Patients diagnosed with RA have been at an increased risk of many cancers and at a decreased risk of some cancers. We planned to revisit the theme by using a nation-wide population of RA patients.
An RA research database was constructed by identifying hospitalized RA patients from the Hospital Discharge Register and cancer patients from the Cancer Registry. Earlier studies from Sweden have shown that some 75% of RA patients have been hospitalized at some time point. Follow-up of 42,262 RA patients was carried out from year 1980 to 2004 including separate follow-ups for shorter intervals. Standardized incidence ratios (SIRs) were calculated for cancer in RA patients by comparing with subjects without RA.
Many cancers were in excess in RA patients, especially Hodgkin disease, non-Hodgkin lymphoma and squamous cell skin cancer; a novel association was found for non-thyroid endocrine tumours. Colon, rectal and endometrial cancers were decreased in RA patients. When RA patients were first hospitalized after 1999, the SIRs for melanoma, squamous cell skin and upper aerodigestive tract cancers and for leukaemia were increased compared with previous periods.
This study, the largest so far published, quantified the increased and decreased site-specific risks of cancer in RA patients. The recent increases in the risks of squamous cell skin and upper aerodigestive tract cancers, melanoma and leukaemia call for continuous vigilance and recording of changes in treatment.