F-18-fluoride PET for monitoring therapeutic response in Paget's disease of bone

A prospective study was undertaken to evaluate PET with F-18-fluoride for monitoring the response to bisphosphonates in Paget's disease of bones. Methods: Fourteen patients with a monostotic (n = 9) or a polyostotic form (n = 5) of Paget's disease were scanned at baseline and at 1 and 6 mo after the beginning of treatment. Dynamic acquisition and arterial blood sampling were used to calculate the influx constant Ki (by both the Patlak [Ki-PAT] method and the nonlinear regression [Ki-NLR] method). Kinetic modeling was compared with maximal standardized uptake values (SUVmax) and biochemical markers of bone remodeling. Results: Baseline uptake of 18F-fluoride by pagetic bones was significantly higher than in normal bones (P < 0.05). One month after the start of treatment, SUVmax, Ki-PAT, Ki-NLR, and K-1 (the unidirectional clearance of fluoride from plasma to the whole of the bone tissue) decreased significantly by 27.8%, 27.9%, 27.5%, and 23.6%, respectively. Biochemical markers were already normalized in 6 of 9 patients with monostotic disease, although all had high F-18-fluoride uptake values. Six months after the start of treatment, F-18-fluoride uptake further diminished by 22.3%-25.6%. Biochemical markers were normal in all but 2 patients, although 10 of 14 patients still showed high F-18-fluoride uptake. One patient did not respond to treatment and maintained high uptake of F-18-fluoride throughout the study. SUVmax correlated with both Ki-PAT and Ki-NLR at baseline, 1 mo, and 6 mo (P < 0.05). Moreover, the change of SUVmax between baseline and 1 mo, as well as between baseline and 6 mo, also correlated with the change of Ki-PAT and Ki-NLR (P < 0.05). Conclusion: Our results show that F-18-fluoride PET can be used to noninvasively and accurately monitor the efficacy of treatment with bisphosphonates in Paget's disease of bones. SUVmax correlates with Ki-PAT and Ki-NLR and, interestingly, varies in the same manner as kinetic indices. Therefore, the use of SUVmax could avoid the need for dynamic acquisition and arterial blood sampling and would facilitate the use of whole-body PET in a clinical setting