in a population-linked cohort study published in Arthritis Care & Research.
Kathleen Morrisroe, MBBS, PhD, of St. Vincent’s Hospital Melbourne and colleagues matched deidentified patient data in the Australian Scleroderma Cohort Study (ASCS) with patients’ respective state cancer registry data between January 2008 and December 2015. The researchers also used the Australian Medical Benefit Schedule (MBS) to track health care costs for hospital admissions, presentations to the ED, other health visits, pathology, and imaging, as well as other associated costs for care, in each state. Based on this information, Dr. Morrisroe and colleagues calculated standardized incidence ratios (SIR) and standardized mortality ratios (SMR) for these patients by comparing them with the general population in Australia.
The results included 1,727 patients with systemic sclerosis (SSc) and cancer in the cohort, which consisted of mostly white (92.1%) women (85.9%) who had limited cutaneous SSc (73.9%). They were a mean of 46.6 years old when they were diagnosed with SSc and had a mean disease duration of 10.9 years. The incidence of cancer was 1.3% per year, and the overall prevalence for the cohort was 14.2%, which was higher than the general Australian population (SIR, 2.15; 95% confidence interval, 1.84-2.49). Breast cancer, melanoma, hematologic cancer, and lung cancer were the most common types of cancers found in the cohort, with early breast cancer (SIR, 3.07; 95% CI, 1.47-5.64), lung cancer (SIR, 3.07; 95% CI, 1.21-3.44), and early melanoma (SIR, 3.40; 95% CI, 1.10-7.93) having a higher incidence than the general population.
Patients with RNA polymerase III (RNAP) autoantibody had a higher incidence of early onset cancer (odds ratio, 2.9; P = .044), defined as a cancer diagnosis within 5 years of SSc diagnosis. Interstitial lung disease was also linked to an increased risk of lung cancer (OR, 2.83; P = .031), which persisted after the researchers performed a multivariate analysis.
Another factor that increased the overall risk of cancer was calcium channel blockers (OR, 1.47; P = .016), which also increased the risk of breast (OR, 1.61; P = .051) and melanoma-specific cancers (OR, 2.01; P = .042), a finding the researchers said was “unexpected, but has been reported in the literature with conflicting results.”
“This association is hypothesized to be related to the role of calcium in cell apoptosis, such as activation of the caspase pathway, induction of endonuclease activity and mitochondrial permeation,” Dr. Morrisroe and colleagues wrote.
SSc patients had more than a doubling of risk of mortality with incident cancer in comparison with SSc patients who did not have cancer (hazard ratio, 2.85; 95% CI, 1.51-5.37; P = .001). The average cost of health care annually for an SSc patient with cancer was AUD $1,496 (P less than .001), the researchers said.
This study was funded in part by Scleroderma Australia, Arthritis Australia, Actelion Australia, Bayer, CSL Biotherapies, GlaxoSmithKline Australia, and Pfizer. Dr. Morrisroe reported receiving support from Arthritis Australia and Royal Australasian College of Physicians Research Establishment Fellowships. Another author reported receiving a fellowship from the National Health and Medical Research Council of Australia. The other authors reported no relevant conflicts of interest.
SOURCE: Morrisroe K et al. Arthritis Care Res. 2019 Sep 20. doi: 10.1002/acr.24076