DETECTION OF OCCULT LYMPH NODE TUMOR CELLS IN NODE-NEGATIVE GASTRIC CANCER PATIENTS

ABSTRACT Background: The presence of lymph nodes metastasis is one of the most important prognostic indicators in gastric cancer. The micrometastases have been studied as prognostic factor in gastric cancer, which are related to decrease overall survival and increased risk of recurrence. However, their identification is limited by conventional methodology, since they can be overlooked after routine staining. Aim: To investigate the presence of occult tumor cells using cytokeratin (CK) AE1/AE3 immunostaining in gastric cancer patients histologically lymph node negative (pN0) by H&E. Methods: Forty patients (T1-T4N0) submitted to a potentially curative gastrectomy with D2 lymphadenectomy were evaluated. The results for metastases, micrometastases and isolated tumor cells were also associated to clinicopathological characteristics and their impact on stage grouping. Tumor deposits within lymph nodes were defined according to the tumor-node-metastases guidelines (7th TNM). Results: A total of 1439 lymph nodes were obtained (~36 per patient). Tumor cells were detected by immunohistochemistry in 24 lymph nodes from 12 patients (30%). Neoplasic cells were detected as a single or cluster tumor cells. Tumor (p=0.002), venous (p=0.016), lymphatic (p=0.006) and perineural invasions (p=0.04), as well as peritumoral lymphocytic response (p=0.012) were correlated to CK-positive immunostaining tumor cells in originally negative lymph nodes by H&E. The histologic stage of two patients was upstaged from stage IB to stage IIA. Four of the 28 CK-negative patients (14.3%) and three among 12 CK-positive patients (25%) had disease recurrence (p=0.65). Conclusion: The CK-immunostaining is an effective method for detecting occult tumor cells in lymph nodes and may be recommended to precisely determine tumor stage. It may be useful as supplement to H&E routine to provide better pathological staging.

Occult tumor cells in peritoneal lavage in pancreatic carcinoma patients.

e14556 Background: Pancreatic carcinoma is one of the most aggressive malignancies with a poor prognosis. Assessment of occult tumor cells could prevent aggressive surgery in patients with metastatic spread. The aim of this study was to investigate the prognostic significance of occult tumor cells in peritoneal lavage of patients with pancreatic carcinoma. Methods: This was a prospective study to assess the presence of occult tumor cells in peritoneal lavage of 96 pancreatic carcinoma patients at the time of surgery using real-time RT-PCR for carcinoembryonic antigen (CEA), epidermal growth factor receptor 1 (EGFR1) and human telomerase (hTERT). Gene expression of tested markers was correlated with clinical/pathological characteristics using Kruskal-Wallis Anova and Mann-Whitney tests. Kaplan-Meier methods and Gehan-Wilcoxon tests were used for overall survival analyses. Results: Overall, 65 of 96 (69.9%) pancreatic carcinoma patients died, the overall survival median was 10.3 months. A significant association between CEA expression in peritoneal lavage and the clinical stage was found (p<0.03). In addition, patients with high grade tumors had significantly higher expression of EGFR in peritoneal lavage compared to patients with low grade tumors (p<0.04). The patients with the presence of occult cancer cells detected in the peritoneal lavage using CEA and/or EGFR had significantly shorter overall survival (p<0.001; HR=2.14 [95% CI: 1.30-3.55]) with overall survival median 6.8 months. Conclusions: These data demonstrate that the presence of occult tumor cells in peritoneal lavage is a negative prognostic factor in pancreatic carcinoma patients. Occult tumor cells detection using PCR based methods can identify patients with advanced disease for whom radical surgery is of no benefit. Prospective studies should confirm usefulness of this method for the selection of patients for radical surgery. Acknowledgements: Supported by grants IGA MZ NS 9937‑4, MPOTIP FR-TI1/525, IGA UP LF_2011_018 and CZ.1.05/2.1.00/01.0030.

Assessment of Minimal Residual Disease in Ewing Sarcoma

Advances in molecular pathology now allow for identification of rare tumor cells in cancer patients. Identification of this minimal residual disease is particularly relevant for Ewing sarcoma, given the potential for recurrence even after complete remission is achieved. Using RT-PCR to detect specific tumor-associated fusion transcripts, otherwise occult tumor cells are found in blood or bone marrow in 20–30% of Ewing sarcoma patients, and their presence is associated with inferior outcomes. Although RT-PCR has excellent sensitivity and specificity for identifying tumor cells, technical challenges may limit its widespread applicability. The use of flow cytometry to identify tumor-specific antigens is a recently described method that may circumvent these difficulties. In this manuscript, we compare the advantages and drawbacks of these approaches, present data on a third method using fluorescent in situ hybridization, and discuss issues affecting the further development of these strategies.