COMMENT:
Although it is a frequent diagnosis, existing imaging techniques lack accuracy as they are limited to the detection of fibrosis in the tissue but are unable to identify changes in collagen degradation (fibrolysis) or deposition (fibrogenesis), both of which are essential in the assessment of treatment response.
This article exposes the effectiveness of different radiotracers in order to detect fibrosis progression.
KEY LEARNINGS:
Positron emission tomography (PET) has proven to be more accurate than positron emission tomography (SPECT) in measuring the progression and real-time activity of fibrosis. Multiple different markers exist for PET labelling, but limitations exist for each. αvβ3 and αvβ6 integrins can potentially be applied in PET tracers to expose fibrosis but the target cells of these integrins remain unknown. Conversely, pericyte marker PDGFRβ is an efficient fibrogenic marker, but a high-affinity PDGFRβ ligand has yet to be developed, although gallium-68-labelled affibody molecule scaffold is promising. FAP is another potential marker that shares the same issue as αvβ Integrin and gallium-68-labelled, as its expression does not provide clarity on either an increased fibrogenesis or fibrolysis, although it is present on fibrotic lesions. Molecular imaging targeting ECM proteins like collagen, using radioligands such as collagelin analogues and CBP8 in PET, offers potential for accurate fibrosis assessment, with ongoing clinical trials demonstrating safety and efficacy in detecting active collagen deposition in diseases like idiopathic pulmonary fibrosis.
