Background Psoriasis is a chronic inflammatory disease that involves hyperproliferation of keratinocytes in the epidermis. Several studies have reported the relationship between psoriasis and cancer. Population-based estimates for cancer risks in patients with psoriasis is rare

Objectives This study estimated the standardised incidence ratio (SIR) of cancer in patients with psoriasis in Taiwan.

Methods The primary data source was the National Health Insurance database of Taiwan. We identified patients with psoriasis based on a rheumatologist or dermatologist diagnosis. Incident cases who were free or cancers in 2000 were identified. Incidence of cancer was estimated in both incident psoriasis patients and the general population in 2000. To measure the relative risk of cancer in psoriasis patients, we calculated a SIR for all types of cancers and also each cancer type. SIRs were computed as ratios of observed numbers of cancers to the expected number of cancers on the basis of age-specific incidence rates in 5-year age intervals of the entire NHI covered population in 2000.

Results A total of 6,835 incident psoriasis patients (4,472 men, 2,363 women) were identified from 21,226,181 cancer-free beneficiaries of NHI in 2000. Mean age was 46.96 years in men and 41.27 years in women. After a median follow-up of 11 years, cancer was diagnosed in 527 patients with psoriasis and 860,084 in the general population. The most common cancers sites were gastrointestinal tract, oral cavity and pharynx in patients with psoriasis. The overall incidence of cancer was higher in psoriasis patients than the general population (6.92 vs. 3.34 cases per 1,000 patient-years, P<0.001). Psoriasis was associated with an SIR of 1.15 (95% confidence interval [CI], 1.06–1.25) for cancer of all sites. The SIR was 1.95 (95% CI, 1.21–3.14) for skin cancers, 1.59 (95% CI, 1.26–2.02) for oral cavity and pharynx cancers and 1.14 (95% CI=1.00–1.30) for gastrointestinal tract cancers, respectively.

Conclusions Compared with the general population, psoriasis patients have an increased risk for cancer.

Disclosure of Interest None declared