Malignancies in patients with spondyloarthritis with and without concomitant psoriasis, and the effect of disease modifying anti-rheumatic drugs

Objectives To determine the risk of 6 types of malignancies in spondyloarthritis (SpA) with and without psoriasis (PsO) and on disease-modifying anti-rheumatic drugs (DMARDs), compared to non-specific back pain (NSBP). Methods Medical records were retrieved. Patients with SpA with and without PsO were identified and compared to those with NSBP. Clinical data; follow-up duration; comorbidities; dates and types of cancer diagnosed; types and duration of DMARD therapy were collected. Propensity score adjustment was used to compare the risks of malignancies between SpA, SpA with and without PsO, and NSBP. Cox regression analysis was used to determine the risk of malignancy in DMARD therapy. Results A total of 3020 patients with SpA and 2527 patients with NSBP were studied. The mean follow-up duration in patients with SpA and NSBP was 9.6 years and 13.5 years respectively. Incidence and risk of malignancies were compatible between SpA and NSBP. The incidences of various carcinomas (per 1000 patient-years) in SpA were: 1.37 for colorectal carcinoma; 0.30 for carcinoma of pancreas; 0.30 for carcinoma of stomach; and 0.91 for lymphomas. Risk of colorectal carcinoma (HR 2.46; p=0.03) and lymphomas (HR 2.86; p=0.04) was increased in SpA with concomitant PsO. DMARD therapy was not associated with increased risks of malignancies after adjustment for confounding factors. Conclusions Risk of malignancy was increased in SpA with PsO but not in other subtypes of SpA or DMARD therapy.