicious lesions based on AFI. Preliminary reports from Japan and the Netherlands suggested this combined imaging method improves the detection of early esophageal and gastric cancers. Recently, a new endoscopy system has been developed that incorporates standard videoendoscopy system with both AFI and NBI modes. By pressing a switch, the endoscopy system can switch from normal white light to either a narrow band light or autofluorescence mode. This novel system reduces the convenience and discomfort for the patients to avoid repeated intubation. The purpose of this study is to prospectively evaluate this combined imaging modality for detection of high risk gastric lesions and early cancers by comparing it with standard videoendoscopy in a randomized fashion.