Influence of inflammatory polyarthritis on cancer incidence and survival - Results from a community-based prospective study

Objective. To investigate whether the incidence of cancer is increased and whether the rate of cancer survival is reduced in patients following the onset of inflammatory polyarthritis. Methods. Between 1990 and 1999, we recruited 2,105 patients to a large primary care-based register of new-onset inflammatory polyarthritis. Subsequent cancers were ascertained by linkage to hospital and death records and were confirmed by the regional cancer register. Cancer incidence, both all-site and site-specific, was compared with regional rates, adjusting for age, sex, and calendar year. Overall cancer survival, adjusted for site, was compared with regional data using Kaplan-Meier curves and Cox regression. Results. There were 123 incident cases of cancer in the cohort of patients with inflammatory polyarthritis. The overall incidence of cancer among this cohort of patients with inflammatory polyarthritis was not increased compared with that in the regional population. Among cancers of all major organ systems, only the incidence of hematopoietic cancers (including lymphoma) was increased. Five-year cancer survival was reduced in patients with inflammatory polyarthritis compared with patients without inflammatory polyarthritis. After adjusting for diagnosis, age, sex, and tumor type, mortality in patients with inflammatory polyarthritis and cancer was significantly increased (hazard ratio 1.4, 95% confidence interval 1.1-1.7). Conclusion. This is the first investigation of overall cancer survival in patients with inflammatory polyarthritis. Compared with an increased incidence of cancer, reduced cancer survival might be a greater contributor to the increased cancer mortality observed in some rheumatoid arthritis populations.