Diagnostic Laparoscopy with 5-Aminolevulinic-Acid-Mediated Photodynamic Diagnosis Enhances the Detection of Peritoneal Micrometastases in Advanced Gastric Cancer

Recently, we reported that diagnostic laparoscopy with photodynamic diagnosis using oral 5-aminolevulinic acid (ALA-PDD) is a promising tool for diagnosing early peritoneal metastases in gastric cancer. The present study evaluated the usefulness of adding ALA-PDD to conventional diagnostic laparoscopy and assessed the association of the ALA-PDD results with peritoneal fluid cytology and molecular diagnostic testing.Diagnostic laparoscopy using sequential white light (WL) and ALA-PDD observations was performed in 52 advanced gastric cancer patients, and the sensitivity of ALA-PDD for detecting peritoneal disease was compared to WL. Peritoneal fluid samples from the same patients were also subjected to cytological examination and molecular diagnosis using a transcription-reverse transcription concerted reaction (TRC).Twenty-four of the 52 patients (46%) had no macroscopic evidence of peritoneal metastases on WL examination; however, ALA-PDD detected dissemination in 5 of these 24 patients (21%) (pd-P). Cytological examination was negative in 4 of the 5 pd-P patients, and molecular testing using TRC was negative in 3 of the 5 pd-P patients.This study demonstrated that diagnostic laparoscopy with ALA-PDD improved the sensitivity for the detection of peritoneal metastases. ALA-PDD may be a useful technique for the preoperative staging of advanced gastric cancer and can complement examinations of peritoneal lavage fluids.