Phototherapy
Both therapies require good metering and equipment monitoring by trained staff. All patients should be aware of the adverse effects and chronic risks, and a detailed record of an individual's treatment should be kept.
UVB Phototherapy
Broad band ultraviolet radiation in the waveband 290-320 nm (UVB), or narrow band UVB 311nm are an effective treatment of guttate or plaque psoriasis resistant to topical therapy. It is initiated by experienced dermatologistsand is administered under supervision of trained dermatology nursing staff or physiotherapists. Patient compliance is usually good, with the treatment viewed as an escape from the problems of topical agents. Restrictions in use for individual patients often relate to time off work and travel costs.
Within the UK, a range of equipment is in use. The older broad-band UVB fluorescent sources are considered less effective, in time to clear and length of remission period Narrow-band (311nm) phototherapy emits light close to the peak therapeutic wavelengths for psoriasis and has a greater efficacy than broad-band fluorescent tubes. Further guidelines on dosimetry and monitoring are available on this site (BAD guidelines)
Safety, side-effects and patient acceptability
Current human use suggests that TL-01 has a similar long-term risk to the older broad-band tubes and a reduced risk when compared to PUVA
Those patients who have a history of previous skin malignancy, systemic lupus erythematosus or xeroderma pigmentosum, should be excluded from treatment. UVB phototherapy has advantages over PUVA in that it can be used in children, during pregnancy, and does not require photoprotective spectacle use post-treatment. The principal unwanted effects of UVB phototherapy are acute skin burn, which can be avoided by careful dosimetry, and, when used over a long period, a presumed dose-related increase in the risk of developing cutaneous malignancy.
Efficacy
Although UVB phototherapy has been extensively studied, dosage regimens vary, and it seems that different skin type populations require different treatment approaches. The starting dose of UVB can be judged by estimation of the minimal erythema dose (MED). This approach is not essential, and a low dose fixed increment regimen is an acceptable alternative. A suggested approach is to start at 70% of the MED value. Subsequent doses can be increased by 40% of the immediately preceding dose, if there is no erythema, and 20% if there is a slight erythema, or held at the same exposure, if there is a marked response to the previous treatment. With such a regimen, treatments are generally given no more frequently than every two days. It is usual for a course of UVB phototherapy to take between 10 and 30 treatments to achieve clearance
Synergy with other treatments
Combination with other anti-psoriasis treatments such as tars, topical calcipotriol, and oral retinoids have been shown to be effective, increasing the rate of clearance with reduced total UVB exposure to clearance. However, most patients enjoy the freedom from topical therapies and their accompanying adverse effects, so adjunctive treatment is often reserved for resistant cases.
Photochemotherapy (PUVA)
Administration of oral or topical psoralens, followed by irradiation with long wave ultraviolet (320 to 400nm) (UVA), is an established, effective, widely used form of treatment (Psoralens + UVA = PUVA), although it is unlicensed in the UK. While it does have acute adverse effects (i.e. skin burning, nausea and pain) and chronic consequences (i.e. skin ageing, pigmentation and carcinogenicity), it continues to be used for more difficult to clear psoriasis resistant to topical preparations and UVB. Examples of different regimens for the administration of PUVA are listed in the British Photodermatology Group Guidelines for PUVA. Other detailed information sources are available.
Efficacy
Two main PUVA regimens are used. The first involves the use of the minimal phototoxic dose (MPD) to determine the first treatment dose of a course. Such an approach would be similar to that used for UVB phototherapy with, perhaps, 70% of the MPD, followed by successive doses increased by 40% increments, if there is no erythema, or 20% if the erythema response was slight. As the phototoxic effect is maximal at 48 to 72 hours, treatment is usually given twice weekly. Another approach has a fixed starting dose, which will vary with skin type, followed by fixed or percentage increments as above. No adequate studies have been published to state clearly which approach is best for a particular patient populations. It is common practice for 8-methoxypsoralen (crystalline 8-MOP) to be taken orally 2 hours prior to UVA irradiation. To achieve consistent and optimal absorption of psoralens throughout a course of PUVA, the drug should be taken with a light meal.
