Incidence of cancer in a cohort of Spanish patients with systemic lupus erythematosus.

OBJECTIVE: To determine the incidence and prevalence of cancer in a cohort of patients with systemic lupus erythematosus (SLE) and identify associated risk factors. PATIENTS AND METHODS: The study comprised a dynamic cohort of SLE patients (November 1989 to December 2006) at a tertiary referral centre. An adjusted external control from the hospital tumour registry was used.
RESULTS: The study included 175 SLE patients (90% women), with a mean time at risk of 1370.5 patient-years. Fourteen women (8%) died, mainly from cardiovascular events. No patient died due to malignancy. We found 35 tumours in 28 patients, 25 of them after the diagnosis of SLE, of which 5 were malignant. The rate of benign tumours was 14.6/1000 patient-years (95% CI, 8.9-22.5) and of malignant tumours 3.6/1000 patient-years (95% CI, 1.5-8.8), with a crude incidence odds ratio for malignant tumours of 3.5 (95% CI, 1.5-7.9). However, this significance was lost after standardizing the rates. Concerning associated risk factors, differences were found in the mean erythrocyte sedimentation rate [HR 1.4 (1.1-1.7)], and the presence of thrombosis [HR 6.9 (1.49-41.2)], especially arterial thrombosis.
CONCLUSIONS: We found a crude incidence rate of cancer that was almost four times greater in our SLE patients as compared with the expected rate in the hospital area of western Malaga.