Psoriasis - Phototherapy

Side Effects of UVB. The treatment can cause itching and redness. UVB radiation from sunlight is known to increase the risk for skin cancers. There is no strong evidence, however, that UVB treatments pose any risk for skin cancers except on male genitalia, which can be significant (4.5%) at high doses.

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Narrow Band Ultraviolet B (NB-UVB) Radiation

Narrow band NB-UVB radiation uses fluorescent lighting that emits radiation in a specific range between 310 and 312 nm, which, theoretically, is the most beneficial component of sunlight. Exposure times are shorter but of higher intensity than with broadband UVB.

Clearance of 75% typically occurs after 10 to 12 treatments. NB-UVB treatments performed three times a week achieve results that are equal to twice-weekly PUVA treatments. (Weekly NB-UVB treatments are not effective.) It is also probably less likely than PUVA to cause skin cancers. Studies are mixed on whether its remissions rates are equal to those of PUVA, but the weight of evidence is currently positive.

Patients prefer this approach over other PUVA treatments because they do not have to wear protective eyewear, take medications, or experience unpleasant side effects, notably nausea. It is also safe for pregnant women and children.

Some experts, then, believe that NB-UVB should be the first choice for patients with chronic plaque, with PUVA reserved for patients who fail.

According to one 2002 study, however, NB-UVB does not have any affect on the disease process itself. In the study NB-UVB radiation only affected the specific areas of skin that it targeted. Given these results, it is not clear, then, if this approach has any significant long-lasting value for treating chronic psoriasis. Combinations with topical agents, such as tazarotene or psoralens, may improve its effectiveness.

Laser Treatments

Laser UVB Treatment. A recent variation of a device called an excimer laser (Xtrac) delivers a precise UVB wavelength of 308 nm. The excimer laser is more effective than narrow-band UVB (NV-UVB) for localized psoriasis, since it allows targeting of very specific areas of skin. (It is not suitable for the scalp, however.) Generally, eight to 10 treatments administered twice a week are needed to clear psoriasis. Remission rates are similar to NB-UVB, but the excimer laser can clear the psoriasis faster and at lower doses. It also spares the healthy skin around it. Blistering is a common side effect. More comparison studies are needed to determine risk and benefits compared to NB-UVB, particularly any long-term risk for skin cancer.