Phototherapy in psoriasis (including a summary of NICE guidance)

Secondary care management option for psoriasis.

• benefits of sunlight in psoriasis are well recognised
  • led to the development of phototherapy units, which emitted UV light of different wavelengths (UVA 320-400nm and UVB 290-320nm)

NICE suggest that (1):

• phototherapy (broad- or narrow-band ultraviolet B light)
  • narrowband ultraviolet B (UVB) phototherapy should be offered to people with plaque or guttate-pattern psoriasis that cannot be controlled with topical treatments alone
  • treatment with narrowband UVB phototherapy can be given 3 or 2 times a week depending on patient preference. Tell people receiving narrowband UVB that a response may be achieved more quickly with treatment 3 times a week
    
    
• alternative second- or third-line treatment should be offered when:
  • narrowband UVB phototherapy results in an unsatisfactory response or is poorly tolerated or
  • there is a rapid relapse following completion of treatment (rapid relapse is defined as greater than 50% of baseline disease severity within 3 months) or
  • accessing treatment is difficult for logistical reasons (for example, travel, distance, time off work or immobility) or
  • the person is at especially high risk of skin cancer
    
    
• consider psoralen (oral or topical) with local ultraviolet A (PUVA) irradiation to treat palmoplantar pustulosis
  
  
• when considering PUVA for psoriasis (plaque type or localised palmoplantar pustulosis) discuss with the person:
  • other treatment options
  • that any exposure is associated with an increased risk of skin cancer (squamous cell carcinoma)
  • that subsequent use of ciclosporin may increase the risk of skin cancer, particularly if they have already received more than 150 PUVA treatments
  • that risk of skin cancer is related to the number of PUVA treatments
    
    
• do not routinely offer co-therapy with acitretin when administering PUVA
  
  
• consider topical adjunctive therapy in people receiving phototherapy with broadband or narrowband UVB who:
  • have plaques at sites that are resistant or show an inadequate response (for example, the lower leg) to phototherapy alone, or at difficult-to-treat or highneed, covered sites (for example, flexures and the scalp), and/or
  • do not wish to take systemic drugs or in whom systemic drugs are contraindicated
    
    
• do not routinely use phototherapy (narrowband UVB, broadband UVB or PUVA) as maintenance therapy.

UVB treatment:

Is an effective treatment method for guttate or plaque psoriasis which is resistant to topical therapy (2).

There are 2 types of UVB treatment:

• broad band ultraviolet radiation - most effective waveband is around 290-320 nm
• barrow band
  
• spectrum of around 311nm is most effective for treatment of psoriasis - phototherapy bulbs with an output in this range have been developed and are used in narrowband UVB (nUVB) therapy
• nUVB therapy (311-313nm) is more effective than conventional broadband UVB with respect to clearing times and remission
• nUVB is administered three times per week (similar treatment schedule as used with broadband UVB)
• nUVB is less erythemogenic than broadband UVB and has mainly replaced it as a treatment for psoriasis

Contraindications to UVB therapy include:

• patients with a history of skin maliganacies
• SLE
• Xeroderma pigmentosum (1)

Side effects of UVB treatment:

• acute skin burn
• with longterm use, risk of skin malignancy (2)

nUVB in comparison to photochemotherapy (PUVA)

• nUVB-treated patients do not have to take tablets or wear protective eyewear
• nUVB can also be used during pregnancy and in children (2)
• nUVB is thought to be less carcinogenic than PUVA

PUVA photochemotherapy

• it is used in patients with severe psoriasis resistant to topical treatment and UVB
• combination of oral or topical psoralen and subsequent irradiation with long-wave UVA light (Psoralens + UVA = PUVA)
• oral psoralen (8-methoxypsoralen) is usually taken 2 hours prior to UVA irradiation and should be taken with a light meal in order to ensure constant and optimal drug absorption throughout a course of PUVA (2)
• oral psoralen can cause nausea - patients must wear protective eyewear on the treatment days (24 hours from the time of psoralen ingestion) to prevent cataract formation (2)
• topical PUVA - patients apply psoralen paint or gel to the skin or soak in a bath of psoralen solution prior to light exposure
• remission is variable and patients will require repeat courses
• there is a risk of nonmelanoma skin cancers associated with prolonged PUVA therapy (associated to with the number of treatments or the cumulative dose of UVA) (2)
• PUVA therapy is often combined with other treatments such as retinoids and vitamin D analogues to reduce the number of exposures required for clearance (2)

Reference:

• 1. NICE (September 2017). Psoriasis - the assessment and management of psoriasis
• 2.The British association of dermatologists. Psoriasis - General management, phototherapy
• 3. Prescriber (2005); 16(8).
• 4. Prescribers' Journal (1993); 33(5):183-91.