A research letter published by the Journal of the American Academy of Dermatology dove into the question of how psoriasis may increase the overall risk of cutaneous malignant melanoma in patients.
A Swedish investigation wanted to further analyze the link between psoriasis and cutaneous malignant melanoma (CMM).1 Psoriasis patients have been studied to have a higher risk of cancer overall.2 Currently, the risk increase is particularly robust for keratinocyte carcinomas, but for CMM the connection remains uncertain because results from different studies are heterogeneous.3-6
A comparative registry-based cohort study was conducted to measure patients with psoriasis using the time from 2001 to 2016. To each such patient, 5 population-derived age, sex, and geographically matched control individuals were selected, according to the letter. The CMM incidences in the respective groups were then calculated, and adjusted Poisson regression as well as adjusted Cox proportional hazards regression models were used.
There were 61,692 patients with psoriasis and 300,421 matched control individuals were included in the cohort study. The patients had a median age (interquartile range) of 53.2 years (39.3-63.6), and 49.6% were male. The median follow-up periods for the psoriasis cohort and the control group were both 8.6 years.
For the patients with psoriasis and control subjects, CMM occurred in 579 (incidence rate, 123.2 cases per 100,000 person-years) and 2133 individuals (incidence rate, 92.1 cases per 100,000 person-years), respectively, yielding an adjusted incidence rate ratio (IRR) of 1.29 (95% confidence interval [CI], 1.18-1.40; P < .0001).1 There was an increase in IRR comparing the data of patients with severe psoriasis (n = 21,446; 34.8%) with their matched control individuals compared to the corresponding IRR for those without severe psoriasis (1.48 vs 1.18; P = .012).
The data was then divided into invasive and in situ melanoma where it was found an increased risk for patients with psoriasis was observed in both groups but was more conspicuous for in situ melanomas. A significantly increased IRR for CMM was seen in all age groups except for women older than 50 years at the index date, the article continued. Psoriatic arthritis (PsA) history did not affect the IRR, however a past of actinic keratosis (AK) did. The risk for CMM for patients with a history of AKs was shown to have a significant increase (IRR, 3.03; 95% CI, 2.51-3.65; P < .0001). Contrarily, patients without a history of AK did not have a significantly increased risk for CMM compared to their matched control individuals (IRR, 1.05; 95% CI, 0.95-1.17; P = .30).
The adjusted hazard ratios were:
Also, the number of patients with psoriasis and a first CMM (n = 579) who developed a second CMM (n = 62, 10.7%) was the same as those in the corresponding control individuals (183 of 2133 [8.6%]; P = .12). The results were robust in 3 sensitivity analyses where the inclusion criteria were altered.
This investigation was limited by the retrospective design and inability to obtain important CMM risk factors, including family history of CMM, nevus count, and history of ultraviolet exposure as well as light therapies.1
“To summarize, our findings suggest that patients with psoriasis are at an increased risk for CMM, including in situ melanoma,” the authors concluded.