Early mortality in systemic sclerosis: Rationale for forming a multinational inception cohort of patients with scleroderma (the insync study).

Abstract

Aim: Systemic sclerosis (SSc) has substantial mortality. We hypothesise that survival rates from prevalent cohorts may underestimate mortality early in the disease course, particularly in patients with diffuse disease who may have died before having the opportunity to enter the cohort.We sought to compare 10-year survival and causes of death in an inception cohort with a prevalent cohort of Australian patients with SSc. Method(s): All patients enrolled in the Australian Scleroderma Cohort Study (ASCS) were included. Kaplan Meier curves were used to compare cumulative survival according to disease subtype, diffuse (dcSSc) v. limited (lcSSc) in (i) the cohort as a whole (ii) patients recruited within 5 years of disease onset the 'incident cohort'. The single primary cause of death was classified as either SSc-related or non-SSc related. SSc-related factors and other comorbidities that contributed to death were also recorded. Result(s): here were 1001 patients in the whole cohort, with 27 deaths (15 diffuse, 12 limited) over 8 years of follow-up.There were 333 patients in the incident cohort, with 25 deaths (15 diffuse, 9 limited) over 8 years follow-up from disease onset. In the prevalent cohort, the 10-year survival of patients with dcSSc was 90%, whereas it was only 70% in the incident cohort. Fifteen of 27 deaths (55.6%) in the first decade were SSc-related (7 PAH, 4 ILD and 4 PAH and ILD), while 12 (44.4%) were non-SSc-related (8 malignancy, 1 sepsis, 1 cerebrovascular disease, 2 'other'). Conclusion(s): There is substantial mortality early in the course of SSc, specifically in patients with dcSSc, which is quantifiable only in an inception cohort of patients who are recruited from disease onset and followed prospectively. This provides a compelling rationale for forming a large inception cohort of patients with SSc to evaluate prognosis and disease outcomes.