UNLABELLED: This study evaluates the midterm follow-up of tumor and normal tissue uptake of deoxyglucose, thymidine and methionine after fractionated radiotherapy to assess cancer recurrence in residual tumors. METHODS: AH109A tumor-burdened rats were treated with one to eight doses of 5Gy 60Co radiation. Tissue distribution study with 18F-FDG, 3H-thymidine and 14C-methionine, double-tracer autoradiography with 18F-FDG and 14C-methionine, and single-tracer autoradiography with 14C-labeled deoxyglucose, thymidine and methionine were performed 6 days after the end of therapy. RESULTS: Dose response study shows a significant decrease of tumor uptake of all tracers after two and more doses, even in the case of later recurrence. Whereas 3H-Thd and 14C-Met tumor uptake was similar to that of normal muscle, 18F-FDG tumor uptake remains higher than that of muscle, even in the case of complete tumor cure. The irradiated muscle shows a higher 18F-FDG uptake than the nonirradiated muscle. Autoradiography after eight doses (100% tumor cure) reveals elevated 14C-DG tumor uptake to be ascribable to nonmalignant cellular elements, in particular to a macrophage layer at the rim of necrotic areas. Autoradiography after four and six doses (33% and 57% tumor cure) shows the highest methionine and thymidine uptake in viable cancer cells, whereas deoxyglucose uptake did not differ between viable cancer cells and macrophages. CONCLUSION: To detect and differentiate viable cancer cells in a residual tumor mass after radiotherapy, PET using 11C-methionine or 11C-thymidine may have some advantages over 18F-FDG, especially if the residual tumor includes larger areas of necrosis.
UNLABELLED: This study evaluates the midterm follow-up of tumor and normal tissue uptake of deoxyglucose, thymidine and methionine after fractionated radiotherapy to assess cancer recurrence in residual tumors. METHODS: AH109A tumor-burdened rats were treated with one to eight doses of 5Gy 60Co radiation. Tissue distribution study with 18F-FDG, 3H-thymidine and 14C-methionine, double-tracer autoradiography with 18F-FDG and 14C-methionine, and single-tracer autoradiography with 14C-labeled deoxyglucose, thymidine and methionine were performed 6 days after the end of therapy. RESULTS: Dose response study shows a significant decrease of tumor uptake of all tracers after two and more doses, even in the case of later recurrence. Whereas 3H-Thd and 14C-Met tumor uptake was similar to that of normal muscle, 18F-FDGtumor uptake remains higher than that of muscle, even in the case of complete tumor cure. The irradiated muscle shows a higher 18F-FDG uptake than the nonirradiated muscle. Autoradiography after eight doses (100% tumor cure) reveals elevated 14C-DG tumor uptake to be ascribable to nonmalignant cellular elements, in particular to a macrophage layer at the rim of necrotic areas. Autoradiography after four and six doses (33% and 57% tumor cure) shows the highest methionine and thymidine uptake in viable cancer cells, whereas deoxyglucose uptake did not differ between viable cancer cells and macrophages. CONCLUSION: To detect and differentiate viable cancer cells in a residual tumor mass after radiotherapy, PET using 11C-methionine or 11C-thymidine may have some advantages over 18F-FDG, especially if the residual tumor includes larger areas of necrosis.
Authors: Y Waerzeggers; R T Ullrich; P Monfared; T Viel; M Weckesser; W Stummer; O Schober; A Winkeler; A H Jacobs Journal: Br J Radiol Date: 2011-12 Impact factor: 3.039
Authors: Norbert Galldiks; Roland Ullrich; Michael Schroeter; Gereon R Fink; Andreas H Jacobs; Lutz W Kracht Journal: Eur J Nucl Med Mol Imaging Date: 2010-01 Impact factor: 9.236