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Risk of squamous cell carcinoma and methoxsalen (psoralen) and UV-A radiation (PUVA). A meta-analysis.

OBJECTIVE
To assess the risk of squamous cell carcinoma (SCC) and the relation of dose to risk among groups of patients with psoriasis exposed to psoralen-UV-A (PUVA).


DATA SOURCES
Four electronic databases were searched from 1984 to 1998.


STUDY SELECTION
In addition to the PUVA Follow-up Study, we included all English-language studies from the United States and Europe with at least 150 patients enrolled, who were followed up for at least 5 years as identified from our bibliographic search.


DATA EXTRACTION
A custom-designed questionnaire was used to extract data from each of the articles. For each study, if possible, we determined the incidence of basal cell carcinomas and SCCs and the incidence rate ratio of SCC among patients exposed to low-dose (we defined as < 100 treatments or 1000 J/cm2) compared with high-dose PUVA (> 200 treatments or 2000 J/cm2). Exact methods were used to calculate the incidence rate ratios.


DATA SYNTHESIS
In addition to our study, we identified and reviewed 8 other studies. Overall, the incidence among patients exposed to high-dose PUVA was 14-fold higher than among patients with low-dose exposure (95% confidence interval, 8.3-24.1); a greater dose-dependent increase in risk than that observed in the PUVA Follow-up Study.


CONCLUSION
Although the incidence of SCC reported among groups of PUVA-treated patients followed up for at least 5 years varies greatly, compared with the risk in low-dose patients, long-term high-dose exposure to PUVA was consistently observed to significantly increase the risk of SCC in all studies reviewed.