Comparison of the carcinogenic potential of trioxsalen bath PUVA and oral methoxsalen PUVA. A preliminary report

PUVA and cancer risk: the Swedish follow-up study

“…What could then explain the differences in the results of our study and in the report of Stern et al . ? 29 In our cohort almost one‐fifth of the patients had received bath PUVA 30 which might be less carcinogenic 37 than the oral regimen; for example, the ultraviolet A doses are 15–20 times lower. The pattern of concurrently given drugs can differ between Europe and the U.S.A., e.g.…”

British Association of Dermatologists and British Photodermatology Group guidelines for the safe and effective use of psoralen–ultraviolet A therapy 2015

“…More recently, the U.S.A. 16‐centre, follow‐up study has reported an increased incidence of melanoma in patients treated with PUVA, but it remains uncertain that this was a causative association and this association has not been reported by other groups . There is no evidence of either increased incidence of NMSC or melanoma in patients with psoriasis treated by topical PUVA . However, the number of patients with high PUVA exposure was low in these studies and many were treated with bath TMP PUVA.…”

“…265,273,281,282 There is no evidence of either increased incidence of NMSC or melanoma in patients with psoriasis treated by topical PUVA. 283,284 However, the number of patients with high PUVA exposure was low in these studies and many were treated with bath TMP PUVA. It seems likely that any differential risk of carcinogenicity relates more to differences in psoralens than different routes of administration, so it seems reasonable, on the basis of current knowledge, to believe that the risks per phototoxic exposure should be the same for oral 8-MOP PUVA as for bath 8-MOP PUVA.…”

“…However, the number of patients with high PUVA exposure was low in these studies and many were treated with bath TMP PUVA. It seems likely that any differential risk of carcinogenicity relates more to differences in psoralens than different routes of administration, so it seems reasonable, on the basis of current knowledge, to believe that the risks per phototoxic exposure should be the same for oral 8‐MOP PUVA as for bath 8‐MOP PUVA . This is a reason why the (mainly historical) use of cumulative UVA dose with PUVA when considering action limits is less useful than considering number of treatments as cumulative UVA dose will always tend to be less with topical PUVA even when the number of phototoxic exposures is the same.…”

Kinetics and dose-response of photosensitivity in cream psoralen plus ultraviolet A photochemotherapy: comparative in vivo studies after topical application of three standard preparations

“…One major concern with PUVA therapy is the potential long‐term carcinogenic risk 3,4 . In contrast to oral PUVA therapy, retrospective studies evaluating the carcinogenic risk of bath PUVA with methoxsalen and trioxsalen as photosensitizers have not so far shown an increased carcinogenic risk 24,25 . However, prospective studies with a large number of patients are still lacking and a definite answer is not yet possible.…”