Condensed low-dose total skin electron beam therapy for mycosis fungoides: an institutional retrospective review and subgroup analysis of patients with large cell transformation.

Low-dose total skin electron beam therapy (TSEBT) is an effective treatment option for mycosis fungoides (MF) with proven palliative effects and reduced toxicity. Presented is an institutional analysis of survival/response rate and quality of life for MF patients with subgroup analysis of those possessing pathologic large cell transformation (LCT). This is a single institutional retrospective review of patients with mycosis fungicides treated from 2014 to 2023 with low-dose TSEBT. All patients received 12 Gy in 6 fractions every other day with the modified Stanford technique, with boosts to shadowed sites between treatments, completed in 2 weeks. Outcomes evaluated included clinical response, duration of and time to response, patient-reported quality of life, and physician-scored disease burden. Forty-six patients were included in the study, 28 male and 18 female, with a median age 66.5 (range 32.7-90.6). Stage IB was most common at the time of TSEBT (41.3%). Median follow up was 44.5 months. The overall response rate was 91.3% (52.2% partial response, 19.6% complete and near complete response). The median duration of response was 8.2 months (range, 6.1-28.7), and the median time to best response was 3.5 months (range, 2.7-5.6). Quality of life (QOL) and disease burden continued to show significant benefit after TSEBT (p<0.001). In a subgroup analysis, 18 patients (39.1%) were found to have large cell transformation (LCT) at diagnosis. LCT was associated with higher presenting stage prior to TSEBT (p=0.016) and a better response to treatment (p=0.040). However, median duration of response was only 7.4 months in the patients with LCT vs. 39.4 months in the patients without (p=0.003). Condensed Low-dose TSEBT is a convenient treatment with favorable clinical outcomes and low toxicities in patients with mycosis fungoides. Patients with LCT may have shorter duration of treatment response. Further studies are warranted to validate this finding.