The detection of gastric cancer cells in intraoperative peritoneal lavage using the reverse transcription–loop-mediated isothermal amplification method

IntroductionTo detect a small number of malignant cells, we used a highly sensitive detection system that measures the expression levels of cytokeratin (CK) 19 messenger RNA by reverse transcription–loop-mediated isothermal amplification (RT–LAMP).Materials and methodsWe evaluated the clinical relevance of our novel diagnostic method with an RT–LAMP assay using CK19 as a target gene for the detection of free cancer cells in peritoneal lavage and assessed the clinical significance of the molecular diagnosis by survival analysis and frequency of recurrence, with a median follow-up period of 39 mo. We observed 52 patients with gastric cancer who underwent gastrectomy, bypass operation, and exploratory laparotomy.ResultsThose 52 patients, who were subjected to both RT–LAMP and cytologic examination, were divided into the following three groups: (1) patients positive by cytology and RT–LAMP (CY+/LAMP+) (n = 9), (2) patients positive by LAMP and negative by cytology (CY−/LAMP+) (n = 12), and (3) patients negative by both cytology and LAMP (CY−/LAMP−) (n = 31). All patients with simultaneous peritoneal dissemination and positive cytology were positive on RT–LAMP. The results of RT–LAMP were statistically significant for recurrence by univariate analysis (P < 0.005). Cytology-positive cases had a very poor prognosis, and RT–LAMP-positive cases had a worse prognosis than RT–LAMP-negative cases.ConclusionsOur findings suggest that CK19 RT–LAMP would be useful as an intraoperative diagnostic modality to detect patients with a high risk of recurrence even after clinically curative surgery, who thus require proper adjuvant therapy.