Considerable differences in features of pulmonary hypertension among people with systemic sclerosis (SSc) markedly affect their survival chances, and treatment approaches given should be tailored accordingly, according to an analysis of patients grouped according to lung disease severity.
SSc patients with pulmonary hypertension (PH) but no evidence — or limited evidence — of interstitial lung disease were seen to have better survival chances at three years, its researchers reported.
The study, “Clinical phenotypes and survival of pre-capillary pulmonary hypertension in systemic sclerosis,” was published in the journal PLOS|ONE.
Pre-capillary PH can either arise idiopathically — unknown causes — or as the result of different causes, including connective tissue disease such as SSc. In fact, 10 percent of SSc patients develop this type of PH, and it remains a leading cause of mortality.
Their poor prognosis may be linked to the heterogeneity — diversity — of SSc. Since PH can have different causes and each requires a specialized therapy approach, it is important to identify the underlying cause of PH.
To identify and group patients accordingly, a team of researchers performed a so-called cluster analysis of two cohorts of SSc patients with pre-capillary PH, one in the U.S. and another in France.
“Cluster analysis can identify relevant clinical features to be used in personalized management strategies as well as to understand the relationships between clinical features and outcome variables,” the study notes.
Medical records of 200 SSc patients (124 in the French group and 76 in the U.S. group) were analyzed, and the researchers chose parameters related both to interstitial lung disease (ILD) — marked by progressive scarring of lung tissue — and PH severity, the two most critical factors linked with PH heterogeneity in SSc patients. The scarring associated with interstitial lung disease increasingly affects a person’s ability to breathe and supply enough oxygen to the bloodstream.
Clustering analysis identified four patient subgroups based on clinical features, and assessed three-year survival outcomes in each of the four clusters.
Cluster 1 had 94 patients, those with pre-capillary PH but limited or no evidence of ILD. These patients had a low diffusing capacity for carbon monoxide (DLCO) values, which measure the ability of the lungs to transfer gas from inhaled air to red blood cells of pulmonary capillaries, and is indicative of impaired lung function.
But they also had a mean forced vital capacity (FVC) — another measure of lung health; it’s the amount of air that can be forcibly and quickly exhaled — that was normal. Of the 94 patients in cluster 1, 81.5% survived for at least three years.
Cluster 2 patients also had pre-capillary PH, but mainly caused by extensive ILD and again associated with low DLCO values. These people were younger on average, but only 49.9% of them were seen to survive for three years or more.
Cluster C3 included 16 patients with severe pulmonary arterial hypertension, which is very high blood pressure in lung arteries causing narrowing or blockage of lung capillaries. No extensive ILD was found in group, but DLCO values were low. The three-year survival rate of this cluster was 61.9%.
Cluster 4 included 29 patients less severe pre-capillary PH, without extensive ILD, and with normal DLCO values. Their three-year survival rate, not surprisingly, was 87% — the best of these four clusters.
The three-year survival difference among clusters, after adjusting for patient age and sex, found that compared to cluster 1 (the reference group) those in cluster 2 had a significantly worse prognosis, with a trend toward worse outcomes in patients in cluster 3.
Researchers proposed that their work be given clinical relevance, with treatment approaches tailored to the specific clusters they identified — and lung transplants a possibility for those in clusters 2 and 3.
“Four homogeneous groups were identified. Two carried a dismal prognosis, one characterized by the presence of extensive ILD and another by severely impaired hemodynamics. It is probable that these two clusters would benefit from future efforts to improve their management, including early referral to lung transplantation centers,” they wrote.
“Our attempt to clarify the heterogeneity of this disease should help clinicians to anticipate the prognosis of patients and guide individual management,” the study concluded.