Cancer Incidence in Rheumatic Diseases: Head-to-Head Comparison.

Background/Purpose: Rheumatic diseases (RD) are associated with increased risk of developing cancer. However, it remains to define, if particular cancers are more frequent in certain rheumatic diseases. To address this, the incidence and site of cancer were analyzed in a large cohort of patients with rheumatoid arthritis (RA), dermatomyositis/polymyositis (DM/PM), systemic sclerosis (SSc), systemic lupus erythematosus (SLE) and ankylosing spondylitis (AS).

Methods: All patients with a confirmed diagnosis of a RA, AS, SLE, DM/PM, and SSc who underwent clinical care in our institution between January 2000 and April 2012 were enrolled in this retrospective study. Data on site, staging, treatment, and outcome of cancer were ascertained per chart review. The cancer incidence rates in RDs were compared with those of the National Cancer Registry and standardized incidence ratios (SIR) were calculated.

Results: A total of 4,726 patients with RD (female, 71.0 %) were analyzed. During the follow-up duration of 34,447 person-years (PY), 244 (female, 71.7 %) patients developed cancer with an overall incidence rate of 5.2%. The SIR of cancer was significantly higher at 1.7 in patients with RD (95 % confidence interval (CI), 1.51-1.90) than the general population. In a subgroup analysis, RA (SIR 1.81, 95 % CI, 1.52-2.14), DM/PM (SIR 3.11, 95 % CI, 2.21-4.16), and SLE (SIR 1.65, 95 % CI, 1.29-2.04) were associated with a higher cancer incidence, whereas SSc (SIR 1.43, 95 % CI, 0.94-2.01) and AS (SIR 1.11, 95 % CI, 0.512-1.39) were not (Table 1). In RA, breast cancer was most common with 29 (22.0 %) cases, followed by 26 (19.7 %) gastric, 24 (18.2 %) lung,and 14 (10.6 %) colon cancer. In DM/PM, lung cancer was most common with 7 (17.9 %) cases, followed by 5 (12.8 %) colon, 4 (10.3 %) gastric and 3(7.7 %) breast cancer. In SSc, lung cancer was most common with 10 (35.7 %) cases, followed by 3 (10.7 %) gastric, 2 (7.1 %) cervix, and 2 (7.1 %) colon cancer. In SLE, thyroid cancer was most common with 12 (16.2 %) cases, followed by 7 (9.5 %) breast, 7 (9.5 %) cervix, and 7 (9.5 %) liver and intrahepatic bile ducts cancer. In AS, liver cancer was common with 3 (17.9%) cases, followed by 2(12.5%) lymphoid leukemia, and 2(12.5%) thyroid cancer.

Conclusion: To the best of our knowledge, this is the first study to show different malignancy risks among rheumatologic diseases in a head-to-head comparison. As particular cancer types are more frequent in certain rheumatic diseases, patients might benefit from cancer surveillance tailored to their RD.

Table 1. Standardized incidence ratios (SIRs) and 95 % confidence interval (CIs) of cancer in rheumatic diseases.