Non-response to Antitnf treatment in psoriatic arthritis can be predicted by an objective automated measurement of fluorescence-signal intensities in fluorescence-optical imaging technique - the first interims analysis of the xplore-study
Background/Purpose: Psoriatic arthritis (PsA) is a chronic inflammatory disorder. AntiTNF-therapy is initiated after failure of NSAID and DMARD-treatment. Up to 30-40% of the patients are primary not responding adequately to the induced therapy. In daily practice, response is assessed by improvement of disease activity measured by clinical examination and using composite indices (ACR20 response or DAS28). Earliest after 3 months, a decision for response is made. Feasible and robust biomarkers for early prediction of therapeutic response are still missing. Methods: Fluorescence optical imaging technique (FOI) is used as method for detection of changes in vascularisation of the hands as inflammatory marker. ICG is injected as fluorescence colour agent, stimulated by light in a specific wave length and recorded by a specific camera in the device. Overall fluorescence-signals and their intensities are measured by an automated computer-based reading of the disease activity (DACT). In a prospective multicentre study, value of FOI in measurement of disease activity and sensitivity to change in newly treated PsA patients (n=80) with Etanercept is investigated (XPLORE-study). In this first interims analysis (n=13), early changes of DACT (baseline to week 4) are measured and correlated to the clinical response (achievement of at least low disease activity: DAS28 ² 3.2) after 12 weeks of treatment. Results: All of the patients (mean age 55 years, female:male 1:1, mean DAS28 4.6, mean PASI 5.6, mean SJC 6.4, mean TJC 12.9 (66/68 joint count) at baseline) who did not reach at least 45% improvement in fluorescence intensities after 4 weeks of treatment did not achieve the threshold of low disease activity (DAS28 ² 3.2) at week 12. The treatment regime of most of those patients was changed after week 12. Only one patient without the described improvement was qualified as responder by DAS28 change of -3.0. Conclusion: Preliminary data of the first interims analysis of the XPLORE study illustrate high sensitivity in patients newly treated with Etanercept-therapy. Achievement of improvement of at least 45% in fluorescence intensity shows already after 4 weeks a high discriminative value for prediction of later clinical response at week 12. Only one patient was qualified as responder although he did not meet the criteria for response in fluorescence signalling. In this case, disease activity seems to be driven by other factors than inflammatory arthritis (only 1 SJC/TJC at baseline). Early change in fluorescence signalling seems to be a promising marker for prediction of clinical response in newly initiated biological treatment.