Cancer Research Lab

Except for hematopoietic cancers, cancer incidence is no more common among patients with inflammatory arthritis than in the general population, investigators in the UK report. However, 5-year cancer survival is significantly reduced.

Mortality among patients with rheumatoid arthritis is about twice as high as that of the general population, Dr. Alan Silman and his associates note, and mortality related to cancer is also increased. What remains unsettled is whether the higher mortality is due to greater incidence or a higher case fatality rate.

Dr. Silman, from the University of Manchester, and associates performed a prospective study to assess the risk of cancer among patients with new-onset inflammatory polyarthritis. This unselected cohort of 2,105 patients was enrolled in the Norfolk Arthritis Register between 1990 and 1999.

According to their paper in the March issue of Arthritis and Rheumatism, patients were examined annually, and were excluded if they were diagnosed with conditions other than rheumatoid arthritis, psoriatic arthritis, or postviral arthritis.

Cancer diagnoses were ascertained by linkage to hospital and death records. The authors considered only primary cancers that occurred at least 1 year after the onset of the arthritis symptoms. Follow-up was maintained until 2004, during which time 123 cancer cases were diagnosed.

After adjusting for age and gender, cancer incidence was no higher among patients. The only outlier was hematopoietic cancer, for which the relative risk was 1.6.

Nonetheless, “after adjustments were made for age, sex, and (cancer) site, inflammatory polyarthritis patients with cancer had a statistically significant increased risk of death compared with the general Norfolk population with cancer (hazard ratio 1.4),” they report.

Dr. Silman’s group observed that when all digestive disease cancers were combined, the hazard ratio was 1.9; for hematopoietic cancer, the hazard ratio was 1.8.

The researchers chose patients with inflammatory polyarthritis, because diagnostic criteria at baseline “are unstable in patients with early arthritis.” Nearly 60% of their cohort was diagnosed with rheumatoid arthritis during the first 5 years of follow-up.