Topical tacrolimus has a limited direct effect on ultraviolet B-irradiated keratinocytes: implications for its photocarcinogenic potential

The long-term risk of lymphoma and skin cancer did not increase after topical calcineurin inhibitor use and phototherapy in a cohort of 25,694 patients with vitiligo

BACKGROUND

Topical calcineurin inhibitors have been used to treat vitiligo, either alone or in combination with phototherapy; however, the long-term safety of these agents remains controversial.

OBJECTIVE

To investigate the risk of lymphoma and skin cancer in vitiligo patients who received topical calcineurin inhibitors or phototherapy.

METHODS

A multicenter retrospective cohort study of 25,694 vitiligo patients who received topical calcineurin inhibitors or phototherapy for 6 weeks or more between 2001 and 2019 was performed. Cumulative doses of topical calcineurin inhibitors and total phototherapy sessions were determined. Outcomes were the development of lymphoma or skin cancer after enrollment, confirmed through chart review and pathology reports.

RESULTS

During 95,203 person-years, 13 cases of lymphoma, 22 of actinic keratosis, 15 of nonmelanoma skin cancer, and 5 of melanoma were observed. The risk of lymphoma and skin cancer was not significantly increased by topical calcineurin inhibitor dose or phototherapy sessions. The interaction between the topical calcineurin inhibitors and phototherapy was not associated with an increased risk of skin cancer.

LIMITATIONS

Retrospective study, individual follow-up duration less than 4 years, and no adjustment for comorbidities and medication history. Not generalizable to other races.

CONCLUSION

The long-term risk of skin cancer or lymphoma was not associated with the use of topical calcineurin inhibitors, phototherapy, and both treatments in combination in patients with vitiligo.

Irradiance, but not fluence, plays a crucial role in UVB-induced immature pigment cell development: new insights for efficient UVB phototherapy

Light exposure modulates development of living organisms. In the field of medicine, light has frequently been used for regenerative purposes. Excimer light (308 nm) has demonstrated superior efficacy in treating vitiligo, a condition requiring development of melanoblasts and a model for studying nerve cell regeneration, as compared to narrow-band ultraviolet B (NBUVB; 311 nm). Using mouse-derived melanoblast cells to examine the pro-differentiation effects of these two light sources, we demonstrated that at equivalent fluence, excimer light induces melanoblast differentiation, while NBUVB failed to so. Mechanistically, activation of aryl hydrocarbon receptor pathway and nuclear translocation of epidermal growth factor receptor are involved in pro-differentiation effects of excimer light. Reduction in irradiance by filter abrogated the effects of excimer light in melanoblasts, even when equivalent fluence was delivered by the same light source. As ultraviolet B (UVB) irradiation is closely associated pigment cell development, future therapy employing UVB for pigmentation purposes should incorporate irradiance as a crucial specification.