Peritoneal lavage cytology is regarded as a useful diagnostic test for detecting intraperitoneal micrometastsis. However, there are currently no reports about cytological examination with ThinPrep(R) (CY), a newly introduced fluid-based diagnostic system, in patients with advanced gastric cancer (AGC). This study was performed to analyze the clinical significance of intraoperative peritoneal lavage for CY in AGC patients.

424 AGC patients were suspected to have serosal exposure macroscopically during surgery and they underwent intraoperative peritoneal lavage for CY between 2001 and 2006 at Korea Cancer Center Hospital. The clinical data, pathological data and CY results were collected and analyzed retrospectively.

The percentage of cytology positive results was 31.1%, and this was well correlated with the T-stage, N-stage and P-stage. The 3-year survival rates of CY0 and CY1 were 68.1% and 25.9%, respectively. According to the P-stage and CY, the 3-year survival rates were 71.1% in P0CY0, 38.9% in P0CY1, 38.5% in P1/2/3CY0 and 11.0% in P1/2/3CY1. Interestingly, both the P0CY1 and P1/2/3CY0 survival curves were similar figures, but they were significantly different from those of the other groups. Multivariate analysis indicated that CY was an independent, strong prognostic factor for survival, as well as sex, the T-stage, N-stage, P-stage, other metastasis and the serum CEA. CY1 was revealed as a risk factor for peritoneal recurrence in the curative resection group.

The results certify indirectly that cytological examination using ThinPrep(R) is a very reliable diagnostic method for detecting intraperitoneal micrometastasis from the fact that it is not only a strong prognostic factor, but it is also a risk factor for peritoneal recurrence in AGC patients. Therefore intraoperative peritoneal lavage should be included in the routine intraoperative staging workup for AGC, and its result will provide a good target for the treatment of peritoneal micrometastasis.