Tc-Sestamibi Scintigraphy in Suggesting the Therapeutic Effect of Chemotherapy against Gastric Cancer

Purpose: Imaging with Tc-sestamibi (Tc-MIBI) has been used to assess 170-kDa P-glycoprotein (P-gp) expression and predict chemotherapy responses in several types of malignancy, such as breast and lung cancers. The purpose of this study was to evaluate the relationship between Tc-MIBI accumulation in tumors and sensitivity to chemotherapy in gastric cancer patients. Experimental Design: Thirty-six patients with advanced gastric cancer underwent Tc-MIBI scintigraphy before chemotherapy. Patients also underwent endoscopic biopsy, and the expression of P-gp or multidrug resistance-associated protein was analyzed by immunohistochemical staining. The relationship between the accumulation of TcMIBI in tumors and responses to chemotherapy with 5-fluorouracil/cis-diamminedichloroplatinum(II) or epirubicin was examined. Results: Higher accumulation of Tc-MIBI in tumors was observed in 25 and 23 of 36 gastric cancer patients at the early (30 min) and delayed (120 min) images, respectively. Accelerated accumulation of TcMIBI negatively correlates with increased expression of P-gp, but not of multidrug resistance-associated protein, as determined by immunohistochemistry in gastric cancer tissues. The response rate to 5-fluorouracil/cis-diamminedichloroplatinum(II) chemotherapy in patients with high Tc-MIBI accumulation (15.4%) was much lower than that in patients with low Tc-MIBI accumulation (54.5%). In contrast, patients with high Tc-MIBI accumulation show a higher response rate (41.7%) to chemotherapy with epirubicin, which is known to be a substrate of P-gp transporter. Conclusions: Tc-MIBI scintigraphy is useful to suggest the responses to chemotherapy of patients with advanced gastric cancer.