Prospective Observational Trial of Low-Dose Skin Electron Beam Therapy in Mycosis Fungoides Using a Rotational Technique.

e22077 Background: Low dose total skin electron therapy (TSET) utilizing 12 Gy in 12 fractions has been shown to provide a durable treatment response for dermal lesions caused by mycosis fungoides secondary to cutaneous T cell lymphoma (CTCL). We sought to prospectively assess the durability of response and quality of life (QOL) for patients receiving low dose TSET using the rotational technique technique. Methods: We prospectively enrolled patients with CTCL on an IRB approved study from 2016 to 2019 who had pathologically confirmed CTCL from stage IB-III. Patients completed a baseline validated Skindex-29 survey encompassing 29 questions assessing QOL. Physicians graded the appearance of the skin using the modified severity-weighted assessment tool (mSWAT) at baseline. Patients received 12 Gy in 12 Fractions on consecutive dates and patients were treated with a dual field rotational technique. The mSWAT was reassessed on ensuing follow-up visits along with the Skindex. The primary outcome was overall response rate with the secondary outcomes being time to treatment response, duration of clinical benefit (time to requiring an additional intervention), as well as improvements in Skindex questionnaire items. Results: We enrolled 20 patients and recorded an overall response rate (ORR) of 90% with four complete responses. The time to treatment response was 9.7 weeks. While the baseline mSWAT was 55.6 it declined to a median mSWAT of 2.2 at last follow-up (p < 0.001) with there being a median decline of nearly 97% in the scores. The median duration of clinical benefit was 15.7 months. There was a precipitous decline in the Skindex total score and every subdomain when comparing each follow-up visit (p = 0.004) with post-hoc analysis demonstrating the decline between the baseline visit and first follow-up as the primary driver of the decline (p < 0.0001). Conclusions: This prospective study demonstrates the subjective and objective clinical benefits of utilizing low dose TSE with a dual beam rotational technique. This control rates and QOL will continue to be observed for ongoing feasibility as a treatment modality.