The researchers identified 16 cases of Bowen disease and 79 cases of nonmelanoma skin cancer in the study population. However, the incidence rates of the conditions were similar across all the groups in the study, and there was no increase in HR for either condition relative to the number of phototherapy sessions.
The investigators also found 34 instances of melanoma, but they did not find an increase in the risk of the condition related to the number of NBUVB phototherapy sessions.
Of all patients in the study, 717 received 500 or more NBUVB phototherapy sessions. In this subgroup, there were 7 cases of actinic keratosis, 1 instance of Bowen disease, and 1 instance of nonmelanoma skin cancer. There was no increased risk of actinic keratosis, Bowen disease, nonmelanoma skin cancer or melanoma among these patients.
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Previous research has shown that genetic variations in patients with vitiligo may shield them from skin cancer and boost their immune response.4,5 It is possible that the greater immune response in these patients also protects them against potential skin cancer due to multiple sessions of NBUVB phototherapy, wrote the authors.
“It seems that patients who have vitiligo seem to possess some natural type of immunity to these more aggressive skin cancers,” Michele S. Green, MD, a dermatologist at Lenox Hill Hospital in New York City, who was not involved in the study, said in an email. “Future studies should center on what is unique genetically that may help protect them and others against the risk of skin cancers.”
“I thought it was a well-done study,” said Nada Elbuluk MD, MSc, a clinical associate professor in the department of dermatology at the University of Southern California in Los Angeles, who was not involved in the new research. “I think it is an important study because we need to investigate this question for our vitiligo patients who are getting phototherapy, which many of them are.”
As for the greater risk of actinic keratosis in some patients, Dr Elbuluk did not see it as a cause for concern, because there was no increase in skin cancer risk in the study population. “I don’t think it is something to worry about, but I do think all vitiligo patients — just like the general population — should be getting full-body skin exams once a year with a board-certified dermatologist,” she said. “So that way, if anything does come up, it is caught early and it is treated.”
She pointed out that, as the authors of the paper hypothesized, the increased immune response in patients with vitiligo may help to not only protect them from skin cancer, but also may prevent any actinic keratoses from developing into skin cancer. “That’s still a question to be answered, but it is possible given that we are not seeing higher rates of skin cancer in this population,” she said.
Until now, there was no solid evidence showing how long it was safe to administer narrowband UV-B to patients with vitiligo, said John E. Harris, MD, PhD, director of the Vitiligo Clinic and Research Center at the University of Massachusetts in Worcester, who was not involved in the study. “I think that this paper now allows us to feel comfortable treating our vitiligo patients and giving them the therapy that they need and deserve,” he said.
Rebecca Hartman, MD, MPH, a dermatologist at Dana-Farber Cancer Institute in Boston, Massachusetts, who was not involved in the study, said that more research is needed to see if the findings could be generalized to other populations. “Skin cancer is much more common in non-Hispanic whites, so I am not sure how applicable it is to the US, where I practice,” she said.
References
- Kozma B, Eide MJ. Photocarcinogenesis: an epidemiologic perspective on ultraviolet light and skin cancer. Dermatol Clin. 2014;32(3):301-313, viii.
- Valejo Coelho MM, Matos TR, Apetato M. The dark side of the light: mechanisms of photocarcinogenesis. Clin Dermatol. 2016;34(5):563-570.
- Bae JM, Ju HJ, Lee RW, et al. Evaluation for skin cancer and precancer in patients with vitiligo treated with long-term narrowband UV-B phototherapy [published online on March 11, 2020]. JAMA Dermatol. doi: 10.1001/jamadermatol.2020.0218
- Wu W, the 23andMe Research Team, Amos CI, et al. Inverse relationship between vitiligo-related genes and skin cancer risk. J Invest Dermatol. 2018;138(9):2072-2075. doi: 10.1016/j.jid.2018.03.1511
- Jin Y, Andersen G, Yorgov D, et al. Genome-wide association studies of autoimmune vitiligo identify 23 new risk loci and highlight key pathways and regulatory variants. Nat Genet. 2016;48:1418-1424.
