Merkel cell carcinoma: long-term outcomes after radiotherapy treatment

Background Merkel cell carcinoma (MCC) is a rare, aggressive disease with high relapse and fatality rates. Radiotherapy (RT) is essential for local control, but published data on both initial treatment and relapse management remain limited. Material and methods We retrospectively analyzed 17 patients treated in a single-center with radical and adjuvant RT. Results After a mean follow-up of 44 months, five (29%) patients relapsed (mean time to relapse 5.8 months after RT). Four relapses were locoregional, occurring outside the RT field, and received local salvatge therapy. One relapse was distant. Three patients received up to three consecutive RT courses for locoregional progression without systemic therapy. Five (29%) patients died after a mean time of 35.2 months, four of them with active disease. Two deaths were due to disease progression. Conclusions Despite optimal local treatment, relapse remains common and is linked to poor outcomes, such as distant progression and death. Our findings reinforce the need for close postoperative monitoring and early initiation of adjuvant RT. Outcomes after early relapse suggest a potential role for treatment intensification.