Characterization of Spinal Pathology in Axial Psoriatic Arthritis

Abstract
Axial psoriatic arthritis (AxPsA), that is psoriatic arthritis (PsA) with involvement of the joints and ligaments of the
spine, is a sequel of chronic inflammation of the PsA disease process. The spectrum and nature of inflammation
in AxPsA is not fully understood, and therefore the condition is often misdiagnosed or underdiagnosed. Current
evidence suggests that axial entheseal soft-tissue-associated pathology is likely to be the dominant pathology
in AxPsA, compared to osteitis in ankylosing spondylitis (AS). These soft tissues involved in PsA spinal pathology
are relatively avascular structures compared with tissues such as the bone/synovium and are therefore a ‘blind
spot’ for current imaging technology. Positron emission tomography (PET), as a molecular imaging modality, has
potential to interrogate these tissues directly, however, it has not been exploited for this application, due to
concerns associated with dose, spatial resolution and scan time. Recently, total-body PET/CT technology has
been introduced that may address these concerns. Indeed, in our preliminary studies, we utilized this technology
and visualized and quantified spinal enthesitis as a dominant pathology in majority of the evaluated study
participants with PsA.
Based on these observations, our central hypothesis is that TB-PET/CT measures will (1) offer a unique insight
of the pathology of AxPsA in vivo, and (2) provide biomarkers that will associate with the total spinal inflammatory
burden in PsA. To test this hypothesis, our study has two proposed aims. Our first aim will characterize the
inflammatory pathologies underlying AxPsA in vivo. We will derive consolidated, whole-spine measures from TB-
PET/CT, as surrogate, in vivo measures of inflammatory pathology and establish their discriminatory power
against those derived from participants with AS. Our second aim will quantify the total spinal inflammatory load
in AxPsA via TB-PET/CT, and compare it with standardized outcome measures and MRI evaluation of spinal
pathology.
This study will assess the performance of TB-PE/CT to identify pathologies associated with spinal inflammation
in AxSpA, quantify the total spinal inflammatory load, and perform comparison of resulting metrics with those
derived from participants with AS. If successful, this study will contribute novel, objective and quantifiable TB-
PET/CT imaging metrics (biomarkers) of spinal inflammation in PsA. Data collected will provide robust sample
size estimates and feasibility measures for informing future clinical studies (observational and interventional
trials), using the proposed imaging measures as outcome or surrogate measures.

Grant Number: 1R01AR085314-01
NIH Institute/Center: NIH
Principal Investigator: Abhijit Chaudhari