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

Abstract

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.

Keywords: Calcinosis cutis; Imaging; Positron Emission Tomography; Sodium Fluoride; Systemic sclerosis.