Risk assessment in high grade sarcoma patients during neoadjuvant chemotherapy using multiple tracer PET

20006 Background: Patients with high grade soft tissue sarcomas are treated with neoadjuvant chemotherapy. Sarcomas have biological features that may predict for poor outcome. Some of these features are tumor proliferation rate, level of tumor hypoxia, and upregulation of tumor drug resistance mechanisms. Methods: We have a group of specific PET imaging agents to quantify the level of activity of these tumor processes. Patients with soft tissue sarcomas receive [C-11]Thymidine (TdR) to assess cellular proliferation, [O-15] Water to quantify tumor blood flow and to serve as the input function for quantification of the other tracers, [C-11]Verapamil to assess drug resistance mechanism activity, and [F-18]Fluoromisonidazole) FMISO to quantify changes in tumor hypoxic volume in response to treatment. These studies are performed in a single PET imaging session prior to neoadjuvant chemotherapy, after the second of four cycles of therapy and in the week prior to resection. Results: An example of this complex study result, is demonstrated by a recent patient with a high grade soft tissue sarcoma. The tumor showed increased TdR uptake, a moderate hypoxic volume, and [C-11] verapamil uptake prior to initiation of neoadjuvant adriamycin based chemotherapy. After 2 cycles of therapy, there was a significant decrease in the maximum level and volume of TdR uptake and a large reduction in tumor hypoxic volume. Conclusions: These data would imply a high risk soft tissue sarcoma due the presence of increased cellular proliferation, a significant hypoxic volume and the absence of p-glycoprotein activity determined by the presence of [C-11]Verapamil uptake. However, early response is also suggested by the findings above. Patient outcome will be assessed and correlated with these tumor parameters to further understand what tumor biological risk factors can be quantified non-invasively and repeated throughout the clinical course in soft tissue sarcoma patients. Supported by NIH NCI PO1 42045–18 and S10 RR017229–01 [Table: see text] No significant financial relationships to disclose.