Phototherapy with Ultraviolet Light Type B (UVB) in Psoriasis (For Professionals)

Treatment of psoriasis is step by step:

• The base and most important is education and support
• Then comes topical treatment
• Then comes systemic treatment and/or phototherapy

Does UVB (Ultraviolet type B) have a role to play in the treatment in psoriasis?

• US Survey on 387 dermatologists and asked what treatment they would use as first line therapy:

“Healthy adults with 10% BSA (Body Surface Area affected) not working on topicals and health affected”

• UVB was answered as the first line therapy in 40% in men up to 60% in women. The difference is because use of methotrexate and retinoids is risky in women of childbearing age.
• Phototherapy is therefore still the champion for clinicians !

What is the most effective treatment: systemic treatment or phototherapy ?

• Study done in 713 patients from 10 medical centers

…with moderate to severe psoriasis
…on monotherapy (using one treatment)

• Out of the patients: the following proportion were “Clear or almost clear” with:

1. Methotrexate (MTX): 23.8% of cases
2. Adalimumab: in 47.7% of cases
3. Ustekimumab and Etanercept in around 30% of cases
4. Phototherapy: in 26% of cases.

• Phototherapy appears slightly less effective than the other biologics. However, there is a huge cost difference. UVB is cost effective. With one year of treatment with biologics, one can buy one phototherapy machine !

How does phototherapy work in psoriasis?

• It is somewhat still speculative
• It acts on keratinocyte hyperproliferation and immune activation

• UVB action on immune activation:

1. Induces apoptosis of activated T cells
2. Induction of T-regulatory cells

• UVB action on keratinocyte hyperproliferation

1. UVB radiation on the epidermis induces also apoptosis of epidermal keratinocytes.
2. On biopsy: staining with caspase-3 is positive and thus shows apoptosis.

Dangers of phototherapy in psoriasis

• UVB is a complete carcinogen and causes carcinogenesis in mice at high dosage
• However in psoriasis:

1. PUVA (psoralen + ultraviolet A) causes 30 times increased incidence of SCC (Squamous Cell Carcinoma) and 5 times more of BCC (Basal Cell Carcinoma)
2. 2/3 of the SCCs are located on the lower limbs
3. 150 and 350 treatments are thresholds for heightened risk of skin cancer
4. NBUVB (narrowband) is safer as it only uses on wavelength (311nm)

Contributors:

Dr Christophe Hsu – dermatologist. Geneva, Switzerland

Source of Information: Lui H, Phototherapy Update. Dubai World Dermatology & Laser Conference & Exhibition – Dubai Derma 13 – Dubai, United Arab Emirates (UAE)