Abstract
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Objectives Ga-68 NOTA bisphosphonate (GBN) is a generator produced PET radiopharmaceutical for skeletal imaging. This is a prospective dual tracer PET/CT study to compare GBN with F-18 Fluoride (NaF) for the detection of skeletal metastasis in breast cancer patients.
Methods 14 breast cancer patients (Age=44.9 ± 10.6 years) with newly diagnosed bone metastases on Tc-99m MDP scintigraphy were prospectively enrolled to undergo dual tracer PET/CT within one week. GBN dynamic PET was acquired in three patients to evaluate tracer kinetics in normal bone and metastases. The average activity administered for GBN was 136.3 ± 29.15 MBq and for NaF 154 ± 30.9 MBq. Imaging was started 30 minutes post-injection for both tracers on a Biograph mCT scanner (Siemens). Scans were independently evaluated by two expert nuclear physicians for site and number of lesions, SUVmax and corresponding CT changes. Kappa statistic for concordance between GBN and NaF was scored.
Results Plasma clearance half time for GBN was 6.4 minutes (median, range= 1.4 to 13.5 minutes) with SUVmax in normal bone of 4.2 ± 2.5. Peak uptake of GBN in the metastatic lesion was seen at 33 ± 4.5 minutes with SUVmax 16.7 ± 13.4. Image quality of GBN was comparable to NaF and both were completely concordant on a patient wise basis. On a lesion-wise basis 117 lesions were demonstrated on GBN and 125 on NaF. Weighted kappa for concordance between GBN and NaF on a lesion wise basis was 0.89 (95 % CI= 0.82 to 0.96, SE= 0.04).
Conclusions An excellent pharmacokinetics and lesion detection concordance between GBN PET/CT and NaF PET/CT suggests its potential as a generator based PET radiopharmaceutical for skeletal scintigraphy.