The Value of Adjuvant Radiotherapy in the Treatment of Melanoma: A Multi-Center Analysis.

Background: Adjuvant radiotherapy (RT) may improve in-field regional tumor control in melanoma following resection of lymph node macrometastases. However, no significant effect on recurrence-free survival or overall survival has been demonstrated. The approval of adjuvant systemic immune checkpoint inhibitors and targeted therapies has significantly impacted the role of adjuvant RT. Its use in clinical practice has decreased, with heterogeneous treatment indications and approaches observed across institutions and regions. Objectives: The aim of the present study was to characterize the population of melanoma patients still undergoing adjuvant RT in the era of modern adjuvant systemic treatments, and to outline potential clinical scenarios in which it may continue to play a role in the future. Patients and methods: Fifty-eight patients treated with adjuvant RT were identified in five participating Austrian and Swiss dermato-oncologic centers. Treatment timing, toxicity, recurrence patterns, and survival outcomes were analyzed, and compared to 88 stage-matched, non-irradiated patients from a German cohort of patients who met formal RT criteria. Results: The majority of irradiated patients (53.5%) received RT before systemic therapy. The concurrent administration of adjuvant systemic therapy and radiotherapy did not increase the frequency of RT-associated toxicities (77.8% vs. 74.2%, p = 0.456). No significant differences in recurrence-free survival or overall survival were observed between irradiated and non-irradiated patients (p = 0.725 and p = 0.986, respectively). Conclusions: Although still recommended in certain melanoma guidelines, adjuvant RT is infrequently performed in the era of modern systemic treatments. Due to its exclusively locoregional efficacy, the application of adjuvant RT should be limited to clearly defined scenarios where systemic treatment options are limited and locoregional control is most important. The concurrent administration of adjuvant RT and systemic therapy is safe and should be preferred if a combined treatment strategy is chosen.