Higher Incidence of Skin Cancer Observed in Vitiligo, Psoriasis Patients Receiving Phototherapy

Brian Keng Yong Chia, MBBS

New research indicates that patients with vitiligo or plaque psoriasis using narrowband ultraviolet B (NBUVB) phototherapy treatments have higher rates of skin cancer than the general population.

Patients’ use of phototherapy for psoriasis, vitiligo, and atopic dermatitis has been widespread since the 1980s. The risk of non-melanoma skin cancers (NMSCs) related to NBUVB phototherapy has been unclear, given mixed study results on predominantly Caucasian study populations.

This study, led by Brian Keng Yong Chia, MBBS, of the National Skin Centre of Singapore, sought to examine the relationship between skin cancer rates and the use of phototherapy by dermatology patients in Singapore.

“The aim of our study is to investigate the risk of skin cancer in patients receiving NBUVB phototherapy for psoriasis and vitiligo in our dermatology centre in Singapore with diverse ethnicities in a predominantly Asian population,” Chia and colleagues wrote.

Background and Research

The investigators conducted a 9-year retrospective study, assessing patients with psoriasis and vitiligo who were receiving NBUVB phototherapy treatment from the National Skin Centre of Singapore, using a total of 3,730 participants. The study participants had received phototherapy during a 9-year timeframe from 2004 to 2013.

The research team included participants who had been treated with both whole body and localized phototherapy. The investigators recorded patient demographics such as gender, race, age, and Fitzpatrick skin type. Additionally, they would include such information as:

• Patients’ primary treatment indication (psoriasis or vitiligo)
• Phototherapy-related treatment factors including cumulative dosage, maximum dosage, number of treatments, dosage per treatment session
• Any other treatments patients were given such as systemic or topical therapy

The investigators used the patients’ data to match their identification numbers to Singapore’s National Registry of Diseases Office database and to then collected data on each and every skin cancer diagnosis.

Findings

The investigators concluded that the age-standardized incidence of skin cancer for patients with psoriasis or vitiligo who had been given phototherapy treatment was 47.5 and 26.5, respectively. They note that this rate is larger than rates of skin cancer incidence among the general population.

Additionally, the researchers noted that skin malignancy risk was positively correlated with both maximum phototherapy dose (P=0.011) and the cumulative dose (P=0.008), as well as participants’ previous systemic treatments (P=0.006).

“The risk of skin malignancy is higher with psoriasis patients, greater cumulative and maximal dose of phototherapy as well as use of systemic therapy,” they wrote. “Despite the increased risk, the absolute number of skin malignancies remains low, especially for vitiligo patients, with no cases of melanoma diagnosed – a reassuring finding that phototherapy remains a safe alternative in the treatment of psoriasis and vitiligo.”

The study, “Incidence of skin malignancies in patients with vitiligo or psoriasis who received narrowband ultraviolet B phototherapy: a retrospective review of 3730 patients,” was published in Photodermatology, Photoimmunology & Photomedicine.