Systemic sclerosis (SSc) is a rare autoimmune disease characterized by various degrees of skin fibrosis and internal organ involvement. Interstitial lung disease (ILD), or pulmonary fibrosis, is a common complication of SSc, affecting up to 50% of patients. Immunosuppressive drugs are currently used to treat SSc-ILD, particularly in patients with pulmonary symptoms (e.g. shortness of breath or cough), severe lung function impairment, or progressive worsening disease. However, the usefulness of these drugs in patients with normal or mildly impaired lung function is currently unclear, given that this patient population was mostly excluded from randomized controlled trials. Yet, SSc-ILD with normal or mildly impaired lung function is frequent, representing approximately half of all SSc-ILD patients.
In the course of her Masters of Epidemiology thesis project at McGill University, Dr. Hoa was interested in exploring the role of immunosuppressive drugs, namely cyclophosphamide and mycophenolate mofetil, in the treatment of patients with mild SSc-ILD. Using data collected in the Canadian Scleroderma Research Group (CSRG) registry from 2004 to 2017, she studied the characteristics and outcomes of 116 patients with mild SSc-ILD. About 10% of these patients were exposed to cyclophosphamide or mycophenolate mofetil mostly for joint and skin disease. After one year, the forced vital capacity (a measure of lung function) of patients who were exposed to these drugs was compared with that of patients who were not exposed to these drugs.