Incidence and patterns of malignancies in a multi-ethnic cohort of rheumatoid arthritis patients

This study was undertaken to determine the incidence and patterns of malignancies in rheumatoid arthritis (RA) patients in our cohort.

Between 2001 and 2013, we analyzed 1117 patients in the prospective Tan Tock Seng Hospital (TTSH) RA Registry. Patients who developed malignancies after the onset of RA were identified from this registry. Age- and sex-adjusted standardized incidence ratios (SIRs) were calculated to compare observed to expected numbers of malignancies based on data from the Singapore Cancer Registry.

Out of 19 839 person-years of follow-up, 132 incident malignancies were diagnosed during the observation period. There were 114 (86.4%) solid-organ tumors and 18 (13.6%) hematological malignancies. The SIR (95% confidence interval) for all malignancies combined was 1.28 (0.88-1.87) for males and 1.21 (1.00-1.46) for females. Compared to the general population, we found a 4- to 5-fold increase in lymphoma among our RA patients compared to the general population (SIR 5.05 [1.90-13.46] for males and 3.75 [1.95-7.20] for females). The SIR of lung malignancy in male RA patients is 2.36 (1.23-4.53) and SIR of cervical malignancy in female RA patients is 3.72 (2.20-6.23).

There is a trend toward an overall increased malignancy risk in our RA patients compared to the general population. Specifically, there is an increased risk of lymphomas in all RA patients, lung malignancy in male patients, and cervical malignancy in female patients, compared to the general population.