Safety, side-effects and patient acceptability
As there is a theoretical risk of cataract formation, patients are advised to wear eye protection for 24 hours from the time of psoralen ingestion. Further advice on eye protection can be found elsewhere on this site (BAD guidelines). If nausea occurs with 8-MOP, 5-methoxypsoralen or bath PUVA using 8-MOP or trimethoxypsoralen (TMP), can be considered. Some centres use the bath approach as the routine, preferring the confidence of knowing the drug to be at the target site, coupled with the possibility that TMP and PUVA may be less carcinogenic than oral forms.
As the risk of developing cutaneous malignancy is related to the number of treatments or the cumulative dose of UVA, PUVA-sparing measures, or alternative treatments, can be used to restrict the total amount of UVA administered. In a follow-up report on the large North American cohort group, it is suggested that patients may be at long term risk of developing squamous cell carcinoma after as little as 120 treatments of PUVA. Those who have had more than 300 treatments have 83 times the risk of developing squamous cell carcinomas which can be multiple and metastasising. Some patients are particularly susceptible, due to other risk factors (e.g. exposure to concomitant methotrexate, ionising radiation or arsenic). This suggests that long-term follow up of high dose PUVA patients is important. Although maintenance PUVA therapy is not recommended, and has been associated with the development of squamous cell carcinoma, informed patients may choose to continue with this approach if no safer alternative treatment exists. Some evidence suggests that Melanoma incidence may increased many years after PUVA therapy, although the North American study was not consistent with the experience in Northern Europe.
Synergy with other treatments
As with UVB, adjunctive therapy using vitamin D analogue preparations, and retinoids, have been shown to be effective and are worth considering if PUVA monotherapy is inadequate.
Operation of phototherapy services
· A senior clinician, usually a consultant, with adequate training and a continuing interest in phototherapy and/or photochemotherapy should supervise the service
· An individual patient's course of therapy should be supervised by an adequately trained person (e.g. a doctor, nurse or physiotherapist)
· All phototherapy equipment should be adequately maintained and regularly calibrated by adequately trained personnel
· Accurate records of the dosage and number of treatments, for each patient, must be maintained
· Neither UVB nor PUVA should be used as permanent maintenance therapy unless alternative topical therapies have proved ineffective
References
Diffey, B.L. Factors affecting the choice of a ceiling on the number of exposures with TL01 ultraviolet B phototherapy.
British Journal of Dermatology 149 (2), 428-430.
Guidelines for dosimetry and calibration in ultraviolet radiation therapy: a report of a British Photodermatology Group workshop www.bad.org.uk/guidelines
Weischer M, Blum A, Eberhard F, Rocken M, Berneburg M.No evidence for increased skin cancer risk in psoriasis patients treated with broadband or narrowband UVB phototherapy: a first retrospective study.Acta Derm Venereol. 2004;84(5):370-4.
British Photodermatology Group. British Photodermatology Group Guidelines for PUVA. Br Med J 1994; 130: 246-55.
Lindelof B, Sigurgeirsson B, Tegner E, Larko O, Johannesson A, Berne B, Ljunggren B, Andersson T, Molin L, Nylander-Lundqvist E, Emtestam L. PUVA and cancer risk: the Swedish follow-up study Br J Dermatol. 1999 Jul;141(1):108-12
Stern RS, Nichols KT, Vakeva LH. Malignant melanoma in patients treated for psoriasis with methoxsalen (psoralen) and ultraviolet A radiation (PUVA). The PUVA Follow-Up Study.N Engl J Med. 1997 Apr 10;336(15):1041-5.
Systematic therapies for psoriasis
For an excellent evidence based review of systemic therapy see Griffiths CE, Clark CM, Chalmers RJ, Li Wan Po A, Williams HC. A systematic review of treatments for severe psoriasis. Health Technol Assess. 2000;4(40):1-125
Indications for Systematic Therapy
- Failure of adequate trial of topical therapy
- Repeated hospital admissions for topical therapy
- Extensive chronic plaque psoriasis in the elderly or infirm
- Generalised pustular or erythrodermic psoriasis
- Severe psoriatic arthropathy
- Patients considered for systemic therapy will usually conform to the rule of tens whereby the body surface area affected is greater than 10%, or the PASI score is greater than 10 or the DLQI is greater than 10.
This information forms part of the current BAD guidance document for the general management of psoriasis. Other sections in the document comprise:
