Comparative study of Tc-99m MIBI and Tl-201SPECT in predicting chemotherapeutic response in non-small-cell lung cancer

Purpose: Tc-99m MIBI can be excluded from cytosol against its concentration gradient as a suitable transport substrate by P-glycoprotein. Tc-99m MIBI has also been shown to be more effective than TI-201 chloride for evaluatin g the response to chemotherapy in patients with small-cell lung cancer. The relation between Tc-99m MIBI accumulation by the tumor and its response to chemotherapy were evaluated in patients with nonsmall-cell lung cancer (NS CLC) and compared with the same parameters achieved using TI-201 chloride. Methods: Thirty-eight patients with NSCLC were examined before chemotherapy was begun. They were classified according to the results of a follow-up co mputed tomogram into two groups: responders were patients in whom there was a greater than or equal to 50% decrease and nonresponders were patients in whom there was a <50% decrease in the sum of the product of the maximum pe rpendicular diameters of all measurable lesions. All patients underwent dua l-isotope imaging with TI-201 chloride and Tc-99m MIBI just before chemothe rapy. Regions of interest were placed over the tumor uptake (T) and contral ateral normal lung tissue (N) areas on one coronal view with a clearly defi ned lesion, and the T:N ratio and retention index were calculated. Results: The delayed T:N ratio and retention index for Tc-99m MIBI in the r esponder group were significantly greater (P < 0.05) than those in the nonr esponder group. There was no significant correlation between the T:N ratio and retention index and tumor response using TI-201 chloride. Conclusion: Tc-99m MIBI SPECT may be more effective than TI-201 chloride SP ECT for evaluating the response to chemotherapy in patients with NSCLC.