Local data from the Pulmonary Hypertension Society of Australian and New Zealand (PHSANZ) Registry confirms that Australian patients with PAH aren’t doing too badly considering limited access to combination therapy.
In a study of 220 cases of predominantly idiopathic PAH diagnosed between the beginning of 2012 and the end of 2016, one-year survival was 95.6%, two-year survival 87.3% and three-year survival 77%.
Co-author Dr Edmund Lau, from the University of Sydney and Royal Prince Alfred Hospital, said the findings compared favourably to patient survival rates from PAH registries in other Western countries.
For example, a French study from 2002-2003 reported a one-year survival of 83% and three-year survival of 58%.
“However their data comes from an earlier time than our population and treatment has evolved quite rapidly in this field over the past decade,” Dr Lau said.
The Australian study reported 74% of patients started treatment on monotherapy – typically an endothelin receptor antagonist – 24% on dual combination therapy and 2% on triple therapy
Dr Lau said the low rates of combination therapy were consistent with the time period before stronger evidence was available for the benefits of initial combination therapy.
“In 2017, by far the majority of patients would be started on combination therapy from the time of diagnosis,” he said.
While combination therapy for PAH is still not available on the PBS, patients who really need it were able to access it via compassionate access schemes or clinical trials.
“We’re probably also doing well because many patients are treated at specialist centres with a lot of experience in the management of PAH.”
The study found only male age and lower exercise capacity (6-minute walk distance) were predictors of worse survival in the study group while obesity was associated with improved survival.
Dr Lau said the ‘obesity paradox’ has been seen in other registries including re-analyses of very old data.
“As to the mechanism – why obesity is an independent predictor of better survival – none of us have any idea. It needs to be investigated.”