To estimate the prevalence and incidence of malignancy and its types in psoriatic arthritis (PsA) and psoriasis without arthritis (PsC) patients, in comparison to the general population, and to identify the predictive factors for developing cancer in psoriatic disease (PsD).
PsA patients followed prospectively since 1978 and PsC patients followed since 2006 at 6-to-12 month intervals according to a standard protocol were included. Malignancies were recorded prospectively and linkages with Cancer Care Ontario and the Death Registry were carried out to confirm the presence and type of malignancy up to December 2016. Standardized incidence ratios (SIR) were calculated for overall cancers and by age and sex. Cox regression analysis was conducted to identify risk factors associated with the development of malignancy after the diagnosis of PsD.
2051 patients (PsD) were included of whom 228 (11%) developed cancer. 168 patients developed cancer after first clinic visit and are included in this report. Overall SIR for malignancy was 0.83 (0.68, 1.00), SIR for females was 1.06 (0.80, 1.37), and for males was 0.67 (0.50, 0.88). The most common malignancies were skin, breast, and hematological. Skin cancer was the only specific cancer that had a higher incidence than the general population with SIR = 3.37 (1.84, 5.66). There was insufficient evidence to suggest an increased risk of malignancy associated with biologics use.
In this long-term prospective follow-up of patients with PsA and PsC the overall malignancy risk was not found to be higher than the general population, while skin cancer increased.