| Gastric carcinoma has been the leading cause of cancer death world wide in the latest twenty years. It now ranks second only to lung cancer with an estimated 755,500 new cases diagnosed annually around the world. It is estimated that 21,900 new cases are diagnosed annually, with approximately 13,500 deaths per year. The prognosis for this disease remains poor. The overall 5-year survival rate in most of the areas ranges from 5% to 15%. Death from gastric carcinoma after curative resection is mostly due to recurrence or/and matastases. The only proven , potentially curative treatment is surgical resection of all gross and microscopic disease. Even after a "curative" gastrectomy , disease recurs in both regional and distant sites in at least 80% of patients. The most common recurrence or metastases is peritoneal dissemination, which represents 33% to 50% of total recurrence after curative gastrectomy. The removal of a gastric cancer by surgery utilizing an extended lymphadenectomy is only a small part the required intraoperative surgical management of gastric cancer. Gastrectomy generally is not indicated for cases of severe peritoneal dissemination because it does not improve prognosis and can impair the patient's quality of life.Accordingly, the accurate prediction of peritoneal dissemination is essential to ensure appropriate surgical referral or to plan appropriate treatments including intraperitoneal chemotherapy and hyperthermia. However the early prediction of micro peritoneal dissemination is very difficult using current diagnostic tools such as computed tomography, ultrasonography , laparoscopy or various tumor markers. There has been no good predictor of peritoneal recurrence after curative resection except for peritoneal washing cytolopy (PWC). Unfortunately, the sensitivity of PWC is low (30%), and it is crucial to development a new methods to predict peritoneal recurrence and metastases.The recent identification of genes overexpressed in gastric cancer, combined with advances in molecular biology, provides the opportunity to establish moresensitive, specific, and cost-effective ways of identifying metastatic disease. Among the current possibilities, one of the most compelling is the development of a sensitive molecular diagnostic assay for the detection of gastric cancer in the peritoneal cavity. Such an assay could potentially replace invasive procedures as peritoneal biopsy by laparoscopy and / or be used for gastric cancer screening and monitoring treatment responses. Unfortunately, molecular analysis of peritoneal washing has proven more challenging than that of other tissue compartments. mRNA is relatively unstable in peritoneal washing, and the presence of protein can inhibit the PCR reaction. Other issues include the relatively low concentration of exfoliated cancer cells in peritoneal cavity and false-positive results in illegitimating transcription in peritoneal cells, including leukocytes, mesothelial cells and etc.The intermediate filament proteins of CK19 and CK20 are specific markers that are normally not expressed in lymphoid, CEA hematopoietic tissues and peritoneal washing. CK19mRNA, CK20 mRNA and CEA mRNA detected by RT-PCR have been used as index of disseminated tumor cells in blood , bone marrow, lymph nodes and peritoneal washing in patients with gastric cancer and other epithelial cancers including lung, pancreas and breast.In preliminary experiment, we used strict precautions to avoid contamination with peritoneal cells at collection and an optimally calibrated assay to eliminate false-positive in control peritoneal washing samples (0/4). We then applied the assay to peritoneal samples from 67 patients with gastric carcinoma and 9 cases begin gastric disease.Background and objectivesDeath from gastric carcinoma after curative resection is mostly due to recurrence and matastases. The most common recurrence and matastases is peritoneal dissemination after curative gastrectomy. The accurate prediction of peritoneal micro metastasis is very difficult using current diagnostic tools with low sensitivity. The objective of this study was to develop a sensitive method for detecting minimal residual disease in the peritoneal cavity by carcinoembryonic antigen (CEA) mRNA,cytokeratin (CK) 19mRNA, CK20mRNA using nested reverse transcription-polymerase chain reaction (RT-PCR), and clarify the clinicopathologic characteristics of micro metastases in the peritoneal cavity to determine the treatment options in gastric cancer.Materials and methodsAmong 67 cases of gastric carcinoma and 9 cases benign gastric disease, the abdominal cavities were washed with 200ml normal saline and 50ml was aspirated from the pouches of Douglas and centrifuged. The expressions of CK19, CK20 and CEA were detected at mRNA level with nested RT-PCR and at protein level by time resolved fluoroimunoassay (TRF). At the same time peritoneal washing cytology examinations (PWC) were carried out by routine methods.ResultsPositive expressions of CK19 mRNA, CEA mRNA , P-CEA, PLC and CK20 mRNA were 62.7%, 52.2%, 35.8%, 31.3%, 34.3% respectively. The expression of CK19 mRNA and CEA mRNA were significantly higher than P-CEA and PLC (PO.01), which showed the positive expression of CK19 mRNA and CEA mRNA were relative to depth of tumor invasion and TNM staging. The positive rates of CEAmRNA and CK19 mRNA expression increased with the depth of invasion, staging of the disease and serosal involvement. However, there was no significant correlation between COO mRNA and clinicopathologic characteristics. All cases with positive PLC presented CEA mRNA (+) and CK 19 mRNA (+), while 14 and 21 of 46 case with negative PLC proved to be CEA mRNA (+) and CK19 mRNA (+), respectively. Combination detection with CK19 mRNA and CEA mRNA can improve the positive rates as 74.6%.None of 9 patients with benign gastric disease were positive.ConclusionTo detect CEA and CK19 in peritoneal washing by nested RT-PCR, P- CEA by...
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