An assessment of the effect of photochemotherapy (PUVA) and UV-B phototherapy in the treatment of psoriasis

Half-side comparison of erythemogenic versus suberythemogenic UVA doses in oral photochemotherapy of psoriasis

BACKGROUND

Early American and European multicenter trials on the efficacy of photochemotherapy (PUVA) for psoriasis have clearly shown that the treatment protocol has a crucial impact on the cumulative UVA dose required for clearing patients. Most, if not all, treatment protocols rely on the PUVA-induced erythema as a guideline for UVA dosimetry.

OBJECTIVE

Our aim was to investigate whether phototoxic erythema is integral to an optimized PUVA protocol or reflects an unnecessary overexposure of patients.

METHODS

A standard high-dose UVA regimen using minimal phototoxic doses (MPD) was compared against two different low-dose regimens. To this purpose a bilateral comparison study was performed on 31 patients and divided in two parts. In the first trial on 14 patients, half of each patient's body was irradiated at each visit with 1 MPD, whereas the other half received only two thirds of the MPD. In the second trial on 17 patients treatment with 1 MPD was compared against treatment with one half of the MPD.

RESULTS

A total of 27 patients (12 patients in the first trial, 15 patients in the second trial) completed the study. In both trials the suberythemogenic doses were therapeutically as effective as the minimal phototoxic doses.

CONCLUSION

We conclude that PUVA-induced erythema is not a prerequisite for effective psoriasis treatment and that a low-dose UVA regimen is a promising approach to increase the short- and long-term safety of photochemotherapy.

Development of cutaneous tolerance to ultraviolet B during ultraviolet B phototherapy for psoriasis

During a schedule of multiple exposures to ultraviolet B radiation (UVB, 280-320 nm), skin develops a reduced sensitivity, variously called tolerance, photoadaptation, accommodation or acclimatization. In this study we have investigated the development of tolerance in the normal skin of a group of psoriatic patients during the course of UVB therapy. Tolerance was assessed by phototests carried out on non-lesional skin as frequently as possible throughout the treatment. Maximum tolerance was developed by the group of individuals most sensitive to UVB, which was twice that of the least sensitive group. The minimal perceptible erythema dose (MPE) increased rapidly in the first 2 weeks (220% per week) and reached a plateau by the eighth week of 800% above the baseline MPE dose. For the more sensitive patients there was a further increase in sensitivity (decrease in MPE dose) after the ninth week of continuous treatment. Tolerance to UVB also involves pigmentation in the first few weeks, but in these patients there was no evidence of hyperpigmentation by the end of treatment. While epidermal hyperplasia is most likely to play a leading role in the development of tolerance to UV, there is no reason to expect this protection to decrease under conditions of continuous exposure. Thus, accommodation to ultraviolet radiation (UVR) is not a monotonically increasing process but appears to alter the accepted reactions of human skin to UVR.

The phototumorigenic potential of broad-band (270-350 nm) and narrow-band (311-313 nm) phototherapy sources cannot be predicted by their edematogenic potential in hairless mouse skin

The new Philips TL01 narrow-band (311-313 nm) and conventional broad-band (e.g., Philips TL12; 270-350 nm) sources are effective for psoriasis phototherapy, for which treatment regimens are based on a predetermined minimal erythema dose. TL01 phototherapy treatment times are approximately half those with TL12 for psoriasis, whereas the cumulative exposure doses at clearing are similar. We compared the phototumorigenic potential of TL01 and TL12 radiation in mouse skin. Groups of albino Skh-1 hairless mice were exposed for 5 d/week at three dose levels. At each dose level, TL12 and TL01 doses were equally edematogenic. At each dose level, TL01 radiation was significantly more effective at producing first tumors of 1 mm in diameter and multiple tumors. At the lower two dose levels, TL01 radiation produced a significantly greater proportion of squamous cell carcinomas. This study demonstrates that TL01 radiation is more phototumorigenic than TL12 radiation at equally edematogenically weighted doses. This is in contrast with previous reports that edema production by polychromatic sources is predictive of their phototumorigenic effect in Skh-1 mice. The absolute cumulative TL12 dose needed to induce tumors was much less than that for TL01 radiation. The possibility of increased tumor risk with TL01 phototherapy should be considered but must be balanced against the high phototherapeutic efficacy of this source, short treatment times, and the low cumulative doses necessary for clearing of psoriasis.

A trial of accelerated PUVA in psoriasis

Ten psoriatic patients were treated with an accelerated PUVA regimen. Nine patients cleared in an average of 13.7 treatments (range 4-24) after an average total UVA dose of 83 J/cm2 (range 18-186). One patient had to withdraw due to pruritus and burning and six others had burning problems. The high incidence of burning may limit the routine use of this irradiation regimen.

Inhibitory effect of 8-methoxypsoralen plus ultraviolet-A on interleukin-1 production by murine keratinocytes

We report the effects of 8-methoxypsoralen (8-MOP) plus ultraviolet-A (UV-A) irradiation on interleukin-1 (IL-1) production by murine epidermal keratinocytes, correlating its effect on IL-1 with cell viability, DNA synthesis, and 8-MOP-DNA photoadduct formation. Freshly isolated murine keratinocytes were treated with various doses of 8-MOP (5-100 ng/mL; incubation time, 30 min) plus 1 J/cm2 UV-A and cultured for 1-3 days. The IL-1/epidermal cell-derived thymocyte-activating factor (ETAF) activity in both supernatant and cell extract was reduced proportionately with increasing doses of 8-MOP/UV-A. Interleukin-1 inhibitors induced by 8-MOP plus UV-A were not detected in either supernatant or cell extract. A clear reduction of the IL-1 production was induced by the treatment as low as 15 ng/mL 8-MOP plus 1 J/cm2 UV-A, which led to the formation of 0.52 8-MOP photoadducts per million DNa bases and affected neither cell viability nor DNA synthesis of the treated cells. Cells treated with 100 ng/mL 8-MOP and 1 J/cm2 UV-A exhibited 57% suppression of IL-1 production in both 2- and 3-day culture samples. This treatment resulted in the formation of 3.8 photoadducts per million bases as well as significant abrogation of DNA synthesis although cell viability was unchanged. These observations provide some insights into the phototoxicity mechanisms of 8-MOP and the effect of PUVA therapy on the cytokine regulation in keratinocytes.

