Background/Purpose: to determine the incidence and time trends of malignancy in patients with rheumatoid arthritis (RA) in 1980-2007 compared to individuals without RA from the same population.

Methods: A population based inception cohort of patients with RA who fulfilled 1987 ACR criteria in 1980-2007 and an age and sex matched cohort of non-RA subjects from the same population was assembled and followed until death, migration or 12/31/2008. Incidence rates of overall and site specific malignancy were collected. Cumulative incidence of malignancy adjusted for the competing risk of death was estimated for RA and non-RA subjects and compared using Gray’s test.

Results: The study consisted of 813 RA and non-RA subjects (mean age 55.9 years, 68% female, 66% rheumatoid factor positive). Prior to RA incidence/non-RA index date, 53 RA and 66 non-RA subjects had a malignancy (p=0.22). The prevalence of hematologic malignancy was lower among RA subjects compared with non-RA subjects prior to the incidence/ index date, (n=0 vs n=7, p=0.015). Excluding patients with prior malignancies, the remaining RA patients were followed for a mean of 9.1 years (mean 10.3 years for non-RA) during which 109 RA and 94 non-RA subjects developed a malignancy. The cumulative incidence for hematologic malignancy was higher among RA than non-RA subjects (2.0% ± 0.6% vs 0.7% ± 0.3% at 10 years, p=0.009). There was no significant difference in the cumulative incidence of overall malignancy between RA and non-RA subjects (13.0% ± 1.5% vs 9.1% ±1.2% at 10 years, p=0.10). There was no significant difference in the rate of lung or colon cancer in RA subjects relative to non-RA subjects. The cumulative incidence of breast cancer was lower among RA subjects compared to non-RA in the first 10 years after diagnosis of RA (2.9% ± 0.8% vs 1.6% ± 0.7% at 10 years), but this difference did not achieve statistical significance (p=0.63).  Individuals diagnosed with RA more recently (1995-2007) were more likely to develop a hematologic malignancy compared with RA subjects diagnosed in earlier years (1980-1994) (hazard ratio [HR]: 2.28; 95% CI 0.95, 5.51). Similar changes were not seen over the same time period among subjects without RA.

Conclusion: Patients diagnosed with RA more recently appear to be at higher risk of developing a malignancy relative to patients diagnosed in earlier years. There was no significant difference in the rate of solid organ malignancies including breast, lung and colon cancer between RA and non-RA subjects in this population. The rate of hematologic malignancy is higher among patients with RA relative to non-RA subjects.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/incidence-and-time-trends-of-malignancy-in-rheumatoid-arthritis-a-population-based-study-1980-2007/