Nihon Gekakei Rengo Gakkaishi (Journal of Japanese College of Surgeons)

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The radioisotope (RI) method to identify the sentinel lymph node (SLN) in gastrointestinal cancer is still under development. Although most facilities use the same gamma probe to monitor RI, no consensus has been reached on the dose of RI, measuring method, or criteria for SLN identification. In this study, we investigated the characteristics of the gamma probe with known radioactive sources and compare them with those of a well scintillation counter (autowell). In addition, we evaluated the optimum conditions for SLN identification using a gamma probe on the basis of actual measurements in patients with gastric cancer. The results of measurements of varying radioactive sources at different distances using the gamma probe indicate that the optimal radiation range, at which counts are inversely proportional to the square of the distance to the radioactive source, is 1×10^-1 μCi to 1 μCi. The proper dose of injection for clinical application can be determined by reverse calculation. Withe regard to the directivity of gamma probe, our results showed that with a lateral deviation of 2 cm from the radiation source, measurements taken at distances of 3 cm and 4 cm resulted in 8% and 13%, respectively, of the counts recorded without deviation.Therefore, the gamma probe must be positioned close to the lymph node to minimize the impact of lateral scatter;that is, measurements must be taken within 1 cm distance from the site. In clinical study for patients with early gastric cancer, there was a strong correlation between the autowell and gamma probe counts (r=0.704 : p<0.0001). The distribution of autowell and gamma probe counts was found to be nearly a linear function ; (gamma probe counts) =0.002× (autowell counts) +35.118. These results showed the gamma probe counts are reliable on the detection of SLN under adequate conditions. Recently, the Japanese Society for Sentinel Navigation Surgery has just organized to establish the diagnostic criteria for SLN identification. In order to establish proper criteria, it is important to take into consideration according to the characteristics of the gamma probe clarified in the present study.

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Background and Objectives : Lymph node metastasis is known as a significant predictor of prognosis in colorectal cancer patients. Recently, reverse transcriptase-polymerase chain reaction (RT-PCR) has been applied to detecting micrometastasis. To assess the risk of recurrence and cumulative disease-free survival (DFS), we examined lymph node micrometastasis in a series of colorectal cancer patients.
Methods : A total of 919 lymph nodes obtained from 65 colorectal cancer patients in the past 5 years starting from 1996 were examined using cDNA primers specific for carcinoembryonic antigen (CEA) and cytokeratin 20 (CK20), and were detected tumor cells by the RT-PCR analysis. Subsequently, the cumulative DFS rates were compared between histopathological (pN) and genetic (gN) metastases in the regional lymph node according to UICC TNM classification.
Results : (1) Ninety-five out of 512 histopathologically tumor-free lymph nodes, pN (-) showed positive expression for CEA and CK-20 (gN (+), 18.6%), and 23 out of 39 pN (-) patients showed positive mRNA expression. (2) All the patients showing gN (-) out of pN (-) could survive without any signs of recurrence (3) DFS showed a positive correlation with the increase in pN and gN stages. (4) Even in the pN (-) group, the gN2 patients showed poor prognosis compared with the gN1 or gN0 patients. (5) Among the combinations of pN and gN groups, the DSF rate was significantly higher in groups in the order gN (-) pN (-), gN (+) pN (-), gN (+) pN1 and gN2pN2 (p=0.0010).
Conclusions : Even in histopathologically negative lymph nodes, there is a considerable possibility of micrometastasis. Molecular detection of both CEA and CK-20 mRNAs in regional lymph nodes may introduce better prognostic values for patients with colorectal carcinoma. Patients showing gN (+) and pN1 might require some kind of postoperative adjuvant therapy.

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