UVA1 Phototherapy in a national reference center:A 10-year systematical analysis

UV A1 phototherapy (340-400 nm) has proven safe and effective for various skin conditions. However, limited published data make it challenging to establish individualized treatment protocols for many of these disorders. This study retrospectively analyzed the efficacy and tolerability of medium-dose UV A1 phototherapy (40-60 J/cm²) for various dermatological conditions.

We performed a single-center retrospective analysis of 249 patients with different dermatoses treated with UVA1 phototherapy between 2010 and 2019 at the Department of Dermatology, University Hospital Zurich. Treatment response was classified as complete, partial, or no response, based on clinical examination, scores, photographic documentation and standardized questionnaires. Patients primarily received medium-dose UV A1 therapy three times weekly. Adverse events were graded according to CTCAE v5.0. All patients were followed up for at least two years.

The most common indications were sclerosing dermatoses (39.8%), atopic dermatitis (32.5%), and granuloma annulare (14.9%). The mean single dose was 49.25 J/cm², administered three times weekly, with a mean cumulative dose of 1395.32 J/cm². Overall, 78.3% of patients showed objective clinical improvement, with 14.9% achieving a complete response and 63.5% a partial response. Objective response rates did not differ significantly between diagnostic groups (p = .169). Subjective improvement was reported by 65.9% of patients. Mild adverse events (CTCAE grade I), primarily transient erythema and UV-induced hyperpigmentation, occurred in 26.5% of patients. One patient experienced a moderate adverse event (second-degree burn), and no serious adverse events occurred.

Predominantly medium-dose UVA1 phototherapy was associated with a high overall clinical response rate across the main diagnostic groups, with predominantly mild and transient adverse events. These findings support UVA1 phototherapy as an effective treatment option for selected inflammatory and sclerosing dermatoses. Further studies should investigate long-term safety, maintenance protocols, patient-specific factors, and combination therapies.