Myth: UVB phototherapy causes skin cancer
Phototherapy is a common treatment modality for psoriasis patients that can be used in the physician’s office or psoriasis clinic or at home. Options include UVB phototherapy (broadband and narrowband), which slows the growth of affected skin cells; psoralen plus UVA (PUVA), which slows excessive skin cell growth; and excimer laser therapy, which targets select areas of the skin affected by mild to moderate psoriasis and is particularly useful for scalp psoriasis. Each of these therapies may be combined with other topical and/or systemic psoriasis treatments. The effects of UV light on the skin and the connection to skin cancer is widely known. Therefore, patient education on the risk for skin cancer with phototherapy is essential.
Evidence suggests that UVB phototherapy remains a safe treatment modality. In a 2005 analysis of prospective and retrospective studies on skin cancer risk from UVB phototherapy, 11 studies (10 concerning psoriasis patients) were reviewed and the researchers concluded that all studies eventually showed no increased skin cancer risk with UVB phototherapy. One of the PUVA cohort studies examined genital skin cancers and found an increased rate of genital tumors associated with UVB phototherapy.
Another analysis to define the long-term carcinogenic risk for narrowband UVB treatment found that there was no association between narrowband UVB exposure alone (without PUVA) and any skin cancer. For patients treated with narrowband UVB and PUVA, there was a small increase in basal cell carcinomas.
Dermatologists should monitor psoriasis patients for self-administered treatment with tanning beds. Based on a questionnaire sent to approximately 14,000 subscribers of National Psoriasis Foundation emails, 62% of 617 tanners started tanning to treat psoriasis; they were more likely to have received medical phototherapy and had more severe psoriasis. Approximately 30% of these patients indicated that they used tanning as a self-treatment for psoriasis because of the inconvenience and cost of UV light treatment in a physician’s office as well as treatment failure of other therapies prescribed by the physician. “Our results imply that tanning bed usage among psoriasis sufferers is widespread and linked with tanning addiction,” reported Felton et al. “Practitioners should be particularly vigilant to the possibility of tanning bed usage in at-risk patients.” These patients may be at increased risk for skin cancer. Problematic tanning behaviors may be seen in younger female patients diagnosed with psoriasis at an early age as well as patients with severe psoriasis who were previously prescribed phototherapy treatment.
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