Promising Responses, Improved Skin-Related QoL Observed With Low-Dose Skin Electron Beam Therapy for Mycosis Fungoides

Low-dose rotational total skin electron beam therapy produced a high overall response rate (ORR) and improved skin-related quality of life (QoL) when used to treat patients with skin manifestations of mycosis fungoides, according to research from a prospective study published in the Journal of the American Academy of Dermatology.

The ORR for the patient population was 90%, with 11 patients experiencing at least a 97% reduction in Modified Severity-Weighted Assessment Tool scores from baseline. Investigators reported a partial response rate of 60%, a complete response rate of 20%, and a stable disease rate of 10%. Although the baseline Modified Severity-Weighted Assessment Tool score was 55.6, it declined to a median of 2.2 as of the last follow-up (P < .001).

“In this study, we present prospective clinical outcomes for patients with extensive skin manifestations of mycosis fungoides treated with low-dose rotational total skin electron beam therapy to 12 Gy,” the investigators wrote. “To our knowledge, we are the first to demonstrate the clinical utility of this approach, using a dual-field rotational technique with a fractionation scheme of 1 Gy per day consecutively, via both objective and subjective metrics.”

Twenty patients enrolled on the study and were included in the interim analysis, which took place after a median follow-up of 512 days. Patients had a median age of 61.5 years. In terms of previous treatments, 10 patients received prior systemic therapy, 10 received electron radiotherapy therapy, and 9 received phototherapy. Following treatment with low-dose total skin electron beam therapy, the median time to objective response was 6.5 weeks.

Eligible patients were 18 years of age or older with skin manifestations of mycosis fungoides who were refractory to or relapsed on prior therapies. Patients were assessed with the Modified Severity-Weighted Assessment Tool, as well as the patient-completed Skindex-29 questionnaire. Patients were treated with 1200 cGy in 12 fractions with a 6-MeV electron beam delivered via a dual-field technique.

The study’s primary end point was changes in clinical response due to changes in the Modified Severity-Weighted Assessment Tool score. Key secondary end points included ORR, time to treatment response, duration of clinical benefit, and changes in responses for the Skindex-29 questionnaire.

Most patients began maintenance therapy after initial therapy, with different maintenance options including bexarotene (Targretin; n = 10), ultraviolet-based therapy (n = 3), immunotherapy (n = 1), and topical agents (n = 12).

The Skindex-29 QoL baseline analysis identified a median value of 93.5 for the total score, as well as 23.5, 29.5, and 14 for the symptomatic, emotional, and physical subdomains, respectively. At the first follow-up point (approximately 6 weeks following completion of total skin electron beam therapy), the median total score decreased significantly to 63.5 (P < .001).

The small cohort of patients who were treated at a single institution was considered to be a major limitation of the research, according to the investigative team. The short median follow-up also is concerning, and the results warrant longer follow-up to better understand how patients fare in the long term.

“Our study adds to the increasing body of literature suggesting low-dose total skin electron beam therapy regimens may be the preferred initial treatment strategy for patients with widespread skin manifestations of mycosis fungoides. Further follow-up and accrual of patients to this ongoing study are planned,” the investigators concluded.

Reference

Newman NB, Patel CG, Ding GX, et al. Prospective observational trial of low-dose skin electron beam therapy in mycosis fungoides using a rotational technique. J Am Acad Dermatol. 2021;85(1):121-127. doi:10.1016/j.jaad.2020.12.023