[18F]Sodium Fluoride PET has the potential to identify active formation of calcinosis cutis in limited cutaneous systemic sclerosis

OBJECTIVES: Calcinosis cutis affects 20-40% of patients with systemic sclerosis (SSc). When calcinosis cutis becomes clinically apparent, it is irreversible in most cases. Detection of active calcification formation might allow early disease-modifying interventions. We assessed the feasibility of visualizing active calcifications using [18F]Sodium Fluoride ([18F]NaF) PET/low-dose CT (LDCT) in SSc patients with calcinosis cutis.

METHODS: In this cross-sectional, observational pilot study patients underwent a whole body [18F]NaF PET/LDCT. All patients met the 2013 ACR/EULAR SSc criteria and had clinically detectable calcinosis cutis. (Sub)cutaneous calcifications were described by three investigators.

RESULTS: Nine female patients were included (median age 59.0 years [IQR 51.5-70.5]). [18F]NaF uptake was mostly visible in the fingers (n=7) and knees (n=5). [18F]NaF PET showed calcifications in the fingers of 3 patients where calcifications were undetected on LDCT and in the clinic. Ninety-seven percent of [18F]NaF positive lesions was visible on LDCT. Of all lesions visible on LDCT, 70% was also visible on [18F]NaF PET.

CONCLUSION: Imaging of active calcifications in SSc is feasible using [18F]NaF PET/LDCT. Seventy percent of calcifications on LDCT were [18F]NaF PET positive. Although these findings require replication, [18F]NaF PET/LDCT may detect active calcification formation, being potentially suitable for early disease-modifying interventions.