Low-Dose Total Skin Electron Beam Therapy Combined With Mogamulizumab for Refractory Mycosis Fungoides and Sezary Syndrome

Purpose: Management of patients with refractory mycosis fungoides and Sezary syndrome (SS) is often challenging, as available therapies lack durable response and consistent activity across disease compartments. Combining low-dose total skin electron beam therapy (LD-TSEBT) upfront with mogamulizumab could optimize the clinical outcome of these patients. LD-TSEBT is effective in clearing skin disease, and mogamulizumab is an antitumor immunotherapy with long-term tolerability, suggesting its potential as a maintenance therapy after maximal response. We examine the combination regimen in patients with SS who were previously treated. Methods and Materials: Two patients with SS were treated with combination LD-TSEBT and mogamulizumab. Both patients received mogamulizumab 1 mg/kg weekly x 4 and then bi-weekly; LD-TSEBT (12 Gy) was initiated within 2 days of starting mogamulizumab and given over 2-3 weeks. Safety and clinical response were evaluated. Results: Total skin electron beam therapy plus mogamulizumab (TSE-Moga) was well-tolerated without any unanticipated adverse events. Patient 1 (T4N2bM0B2) was a 63-year-old woman with 4 prior systemic therapies; time to global response with TSE-Moga was 9 weeks. Patient 2 (T4NxM0B2) was a 75-year-old man with 5 prior systemic therapies; time to global response was 4 weeks. Both patients lacked global response to their prior therapies but achieved global complete response (blood and skin) with TSE-Moga. After a follow-up of 72 weeks and 43 weeks, respectively, global complete response continued. Conclusions: TSE-Moga demonstrated excellent tolerability and promising clinical activity with ongoing global complete responses in 2 patients with refractory SS. This encouraging experience supports our ongoing clinical trial evaluating the efficacy and safety of TSEMoga in mycosis fungoides and SS. (C) 2020 The Author(s). Published by Elsevier Inc. on behalf of American Society for Radiation Oncology.