Psoriasis Increases Cancer Risk

Lone Skov, MD, PhD, DMSC

Patients with psoriasis have an increased risk of cancer, recent study findings revealed.

Lone Skov, MD, PhD, DMSC, and colleagues from the University of Copenhagen conducted a systematic review and meta-analysis to evaluate the association and risk of cancer in patients with psoriasis or psoriatic arthritis.

The findings showed patients with psoriasis had a slightly higher risk of keratinocyte cancer and lymphomas.

Skov, from the Department of Dermatology and Allergy at Herlev and Gentofte Hospital at University of Copenhagen, and the team assessed 365 original studies that reported the incidence or prevalence of cancer in patients with the skin condition or psoriatic arthritis. Two investigators searched PubMed and Embase from inception through January 2019 to find studies.

The investigators used the search terms “psoriasis” or “psoriatic” and “neoplasms,” “malignancy,” or “cancer.” The team limited analysis to include: all cancer; cancer excluding keratinocyte cancer; keratinocyte cancer; melanoma; lymphoma overall; non-Hodgkin lymphoma; Hodgkin lymphoma; and breast, lung, colorectal, colon, rectal, and bladder cancer.

Studies were excluded if they did not fall into >1 category and if they only investigated a pediatric population.

If available, the investigators collected information including age; sex; number of patients with psoriasis or psoriatic arthritis; assessment of psoriasis or psoriatic arthritis; and number of patients with psoriasis or psoriatic arthritis and cancer.

Skov and the team included 112 studies in their qualitative assessment and data extraction. The studies comprised 2,053,932 patients with the conditions.

Overall cancer prevalence in patients with psoriasis was 4.78% (95% CI, 4.02-5.59). The prevalence decreased to 4.06% (95% CI, 3.31-4.87) when keratinocyte cancer was excluded. Per 1000 person-years, the incidence rate for overall cancer was 11.75 (95% CI, 8.66-15.31) and 7.61 (95% CI, 6.53-8.77) when keratinocyte cancer was excluded.

There was also an increased risk of several specific cancers, including keratinocyte cancer (RR, 2.28; 95% CI, 1.73-3.01); lymphomas (RR, 1.56; 95% CI, 1.37-1.78); lung cancer (RR, 1.26; 95% CI, 1.13-1.4); and bladder cancer (RR, 1.12; 95% CI, 1.04-1.19).

In patients with psoriasis, there was an increased risk of developing both Hodgkin and non-Hodgkin lymphoma, possibly due to an increased risk of cutaneous T-cell lymphoma in such patients, the study authors wrote.

There was no increased risk of cancer for patients with psoriasis who were treated with biologic agents (RR, .97; 95% CI, .85-1.1) compared to patients who received conventional therapy. The risk of cancer decreased when the team excluded keratinocyte cancer.

Psoriatic arthritis was not linked with an increased risk of cancer overall (RR, 1.02; 95% CI, .97-1.08).

The overall cancer prevalence in patients with psoriatic arthritis was 5.74% (95% CI, 3.64-8.28) with an incidence rate of 6.44 (95% CI, 4.8-8.32). None of the included studies found a significant association between psoriatic arthritis and cancer overall (RR, 1.02; 95% CI, .97-1.08).

There was a significant link between psoriatic arthritis and increased risk of breast cancer.

The increased risk of cancer overall for patients with psoriasis may be due to lifestyle factors such as smoking and alcohol consumption, which are often associated with the condition.

Clinicians who treat patients with psoriasis should be aware of the increased cancer risk, especially for lymphomas because immunogenic treatment could exacerbate it, the investigators concluded.

The study, “Prevalence, Incidence, and Risk of Cancer in Patients With Psoriasis and Psoriatic Arthritis,” was published online in JAMA Dermatology.