To quantify the burden of cancer in systemic sclerosis (SSc).
Standardized incidence ratios (SIR) and mortality ratios (SMR) relative to the general Australian population were derived. Cox proportional hazards regression was used to estimate survival in SSc patients with cancer compared to those without. Determinants of cancer were identified using logistic regression. Healthcare cost was quantified through cross‐jurisicational data linkage.
This SSc cohort of 1,727 had cancer incidence of 1.3% per annum and prevalence of 14.2%, with SIR of 2.15 (93%CI 1.84‐2.49). The most common cancers were breast, melanoma, hematological and lung. RNAP III antibody was associated with increased risk of cancer (OR 2.9. p=0.044), diagnosed within five years of SSc disease onset. Calcium channel blockers were associated with a higher risk of overall cancer (OR 1.47,p=0.016), breast cancer (OR 1.61, p=0.051) and melanoma (OR 2.01, p=0.042). Interstitial lung disease (ILD) was associated with lung cancer (OR 2.83, p=0.031). Incident SSc cancer patients had more than a two‐fold increased mortality compared to SSc patients without cancer [HR 2.85 (95%CI 1.51‐5.37), p=0.001). SSc cancer patients utilized more healthcare than those without cancer with an excess annual healthcare cost of AUD$1,496 (p<0.001).
SSc carries an increased risk of developing cancer, particularly lung cancer associated with ILD, and breast cancer and melanoma occurring close to SSc disease onset in association with RNAP III antibodies. Compared to those without cancer, SSc cancer patients had higher mortality and increased healthcare cost with an annual excess per patient cost of AUD$1,496 (p<0.001).