P113 Imaging neoangiogenesis in rheumatoid arthritis (INIRA): whole-body synovial uptake of a 99mTc-labelled RGD peptide is highly correlated with power Doppler ultrasound
Authors: Attipoe Laura , Garrood Toby , Opena Maria , Blanco-Gil Cristina , Subesinghe Sujith , Norton Sam , Rosser Mark , Cook Gary , Cope Andrew 
Published: April 2020

Abstract

Background
Power Doppler ultrasound (PDUS) is superior to clinical examination in detecting synovitis in patients with rheumatoid arthritis (RA). Although dynamic and cheap it is impractical to scan large numbers of joints in routine clinical settings. MRI, whilst sensitive for synovitis, is expensive and routine use is limited to targeted joints. Bone scintigraphy produces whole body images but due to lower specificity is not routinely used. 99mTc-maraciclatide (Serac Healthcare) is a radio-labelled tracer which binds with high affinity to integrin αvβ3 (αvβ3), a cell-adhesion molecule up-regulated on neoangiogenic blood vessels. It therefore has the potential to image synovial inflammation at the whole-body level. We previously showed in a pilot study that uptake was seen in the inflamed joints of 5 RA patients and that this correlated with PDUS. This study explores correlation with PDUS in a larger group of patients with varied disease activities.

Methods
50 patients with RA, fulfilling ACR 2010 classification criteria, were recruited. Patients underwent an ultrasound scan of 40 joints with grey scale (GS) and PD quantification. Each joint was scored on a scale of 0-3 for GS and PD with a total score calculated for each patient. Within 3 hours of the ultrasound, patients were injected with 740 MBq of 99mTc-maraciclatide. Using a gamma camera, whole body planar views and dedicated hand and foot views were taken 2 hours after injection. Acquisition time was 20 minutes for whole body, and 20 minutes for hand and foot views. 99mTc-maraciclatide images were scored as positive or negative uptake for each joint (binary score). A quantitative score was also calculated for each joint where there was uptake with this corrected for background muscle uptake. Total binary and quantitative scores per patient were calculated. Ultrasound and 99mTc-maraciclatide scores were tested for correlation with Pearson’s correlation coefficient (r) and the coefficient of determination (r2).

Results
Strong correlation was seen when total PDUS was compared to binary scores (r = 0.92, r2=0.85) and quantitative scores (r = 0.85, r2=0.72). p was &lt;0.0005 for all results. 99mTc-maraciclatide uptake was also seen in inflamed tendons/tendon sheaths. The imaging procedure was well-tolerated.

Conclusion
99mTc-maraciclatide uptake was highly correlated with PDUS highlighting its potential as an alternative imaging modality. 99mTc-based planar imaging has the unique capacity to image the whole body and hence the total synovial inflammatory load in a quick acquisition. The imaging equipment to perform these scans is already widely available in radiology departments. Interpretation of scans is also much simpler compared to US/MRI. It could therefore have a role in key decision-making points in pathways for diagnosis, treatment failure, and remission prior to dose tapering.

Disclosures
L. Attipoe None. T. Garrood Grants/research support; Serac Healthcare. M. Opena None. C. Blanco-Gil None. S. Subesinghe None. S. Norton None. M. Rosser Other; Serac Healthcare Ltd. G. Cook None. A. Cope Grants/research support; AP received funding for research from BMS.