Multiagent PET for risk characterization in sarcoma

A major goal of molecular imaging in cancer is to evaluate patient tumors for risk of treatment resistance and poor outcome using biologically specific PET agents. This approach was investigated using a multiagent imaging protocol for which patients were imaged in a single session to minimize changes in tumor parameters caused by multiple-day and -setting observation differences. Methods: We present data from a pilot study in 10 soft-tissue sarcoma patients imaged with ¹¹C-thymidine for cellular proliferation, ¹⁸F- fluoromisonidazole (FMISO) for tissue hypoxia, and 11C-verapamil for P-glycoprotein activity, in comparison with ¹⁵O-water for blood flow and ¹¹C-CO₂ for metabolite analysis and ¹⁸F-FDG clinical scans. Several patients underwent repeated imaging after adriamycin-based chemotherapy. Results: Quantitative imaging results showed that tumor uptake parameters vary between patients and with respect to each other in individual patients, suggesting that each patient's tumor biologic profile is unique. Specific tumor characteristics such as variable cellular proliferation, hypoxic volume, and upregulated P-glycoprotein activity were identified. Conclusion: This study shows that multiagent PET is feasible and yields unique and potentially complementary biologic information on individual tumors.