A pilot study treatment of malignant tumors using low-dose ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG)

Photons, electrons and protons have therapeutic use however positrons have only been used for diagnostic imaging purposes. The energies of positrons (β⁺) from F-18 (0.633 MeV) and electrons (β^-) from I-131 (0.606 MeV) are very close and have similar equilibrium dose constants. Since [¹⁸F]-fluorodeoxyglucose (¹⁸F-FDG) clears rapidly from circulation, administration of 37-74 GBq (1-2 Ci) of ¹⁸F-FDG is relatively safe from an internal radiation dosimetry point of view. We initiated a phase I dose escalation study to assess the safety, toxicity, and potential therapeutic utility of administering 100-200 mCi/m^{2 18}F-FDG delivered over a 1 to 5 day period in patients with advanced lymphomas and solid tumors refractory to standard of care treatment (SCT). Here we report the results of the first four patients treated. Four patients with advanced cancers received a single dose of 3.7-7.4 GBq/m² (100-200 mCi/m²) ¹⁸F-FDG. We monitored the patients for adverse effects and for response. No treatment-related toxicities were observed. There was no increased radiation exposure to personnel. Two patients showed decrease in the index lesions' SUVs by 17-33% (Day 1) and 25-31% (Day 30) post treatment. The two other patients showed stable disease on ¹⁸F-PET-CT. Interestingly, responses were seen at low radiotherapy doses (below 1 Gy). This exploratory study demonstrated the safety of therapeutic administration of up to 14.2 GBq (385 mCi) ¹⁸F-FDG. In patients with ¹⁸F-FDG-avid cancers, targeted radionuclide ¹⁸F-FDG therapy appears safe and may offer clinical benefit.