Aims: This is a retrospective and adaptive randomization study. The purpose of this study was to evaluate the relationship between technetium-99m methoxyisobutylisonitrile (Tc-99m MIBI) chest-imaging results, chemotherapy response and P-glycoprotein (Pgp) or multidrug resistance related protein (MRP) expression in small-cell lung cancer (SCLC). Patients and methods: Before chemotherapy, 30 patients (11 females, 19 males, ages: 52-69 years) with SCLC, including 14 extensive diseases without localized problems and 16 limited diseases in excess of solitary pulmonary nodule, underwent early chest imaging, including visual interpretation and quantitative analyses of tumor uptake ratio (TUR), 10 minutes after intravenous injection of Tc-99m MIBI. Immunohistochemical analyses were performed, using multiple nonconsecutive sections of the biopsy specimens, to detect Pgp and MRP expressions. Chemotherapy response was evaluated in the third month after completion of treatment by clinical and radiological methods. Results: All 15 (100%) of the SCLC patients with complete or partial response had positive Tc-99m MIBI chest SPECT results, but negative ones for both Pgp and MRP expression. Twelve of the 15 (80%) SCLC patients with no response or progressive disease had negative Tc-99m MIBI chest SPECT results and were positive for either Pgp or MRP expression (P <0.05). Negative Tc-99m MIBI chest SPECT results predicted complete or partial response. The TUR of patients with complete or partial response (1.91 ± 0.29 with a 95% confidence interval (95% CI): 1.75-2.07) was significantly higher than that of patients with no response or progressive disease (1.19 ± 0.28 with a 95% CI: 1.04-1.35). Conclusion: Tc-99m MIBI chest images are a potential tool for understanding Pgp and MRP expressions in SCLC and for predicting patient chemotherapy response.
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