This study evaluates the midterm follow-up of tumor and normal tissue uptake of deoxyglucose, thymidine and methionine alter 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 ease 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.
|Number of pages||8|
|Journal||Journal of Nuclear Medicine|
|Publication status||Published - 1997 Feb 1|
- fractionated radiotherapy
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging