Phototherapy-induced elevation of serum level of melanoma inhibitory activity.

BACKGROUND: Phototherapy is a frequently used treatment modality for a variety of dermatologic diseases. UV radiation has different effects on the skin, for example increased production and release of cytokines and other proteins, and is involved in the initiation and progression of skin cancer. Objective of this clinical trial was to investigate potential systemic effects of UV phototherapy on cytokine profiles in blood. METHODS: In a prospective, mono-centric, one-armed study, the serum levels of the melanoma tumour marker "melanoma inhibitory activity" (MIA), Il-1α, Il-4, Il-6, Il-10, TNF-α and IFN-γ of 115 patients with different skin diseases were compared before and 24-48 hours as well as 2-4 weeks after the first phototherapy with PUVA (psoralen and ultraviolet A), UVA or UVB, or both. Data were analysed using linear mixed models. RESULTS: Estimated marginal means of MIA levels were 6.05 ng/mL (95%-CI: 5.37-6.72, range: 2.83-14.49) before the first treatment, which had significantly increased to 6.79 ng/mL 2-4 weeks after the first phototherapy (CI 95%: 6.12-7.47, range: 3.09-15.45; P = 0.0042). MIA levels 2-4 weeks after the first phototherapy were significantly higher than 24-48 hours after the first phototherapy (P = 0.0083). 2-4 weeks after the first treatment, TNF-α levels had decreased significantly (P = 0.033) more in patients with psoriasis who had responded well to phototherapy than in patients unresponsive to treatment. Serum levels of the other cytokines had not changed significantly. CONCLUSIONS: Short-term phototherapy significantly increased the serum levels of the melanoma tumour marker MIA. The potential clinical relevance of these findings (ie an increased risk of melanoma) is unclear and should be further investigated.