Low-dose UV-therapy: effectivity and safety aspects

This thesis investigated the effectivity and safety of low-dose phototherapy in the treatment of skin diseases. The current individualised, “on demand society” creates the need for treatment in the patients’ home at a time point that suits the patient best. But little was known on safety and effectivity of low-dose UV-treatment. This thesis is comprised of three parts: 1. A review of the literature to understand what the hurdles are in prescription of phototherapy, 2. Investigating the effectivity of low-dose home-based phototherapy, 3. Investigating the potential carcinogenic risk of low-dose home based phototherapy. Conclusion and recommendations Low-dose phototherapy is an effective treatment in patients with PLE and mild to moderate psoriasis. PLE patients were more satisfied with the low-dose home based treatment than conventional treatment. Low-dose phototherapy could be given continuously and patients are less limited in planning their activities, which might improve quality of life. For psoriasis patients with mild to moderate complaints low-dose phototherapy might help patients who are tired of the frequent ointment applications or in need of an adjuvant with their corticosteroid therapies. Prolonged treatment up to 18 months appears safe, although further studies are needed to corroborate this and provide more evidence about the effects in even longer time intervals. In these studies it would be relevant to also ascertain the presence of p53 mutations in the epidermis. As skin malignancies can develop after years of chronic UV-exposure it would be wise to advocate for regular skin check-ups for patients undergoing this treatment. An electronic monitoring would be advisable to corroborate the adherence to treatment protocol, although the results of the present study suggest that there is no major reason for concern. This is in line with the results of prior studies. Dermatologists should, however, stay on their toes about development of “tanorexia” which could place a patient at risk for skin cancer. Tanorexia is reported to be caused by the release of β-endorphins by UV light. Not all patients exposed to UV-light develop tanorexia however. There probably are other factors playing a part in the development of this addiction. It is shown in this thesis that low-dose phototherapy is effective in PLE and psoriasis; it is probable that this therapy might be relevant for other inflammatory skin diseases, such as atopic dermatitis, vitiligo or graft versus host disease. Further studies to demonstrate effectiveness and safety of a home-based low-dose phototherapy in other diseases are warranted. Another interesting aspect of the low-dose home-based phototherapy is the rise in vitamin D. If low-dose phototherapy is confirmed to be safe, it would be an interesting option to use this device in patients with or at risk for hypovitaminosis D, such as dialysis patients who also often deal with uremic pruritus. Other patients that could benefit from this are elderly who are at risk for bone fractures, or patients with chronic pain associated with vitamin D deficiency. Prior studies have demonstrated that patients with hypovitaminosis D use more opiates, than patients with normal vitamin D levels. It might be interesting to investigate the effect of low-dose UV in patients with chronic pain requiring opiates with and without hypovitaminosis D. Could low-dose phototherapy lessen their pain use of opioids? And is this effect due to the stimulation of β-endorphins or is it the result of normalisation of vitamin D levels? To recapitulate: if low-dose phototherapy is confirmed to be safe in prolonged treatment, it might provide a valuable tool in the treatment not only dermatological diseases, but also various internal diseases.