Assessment of cancer recurrence in residual tumors after fractionated radiotherapy: a comparison of fluorodeoxyglucose, L-methionine and thymidine

J Nucl Med. 1997 Feb;38(2):280-7.

Abstract

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autoradiography
  • Carbon Radioisotopes / pharmacokinetics
  • Deoxyglucose / analogs & derivatives
  • Deoxyglucose / pharmacokinetics
  • Dose-Response Relationship, Radiation*
  • Fluorine Radioisotopes / pharmacokinetics
  • Fluorodeoxyglucose F18
  • Male
  • Methionine / pharmacokinetics
  • Neoplasm, Residual / diagnostic imaging*
  • Neoplasm, Residual / pathology
  • Neoplasms, Experimental / diagnostic imaging
  • Neoplasms, Experimental / radiotherapy*
  • Radiopharmaceuticals* / pharmacokinetics
  • Rats
  • Thymidine / pharmacokinetics
  • Tomography, Emission-Computed
  • Tritium / pharmacokinetics

Substances

  • Carbon Radioisotopes
  • Fluorine Radioisotopes
  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18
  • Tritium
  • Deoxyglucose
  • Methionine
  • Thymidine