Systemic sclerosis is associated with an increased risk of cancer.

Systemic sclerosis is a diffuse connective tissue disease affecting skin, lungs, gastrointestinal tract and other visceral organs. Case reports and small case collections describe an apparent increase in the incidence of malignancy among systemic sclerosis patients. We addressed this issue with the first population based studies of cancer rates in systemic sclerosis patients using data from the Swedish cancer registry. : All patients carrying a discharge diagnosis of systemic sclerosis were identified from the Swedish impatient discharge registry. Using record linkage analysis with the Swedish National Cancer Registry, standardized incidence ratios (SIRʹs) were calculated for specific cancer sites. : A pilot study using data from the Uppsala region identified 233 patients with systemic sclerosis. The SIR for all cancers in the Uppsala cohort with systemic sclerosis was 2.4 (95% CI 1.5-3.6), with increased SIRʹs for lung cancer (7.8, 95% CI 2.5-18.2) and non-Hodgkinʹs lymphoma(9.6, 95% CI 1.1-34.5). Using discharge data for the entire country, we identified 917 patients with systemic sclerosis and 102 with localized scleroderma. The SIR for all cancers in the systemic sclerosis cohort was 1.5 (95% CI 1.2-1.9). The SIR for lung cancer was the highest (SIR 4.9, 95% CI 2.8-8.1), followed by non-melanoma skin cancer (SIR 4.2, 95% CI 1.4-9.8) and primary liver cancer (SIR 3.3, 95% CI 1.1-7.6). A suggestive increase in hematologic malignancies, specifically lymphomas, was also noted. Patients with localized scleroderma showed no increased risk of malignancy. : These studies confirm earlier reports of an association between systemic sclerosis and an increased risk for cancer. Specific tumor sites correspond to the sites commonly affected by fibrosis such as the lung and skin. These findings have implications for the pathogenesis of systemic sclerosis, and should encourage clinicians who care for systemic sclerosis patients to watch closely for signs of malignancy.