Intraoperative photodynamic diagnosis of lymph node metastasis in esophageal cancer patients using 5-aminolevulinic acid.

Lymph node metastasis is the strongest prognostic factor in esophageal cancer patients who have undergone esophagectomy. The accurate diagnosis of lymph node metastasis is important, but the pre-operative diagnostic accuracy is poor. The intraoperative diagnosis based on histopathological examination of frozen tissue specimens is complicated and time-consuming. Therefore, the establishment of a simple and rapid intraoperative diagnostic method is essential. Exogenous application of 5-aminolevulinic acid (ALA) causes a selective accumulation of protoporphyrin IX, which is a fluorescent substrate, in cancer cells. The present study evaluated the feasibility of photodynamic diagnosis using ALA (ALA-PDD) for lymph node metastasis in esophageal cancer. A total of 292 lymph nodes were analyzed from 8 esophageal squamous cell cancer patients treated with esophagectomy. The patients were administered ALA orally prior to surgery. Excised lymph nodes were cut in half and examined by spectrometer. The diagnostic results of ALA-PDD were compared to those of the histopathological examination. Among the 292 lymph nodes, 19 nodes (6.5%) were histologically metastatic and 21 nodes (7.2%) were PDD-positive. The sensitivity and specificity of ALA-PDD were 84.2% (16/19) and 98.2% (268/273), respectively. The area of cancer nests of the PDD-negative lymph nodes was <2 mm2. Metastatic lymph nodes, including cancer nests >4 mm2, were correctly diagnosed by ALA-PDD. In conclusion, this study demonstrated that ALA-PDD of lymph node metastasis in patients with esophageal cancer is feasible. Further investigation would make this method a simple and rapid intraoperative diagnostic tool.