Cancer risk in patients hospitalized with polymyalgia rheumatica and giant cell arteritis: a follow-up study in Sweden

Objectives. Studies reporting cancer risk after PMR and GCA are few, but it remains an issue of both concern and controversy. We examined the overall and specific cancer risks among Swedish subjects following hospitalization for these diseases. Methods. PMR and GCA patients were identified from the Swedish Hospital Discharge Register and by linking them with the Cancer Registry. Follow-up of patients was carried out from the last hospitalization through year 2006. Standardized incidence ratios (SIRs) were calculated in these patients compared with subjects without the diseases. Results. A total of 35 918 patients were hospitalized for PMR and GCA during the years 1965-2006; the hospitalization rate increased towards late age. A total of 3941 patients developed subsequent cancer, giving an overall SIR of 1.19; and for cancer diagnosed later than 1 year of follow-up, the SIR was 1.06. A significant excess was noted for skin (squamous cell carcinoma and melanoma), stomach, lung, prostate, kidney, nervous system and endocrine gland tumours, and additionally for non-Hodgkin's lymphoma, myeloma and leukaemia. Decreased risk was noted for endometrial cancer. Conclusions. Patients hospitalized for PMR and GCA had a marginally increased risk of cancer, with the highest risk noted for the first year after hospitalization. However, for specific cancers, such as skin cancer and leukaemia, the increases were still significant for patients diagnosed later than 1 year after hospitalization, suggesting that these could be true associations, but the mechanisms remain to be established.