Background/Purpose: Patients with rheumatoid arthritis (RA) have a modest increased risk of overall cancer and of lymphoma. The purpose of our study was to report trends in the incidence of all site cancers and lymphoma in US Veterans with RA relative to US population-based rates from the Surveillance, Epidemiology, and End Results (SEER) Program.

Methods: In order to identify RA patients in the national VA, we used the following algorithm:  ≥2 RA diagnostic codes at least 30 days apart, rheumatologist diagnosis of RA, and either a DMARD prescription or positive autoantibody test (RF or anti-CCP) within the VA Corporate Data Warehouse between 1/2001-12/2015; exclusion criteria included patients with diagnostic codes for psoriatic arthritis or ankylosing spondylitis. Diagnoses of all site cancers (includes all cancers -in situ and malignant) were identified from the VA Central Cancer Registry (VACCR) and mortality data from the National Death Index.  The study period was divided into three 5-year intervals: 2001-2005, 2006-2010, and 2011-2015. Person-years of follow-up for RA patients was calculated from the index date (first fulfilling the RA algorithm) to the earliest of death, the development of any cancer (for trends in all site cancer), or development of lymphoma (for trends in lymphoma), or the end of the study period (12-31-2015). Rates of all site cancer and lymphoma for these time intervals in 5-year age groups (20-24 through 85+) were obtained from SEER*Stat version 8.3.5. Standardized incidence ratios (SIRs) were calculated for each time period by dividing the observed number of cancers in RA patients to the expected numbers obtained by applying the SEER rates.

Results: We identified 50,870 male US Veterans who fulfilled our RA algorithm and eligibility criteria. The mean (SD) age was 64 (11) years, 80% were white, 13% black, 60% were current or former smokers, 65% were RF positive and 62% were anti-CCP positive. Among these patients, 4435 all site cancers and 461 lymphomas were observed. Relative to SEER, the highest SIRs were observed in 2001-2005 for both all site cancers (1.8, 95% CI 1.7-1.9) and lymphomas (2.9, 95% CI 2.4-3.5). We observed a decrease in SIRs for both types of cancers in 2006-2010 and then a slight increase in the last time period (Figure 1).

Conclusion: To our knowledge, this is the first study evaluating incidence trends of all site cancers and lymphoma in a national cohort of veteran RA patients. We observed higher rates of both all site cancers and lymphomas, in the veteran RA population compared to the SEER population, but the trend was toward decreasing risk over more recent years compared to a similarly-aged non-RA population.   

Figure1. Trends in All Site Cancer and Lymphoma Incidence in veteran RA patients compared with the US general population