18F-Fluoride PET/CT and 99mTc-MDP SPECT/CT can detect bone cancer at early stage in rodents

Noninvasive imaging using positron emission tomography/computed tomography (PET/CT) and single photon emission computed tomography/computed tomography (SPECT/CT) are considered revolutionized approaches to detect bone cancer. Both PET/CT and SPECT/CT technologies have advanced to permit miniaturization, which has provided the advantage of including animals as their own controls in longitudinal studies. The present study was designed to evaluate the potential of PET/CT and SPECT/CT as research tools to detect bone cancer in rats. We used a rat model of bone cancer induced by injecting Walker 256 tumor cells into the femoral cavity. Computed tomography demonstrated that rats presented a solid tumor at 15 days post injection (dpi). However, CT was not an effective method for identifying tumors at an earlier time point (8 dpi), when mechanical hyperalgesia (the most common symptom during bone cancer progression) had already initiated. At this early stage, PET/CT and SPECT/CT analysis detected higher uptake in the injected femur of the tracers 18F-Fluoride and 99mTc-Methyl diphosphonate (99mTc-MDP), respectively. These findings demonstrated for the first time that both 18F-Fluoride PET/CT and 99mTc-MDP SPECT/CT can detect cancer at early stages in rats and advocates for the PET/SPECT/CT as research tools to evaluate bone cancer in further longitudinal studies involving small animals.