AIM:To investigate the utility of photodynamic diagnosis(PDD) using 5-aminolevulinic acid(5-ALA) to detect gastric/colorectal tumors.METHODS:This prospective single-center study investigated inter-subject variability in patients with early-stage gastric/colorectal tumor indicated for endoscopic resection.Subjects were patients with gastric or colorectal tumors who had undergone endoscopic resection between November 2012 and November 2013.Selection criteria included age 20-80 years,either sex,and provision of informed consent.Patients were orally administered 20 mg/kg of 5-ALA enteric-coated capsules(SBI ALApromo Co.,Tokyo,Japan).Administration of5-ALA was followed by endoscopic resection of gastric or colorectal tumors,and the resected specimens were examined using a video autofluorescence processor and a fluorescence endoscope(SAFE-3000 and EB-1970 AK,respectively;Pentax,Tokyo,Japan).The primary endpoint was the presence of fluorescence in tumors.Endoscopic,macroscopic,and histopathologic findings of tumors were assessed.We also evaluated adverse events of the present procedure as a secondary endpoint and examined each patient for the presence of known adverse effects of 5-ALA,namely,hematocytopenia,liver dysfunction,hypotension,nausea,and photosensitivity.RESULTS:We enrolled 10 patients(7 men,3 women)(n = 13 lesions:10 gastric/3 colorectal tumors).Fluorescence was detected in 7/13(53.8%) lesions.No significant differences in sex(male:55.6%vs female:50.5%,P = 1.00),age(67.1 ± 1.9 years vs 65.0 ±2.0 years,P= 0.45),tumor color(reddish:60.0%vs discolored:33.3%,P = 0.56),tumor diameter(15.0± 2.1 mm vs 14.2 ± 2.3 mm,P= 0.80),macroscopic type(protruded:70.0%vs depressed 0%,P = 0.07),histologic type(differentiated type:58.3%vs 0%,P = 0.46),invasion depth(mucosal layer:55.6%vs submucosal layer:33.3%,P = 1.00),lymphatic invasion(present:33.3%vs absent:50.0%,P= 1.00),venous invasion(present:0%vs absent:54.5%,P= 1.00) or procedure time of endoscopic resection(36.3 ± 8.3 min vs 36.7 ± 9.0 min,P = 0.98) were observed between the patients with and without fluorescence.Fluorescence detection rate tended to be high for elevated lesions.Liver dysfunction developed in 4/10(40.0%) patients.The extent of the liver dysfunction was a slight increase in transaminases and total bilirubin levels,which spontaneously improved in the patients.None of the patients developed photosensitivity.CONCLUSION:Results of this preliminary study suggest the utility of PDD using 5-ALA for screening of gastric and colorectal cancers. AIM:To investigate the utility of photodynamic diagnosis(PDD) using 5-aminolevulinic acid(5-ALA) to detect gastric/colorectal tumors.METHODS:This prospective single-center study investigated inter-subject variability in patients with early-stage gastric/ Colorectal tumor indicated for endoscopic resection.Subjects were patients with gastric or colorectal tumors who had undergone endoscopic resection between November 2012 and November 2013.Selection criteria included age 20-80 years,either sex,and provision of informed consent.Patients were orally administered 20 Mg/kg of 5-ALA enteric-coated capsules (SBI ALApromo Co., Tokyo, Japan). Administration of 5-ALA was followed by endoscopic resection of gastric or colorectal tumors, and the resected specimens were examined using a video autofluorescence processor and a The fluorescence endpointoscope(SAFE-3000 and EB-1970 AK,respectively;Pentax,Tokyo,Japan).The primary endpoint was the presence of fluorescence in tumors.Endoscopic,macroscopic,and histopathol Ogic findings of tumors were evaluated.We also evaluated adverse events of the present procedure as a secondary endpoint and examined each patient for the presence of known adverse effects of 5-ALA,namely,hematocytopenia,liver dysfunction,hypotension,nausea,and photosensitivity. RESULTS: We enrolled 10 patients (7 men, 3 women) (n = 13 lesions: 10 gastric/3 colorectal tumors). Fluorescence was detected in 7/13 (53.8%) lesions. No significant differences in sex (male: 55.6% Vs female: 50.5%, P = 1.00), age (67.1 ± 1.9 years vs 65.0 ± 2.0 years, P = 0.45), tumor color (reddish: 60.0% vs discolored: 33.3%, P = 0.56), tumor diameter (15.0 ± 2.1 mm vs 14.2 ± 2.3 mm, P = 0.80), macroscopic type (protruded: 70.0% vs. 0%, P = 0.07), histologic type (differentiated type: 58.3% vs. 0%, P = 0.46), invasion depth (mucosal layer: 55.6% vs. submucosal layer: 33.3%, P = 1.00), lymphatic invasion (present: 33.3% vs. absent: 50.0%, P = 1.00), venous invasion (present: 0% vs absent: 54.5%, P = 1.00) or procedure time of endoscopic resection(36.3 ± 8.3 Min vs 36.7 ± 9.0 min, P = 0.98) were observed between the patients with and without fluorescence. Fluorescence detection rate tended to be high for elevated lesions. Liver dysfunction developed in 4/10 (40.0%) patients. The extent of the liver dysfunction Was a simulated increase in transaminases and total bilirubin levels, which spontaneously improved in the patients.None of the patients developed photosensitivity.CONCLUSION:Results of this preliminary study suggest the utility of PDD using 5-ALA for screening of gastric and colorectal cancers.