Expression of Permeability-glycoprotein (P-gp) and Uptake of Technetium-99m-Hexakis-2-Methoxy-Isobutyl-Isonitrile (Tc-99m-MIBI) in Malignant Tumor of the Head and Neck

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(Clinical evaluation) As for the retention index (delayed uptake / early uptake), 99m-Tc-MIBI showed the retention index of under 1 (mean ± SD = 0.853 ± 0.067) in malignant tumor, indicating a tendency of decreasing in the delayed uptake. On the other hand, the retention indexes of 201-TlCl scintigraphy were classified into three groups according to histopathological types of tumor ; 0.81 ± 0.06 in benign tumors, 1.01 ± 0.10 in well differentiated malignant tumors, 1.09 ± 0.13 in moderately differentiated tumors, and 1.24 ± 0.14 in poorly differentiated tumors. Thus, the mean retention indexes were under 1 in benign tumor, but over 1 in malignant tumor. The higher the histopathological grade was, the larger the retention index became.(Accumulation mechanism) As for the relationship between P-gp expression (score 0, 1 and 2) and histopathological type of tumor, the scores (mean ± SD) = 0.75 ± 0.19 in benign tumors, 0.71 ± 0.36 in well differentiated tumor, 0.83 ± 0.40 in moderately differentiated tumor, and 1.60 ± 0.24 in poorly differentiated tumor. Thus, the mean score of P-gp expression was small in the benign or low-grade malignant tumor, but large in the high-grade malignant tumors. Comparing of Na, K-ATPase expression (score 0, 1 and 2) to the histopathological type of tumor, the scores (mean) = 0.82 in well differentiated tumor, 1.44 in moderately differentiated tumor, and 1.50 in poorly differentiated tumors respectively.(Conclusion) 99m-Tc-MIBI and 201-TlCl scintigraphy showed different tendency of delayed uptake, and accurate diagnosis of tumor could be obtained by using both 99m-Tc-MIBI and 201-TlCl scintigraphy. P-gp and Na, K-ATPase expression were observed in accordance with the results of 99m-Tc-MIBI and 201-TlCl scintigraphy.