[The German network for systemic sclerosis (DNSS): current data on diagnostics and therapy]

Prognostic value of cardiopulmonary exercise testing in patients with systemic sclerosis

Background

Systemic sclerosis (SSc) is a severe rheumatic disease of the interstitial tissue, in which heart and lung involvement can lead to disease-specific mortality. Our study tests the hypothesis that in addition to established prognostic factors, cardiopulmonary exercise testing (CPET) parameters, particularly peak oxygen uptake (peakVO₂) and ventilation/carbon dioxide (VE/VCO₂)-slope, can predict survival in patients with SSc.

Subjects and methods

We retrospectively assessed 210 patients (80.9% female) in 6 centres over 10 years with pulmonary testing and CPET. Survival was analysed with Cox regression analysis (adjusted for age and gender) by age, comorbidity (Charlson-Index), body weight, body-mass index, extensive interstitial lung disease, pulmonary artery pressure (measured by echocardiography and invasively), and haemodynamic, pulmonary and CPET parameters.

Results

Five- and ten-year survival of SSc patients was 93.8 and 86.9%, respectively. There was no difference in survival between patients with diffuse (dcSSc) and limited cutaneous manifestation (lcSSc; p = 0.3). Pulmonary and CPET parameters were significantly impaired. Prognosis was worst for patients with pulmonary hypertension (p = 0.007), 6-min walking distance < 413 m (p = 0.003), peakVO₂ < 15.6 mL∙kg^− 1∙min^− 1, and VE/VCO₂-slope > 35. Age (hazard ratio HR = 1.23; 95% confidence interval CI: 1.14;1.41), VE/VCO₂-slope (HR = 0.9; CI 0.82;0.98), diffusion capacity (Krogh factor, HR = 0.92; CI 0.86;0.98), forced vital capacity (FVC, HR = 0.91; CI 0.86;0.96), and peakVO₂ (HR = 0.87; CI 0.81;0.94) were significantly linked to survival in multivariate analyses (Harrell’s C = 0.95).

Summary

This is the first large study with SSc patients that demonstrates the prognostic value of peakVO₂ < 15.6 mL∙kg^− 1∙min^− 1 (< 64.5% of predicted peakVO₂) and VE/VCO₂-slope > 35.

Pharmacology and rationale for imatinib in the treatment of scleroderma

Systemic sclerosis (scleroderma) is a chronic, multisystem, fibrotic disease. Although the pathogenesis is not completely understood, early vascular damage leads to an inflammatory reaction and a severe fibrotic response. Therapy of systemic sclerosis is still not convincing and is mainly restricted to the management of organ complications. A wide choice of immunosuppressive and antifibrotic drugs has been used to try to modify the course of the disease, but significant breakthroughs are still lacking. Imatinib is a tyrosine kinase inhibitor known to regulate growth, proliferation, and differentiation as well as apoptosis of cells and is already widely used for several malignancies, eg, chronic myeloid leukemia and gastrointestinal stromal tumors. It has been used in preclinical as well as clinical studies to modulate the fibrotic process in patients with systemic sclerosis. This is based on its activity to interfere selectively with both the transforming growth factor-β and platelet-derived growth factor signaling pathway. Preclinical studies in mouse models of scleroderma showed significant anti-inflammatory and antifibrotic effects; however, several clinical, proof-of-concept trials have not yet confirmed these initially promising results.