Lack of correlation of functional scintigraphy with (99m)technetium-methoxyisobutylisonitrile with histological necrosis following induction chemotherapy or measures of P-Glycoprotein expression in high-grade osteosarcoma

In osteosarcoma, some studies have suggested P-glycoprotein expression Is a prognostic factor. The clearance of (99m)technetium hexakis-2-methoxyisobu tylisonitrile (Tc-99m-MIBI) has been used in some tumor systems as an in vi vo measure of P-glycoprotein-mediated efflux. In this study we explored the correlation between Tc-99m-MIBI clearance and histological necrosis follow ing induction chemotherapy and P-glycoprotein expression in osteosarconia. The primary tumors of 20 patients with high-grade osteosarcoma were imaged at diagnosis with Tc-99m-MIBI, and the uptake ratios and biological half-li ves were calculated. P-Glycoprotein expression in the tumor tissue was dete rmined immunohistochemically and by measuring mRNA expression of the multid rug resistance-1 gene. The histological necrosis following induction chemot herapy was assessed by the Huvos grading system. The biological half-life o f Tc-99m-MIBI ranged from 1.4 to 52.5 h. Seven of the 20 tumor samples had a favorable extent of necrosis following induction chemotherapy. The Tc-99m -MIBI half-life and uptake ratio showed no correlation with histological ne crosis following induction chemotherapy. The Te-99m-MIBI half-life and upta ke ratio did not correlate with either measure of P-glycoprotein expression . The results of this pilot study indicate that Tc-99m-MIBI imaging is not an effective predictor of histological necrosis following induction chemoth erapy in high-grade osteosarcoma. (99m)Mc-MIBI imaging did not correlate wi th measures of P-glycoprotein expression in the tumor tissue.