Aspirin (ASA) and also nonsteroidal anti-inflammatory drug (NSAID) use has been associated with a low incidence of colorectal cancer. The incidence of colorectal cancer in a cohort of patients with rheumatoid arthritis (RA) is reported here.
Cancer incidence was studied in a cohort of 9469 persons hospitalized for RA during 1970-1991 in Finland. The follow-up time was about 65,400 person-years.
The incidence of colon cancer was significantly lower than in the general population [standardized incidence ratio (SIR) 0.57; 95% confidence interval (CI) 0.33-0.93], and the combined SIR for colorectal cancer was 0.62 (95% CI 0.42-0.88), while the combined incidence of all malignancies (SIR 1.16; 95% CI 1.07-1.26) was higher in RA patients than in the general population.
Chronic use of NSAIDs or ASA, including antiinflammatory doses, is probably the main explanation for the low incidence of colorectal cancer in RA patients.