Topic Highlight
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Aug 7, 2015; 21(29): 8769-8775
Published online Aug 7, 2015. doi: 10.3748/wjg.v21.i29.8769
Clinical applications of 5-aminolevulinic acid-mediated fluorescence for gastric cancer
Tsutomu Namikawa, Tomoaki Yatabe, Keiji Inoue, Taro Shuin, Kazuhiro Hanazaki
Tsutomu Namikawa, Kazuhiro Hanazaki, Department of Surgery, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
Tomoaki Yatabe, Department of Anesthesiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
Keiji Inoue, Department of Urology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
Taro Shuin, Department of Urology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
Author contributions: Namikawa T and Shuin T designed the research; Namikawa T and Inoue K performed the research; Namikawa T and Yatabe T analyzed the data; Namikawa T drafted the manuscript; and Hanazaki K made critical revisions.
Conflict-of-interest statement: The authors have no conflict of interest related to the manuscript.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Tsutomu Namikawa, MD, Department of Surgery, Kochi Medical School, Kohasu, Oko-cho, Nankoku, Kochi 783-8505, Japan. tsutomun@kochi-u.ac.jp
Telephone: +81-88-8802370 Fax: +81-88-8802371
Received: February 23, 2015
Peer-review started: February 26, 2015
First decision: April 23, 2015
Revised: May 18, 2015
Accepted: June 26, 2015
Article in press: June 26, 2015
Published online: August 7, 2015
Processing time: 165 Days and 19.9 Hours
Abstract

5-aminolevulinic acid (ALA) is a naturally occurring amino acid that is a protoporphyrin IX (PpIX) precursor and a next-generation photosensitive substance. After exogenous administration of ALA, PpIX specifically accumulates in cancer cells owing to the impaired metabolism of ALA to PpIX in mitochondria, which results in a red fluorescence following irradiation with blue light and the formation of singlet oxygen. Fluorescence navigation by photodynamic diagnosis (PDD) using ALA provides good visualization and detection of gastric cancer lesions and is a potentially valuable diagnostic tool for gastric cancer for evaluating both the surgical resection margins and extension of the lesion. Furthermore, PDD using ALA might be used to detect peritoneal metastases during preoperative staging laparoscopy, where it could provide useful information for the selection of a therapeutic approach. Another promising application for this modality is in the evaluation of lymph node metastases. Photodynamic therapy (PDT) using ALA to cause selective damage based on the accumulation of a photosensitizer in malignant tissue is expected to be a non-invasive endoscopic treatment for superficial early gastric cancer. ALA has the potential to be used not only as a diagnostic agent but also as a therapeutic drug, resulting in a new strategy for cancer diagnosis and therapy. Here, we review the current use of PDD and PDT in gastric cancer and evaluate its future potential beyond conventional modalities combined with a light energy upconverter, a light-emitting diode and near-infrared rays as light sources.

Keywords: Fluorescence imaging; 5-aminolevulinic acid; Photodynamic diagnosis; Photodynamic therapy; Gastric cancer

Core tip: 5-Aminolevulinic acid (ALA) is a naturally occurring amino acid that is a protoporphyrin IX precursor and a next-generation photosensitive substance. Fluorescence navigation by photodynamic diagnosis (PDD) using ALA is a potentially valuable diagnostic tool for gastric cancer for evaluating both the surgical resection margins and the extension of the lesion. Furthermore, PDD using ALA might be useful to detect peritoneal metastases during preoperative staging laparoscopy and evaluation of lymph node metastases. Photodynamic therapy using ALA to cause selective damage based on the accumulation of a photosensitizer in malignant tissue is expected to become a non-invasive endoscopic treatment for superficial early gastric cancer.