CHICAGO — Patients with ankylosing spondylitis had an increased risk for melanoma, hematological malignancies, kidney and thyroid cancer but a reduced risk for lung, esophagus, stomach, colorectal, liver and gallbladder cancer compared with the general population, according to data presented at the ACR/ARHP 2018 Annual Meeting.
Sara Alehashemi, MD, of the NIH’s National Institute of Arthritis and Musculoskeletal and Skin Diseases, said the findings are consistent with previous research demonstrating a protective effect of NSAIDs — the first-line treatment for AS — on gastrointestinal (GI) cancer and lung cancer incidence.
“Studies on cancer and NSAID exposure are heterogenous,” she said. “But overall, their GI cancer protective effect has been shown repeatedly in literature.”
In general, few studies have examined the incidence of cancer in patients with AS in the United States, according to Alehashemi. Those that do exist have a short follow-up period of approximately 5 years. An analysis of pooled data from these studies failed to show a significant association between AS and cancer.
To gather more data, Alehashemi and Michael Ward, MD, PhD, also of the National Institute of Arthritis and Musculoskeletal and Skin Diseases, conducted a retrospective study using Medicare databases from 1999 to 2015 to examine the risk for organ-specific cancers in a large cohort of patients with AS in the U.S. Their analysis included 13,305 Medicare beneficiaries with AS (66% men, 91% white) and more than 6 million unaffected controls (66% men, 85% white) who were matched by age and gender.
The researchers used standardized incidence ratios (SIRs) to define the proportion of observed or expected number of cancers in patients with AS compared to the reference group. The incidence rates accounted for person-years at risk.
Overall, 3,322 cases of cancer were identified in patients with AS and 1,211,126 cases were identified in matched controls. Compared with the general population, patients with AS had a greater risk for:
- kidney cancer (SIR = 1.57; 95% CI, 1.34-1.80);
- melanoma (SIR = 1.49; 95% CI, 1.27-1.71);
- thyroid cancer (SIR = 1.43; 95% CI, 1.02-1.85);
- leukemia (SIR = 1.44; 95% CI, 1.24-1.65);
- non-Hodgkin’s lymphoma (SIR = 1.36; 95% CI, 1.19-1.53); and
- prostate cancer (SIR = 1.34; 95% CI, 1.25-1.42).
Meanwhile, they had a lower risk for:
- esophagus cancer (SIR = 0.58; 95% CI, 0.36-0.81);
- stomach cancer (SIR = 0.55; 95% CI, 0.32-0.79);
- colorectal cancer (SIR = 0.81; 95% CI, 0.71-0.91); and
- lung cancer (SIR = 0.72; 95% CI, 0.64-0.81).
Alehashemi noted several limitations to the study, including the lack of medication information and the possibility of disease misclassification.
“Our next step is to identify other AS-related factors that are protective or considered to be a risk factor for cancer,” she said. – by Stephanie Viguers
Alehashemi S, et al. Abstract 895. Presented at: ACR/ARHP Annual Meeting, Oct. 20-24, 2018; Chicago.
Disclosure: Alehashemi repots no relevant financial disclosures.