311 nm UVB phototherapy--an effective treatment for psoriasis

Fifty two psoriatic patients were treated with a new experimental fluorescent lamp (Philips TL-01) emitting a narrow band at 311 +/- 2 nm (UVB) which had the advantage of a reduction in burning and carcinogenic wavelengths when compared with conventional broad band UVB therapy. Results of the '311' treated group when compared with broad band UVB therapy revealed a similar percentage of patients achieving a satisfactory response with fewer burning episodes and an increase in duration of remission.

UVB phototherapy and photochemotherapy (PUVA) in the treatment of polymorphic light eruption and solar urticaria

Forty subjects (36 with polymorphic light eruption and four with solar urticaria) were treated during the spring and early summer of the years 1982 to 1985 with either UVB phototherapy (a total of 54 treatment courses in subjects with polymorphic light eruption) or photochemotherapy (PUVA) (18 treatment courses in polymorphic light eruption and eight in solar urticaria patients). Both forms of prophylactic therapy were found to be effective in 90% of those with polymorphic light eruption, and PUVA in all those with solar urticaria. The optimum duration of treatment was 5 weeks. Adverse reactions, although common, were usually slight and rarely required alteration of the treatment regimen.

Psoralens and related compounds in the treatment of psoriasis

PUVA therapy has radically altered the management of severe psoriasis. It is of greatest benefit in those patients with extensive involvement, and in those unresponsive to conventional therapy. The long term side effects of PUVA currently limit its use to patients with disabling disease. The full extent of long term side effects has yet to be defined. In order to reduce the toxicity and improve the efficacy of PUVA, a better understanding of the molecular aspects of psoralen-DNA interaction, DNA repair, and mutagenesis is required. The action spectrum of PUVA in clearing psoriasis has yet to be defined. By limiting the spectrum of UVA exposure it may be possible to reduce some of the toxic effects of PUVA. The recent advances in the formulation of 8-MOP preparations has yielded a drug with more predictable pharmacokinetics and clinical response. Further research with newer psoralens may produce more effective and less toxic compounds. In the last ten years, PUVA has been both a valuable addition to dermatologists' clinical armamentarium and a useful tool in increasing our understanding of cellular biology and the interaction between ultraviolet radiation and biologic systems.

Long-term use of psoralens and ultraviolet A for psoriasis: evidence for efficacy and cost savings

A 7.3-year prospective study of 1,380 patients with psoriasis who were treated with oral methoxsalen (8-methoxypsoralen) and ultraviolet A photochemotherapy (PUVA) revealed that patients who continued on PUVA therapy used inpatient hospital treatment less than one fourth as often as those who had discontinued treatment. Patients who continued to use PUVA therapy also had less extensive psoriasis than did other patients in this cohort who discontinued PUVA therapy. These findings demonstrate that PUVA is an effective outpatient therapy for severe psoriasis. The potential toxicity of PUVA treatment, which was the primary reason that one third of the study patients were concerned about their prolonged or continued treatment, must be balanced against the therapy's apparent effectiveness and relatively low cost.

UVB maintenance phototherapy in psoriasis

Twenty-six patients with generalized stable plaque-type psoriasis were treated three to five times weekly with midwave fluorescent ultraviolet radiation (UVB) combined with either tar or lubricants. After clearing, patients received maintenance treatment with lubricant and UVB for a minimum of four weekly exposures, which were subsequently decreased in frequency. A shielded control site was observed. During maintenance treatments no prolongation in remissions with UVB maintenance could be demonstrated.

Application of controlled high dose rates in UV-B phototherapy for psoriasis

The use of a cabin fitted with Sylvania UV-21 tubes, which have a very high output of UV-B radiation, made it possible to treat psoriasis patients with a maximal exposure time of 5 minutes per session. An exposure-control unit was used to measure and regulate the applied dose to prevent overdosage. The clinical results obtained with two comparable groups of psoriasis patients treated with Sylvania UV-6 or UV-21 tubes were equal.

Tanning, protection against sunburn and vitamin D formation with a UV-A 'sun-bed'

There are many types of sun-beds, sun-benches and sun-panels containing fluorescent tubes which, because of their predominantly UV-A emission, are advertised to the public as a means of obtaining a tan without sunburn. This study reports the effects of a sun-bed on skin colour, on the protection afforded against sunburn, and on vitamin D formation. Side-effects are also recorded. It was shown that the sun-bed emits mainly UV-A but very little UV-B and some tanning occurred in most subjects. However, no correlation was observed between the subjects' stated ability to tan and the degree of pigmentation achieved at the end of the treatment. Most subjects also had itching and erythema, and three had polymorphic light eruption. Although very little UV-B irradiation was present, a significant increase in serum levels of 25-hydroxyvitamin D occurred, and possible explanations of this surprising finding are discussed. While the sun-bed proved popular with the subjects, only a modest tan was achieved and the incidence of side-effects appeared to limit the value of this type of appliance, especially with regard to the prevention of vitamin D deficiency.