, based on data from more than 3,000 individuals.
Pulmonary complications are now the most common causes of death in adults with systemic sclerosis (SSc), but the impact of patient characteristics and risk factors such as interstitial lung disease (ILD) and pulmonary hypertension (PH) on SSc outcomes remains unclear, wrote Pia Moinzadeh, MD, of University Hospital Cologne (Germany) and colleagues.
Although the role of ILD and PH in different SSc subtypes has been studied, larger studies of the effects of ILD and combining ILD and PH on outcomes are needed, since survival rates can change over time with new classification criteria, diagnostic tools, and improved therapies, they said.
In a study published in the journal Chest, the researchers reviewed data from 3,257 adults aged 18 years and older with SSc over a mean follow-up of 3.45 years. Participants were part of the German Network for Systemic Sclerosis (DNSS) that included 25 clinical centers in Germany. The participants were divided into SSc subsets: 54.2% with limited cutaneous SSc (lcSSc), 31.4% with diffuse cutaneous SSc (dcSSc), and 14.4% SSc overlapping syndromes.
The baseline prevalence of ILD was 34.5%, including 200 patients with ILD-PH and 923 with ILD but without PH. The baseline prevalence of PH without ILD was 4.5%. ILD was defined as SSc associated when other causes were excluded. PH was defined as an increase in mean arterial pressure of at least 25 mm Hg at rest, and also was defined by an estimated right ventricular systolic pressure greater than 35 mm Hg based on echocardiography.
By the end of the study period, 47.6% of SSc patients had ILD, 15.2% had ILD-PH, and 6.5% had pulmonary arterial hypertension (PAH). Of the SSc patients with ILD, 57.3% had dcSSc; the prevalence of PAH was not significantly different between the SSc subtypes. Patients with dcSSc were more likely to develop ILD-PH (52.2%) and ILD without PH (52.1%); patients with lcSSc were more likely to have PAH (64.9%) or no pulmonary involvement (64.1%).
“For all subsets, a significant increase in the frequency of SSc-ILD was observed during follow-ups,” the researchers noted.
Overall survival at 5 years was worst for patients with both ILD and PH (79.1%). Five-year OS for patients with PAH was 85.0%. OS at 5 years was significantly better for patients with ILD without PH (92.8%) and those with no pulmonary involvement (96.4%), compared with the ILD and PH patients (P < 0.001).
In a multivariate analysis, the risk of death was more than five times higher for patients with ILD-PH, compared with the reference group of patients without pulmonary involvement (hazard ratio, 5.3). Factors associated with reduced risk of death included female sex (HR, 0.3), higher body mass index (HR, 0.9), and higher diffusing capacity of the lung for carbon monoxide (HR, 0.98).
The findings were limited by several factors including the incomplete data for patients enrolled early in the registry, lack of complete radiology data, and the inability to determine whether the association between pulmonary involvement and survival was related to ILD or to pulmonary vascular disease, the researchers noted.
However, the results suggest that a combination of ILD and PH is the main predictor of death in patients with SSc and ILD, although the overall survival for SSc patients with and without pulmonary involvement has improved in recent decades thanks to improved therapies, multidisciplinary care, and greater attention to the disease worldwide, they concluded.
The study received no outside funding. Dr. Moinzadeh disclosed lecture fees from Boehringer Ingelheim.