Immunosuppressive Drugs in Early Systemic Sclerosis and Prevention of Damage Accrual

OBJECTIVE: Organ damage in patients with systemic sclerosis (SSc) in individual organs such as the lungs may be prevented by receiving immunosuppressive drugs (ISs). A new measure of global organ damage, the Scleroderma Clinical Trials Consortium Damage Index (SCTC-DI), has allowed us to investigate whether receiving ISs may reduce global organ damage accrual in patients with early SSc. METHODS: This was a retrospective study of patients with two or less years of disease duration in Canadian and Australian cohorts with SSc. Patients with either limited cutaneous SSc (lcSSc) or diffuse cutaneous SSc (dcSSc) were observed separately and divided into groups who were either ever or never exposed to ISs. The SCTC-DI was the outcome, and inverse probability of treatment weighting (IPTW) was used to balance the study groups and to fit a marginal structural generalized estimating equation model. RESULTS: In the cohort with lcSSc, there were 210 patients, of whom 34% were exposed to ISs at some time. Exposure to ISs was associated with lower damage scores. In the cohort with dcSSc, there were 192 patients, of whom 76% were exposed to ISs at some time. Exposure to ISs was not associated with damage scores. CONCLUSION: In this retrospective observational cohort study, using IPTW to adjust for confounders, we found a protective effect of receiving ISs on damage accrual in patients with lcSSc. We were unable to determine such an effect in patients with dcSSc, but unknown confounders may have been present, and prospective studies of patients with dcSSc receiving ISs should include the SCTC-DI to determine the possible effect of ISs on damage accrual.