Ultra-hypofractionated low-dose total skin electron beam in advanced stage mycosis fungoides and Sézary syndrome.

PURPOSE: To assess the safety and efficacy of ultra-hypofractionated low-dose total skin electron beam therapy (TSEBT) regimen in patients with advanced mycosis fungoides (MF) or Sézary syndrome (SS).

PATIENTS AND METHODS: In this multicenter observational study from five German centers, 18 total patients with MF/SS underwent TSEBT with a total dose of 8 Gy in two fractions. The primary endpoint was the overall response rate (ORR).

RESULTS: 15 of 18 patients with stage IIB-IV MF or SS were heavily pre-treated with a median of four prior systemic therapies. The ORR was 88.9% (95%-confidence interval (CI): 65.3-98.6), with three complete responses (17%). At a median follow-up period of thirteen months, the median time to next treatment (TTNT) was 12 months (95%-CI: 8.2-15.8), and the median progression-free survival was 8 months (95%-CI: 2-14). A significant reduction in the modified severity-weighted assessment tool (mSWAT), total Skindex-29 score (Bonferroni-corrected P-value < 0.005), and all subdomains (Bonferroni-corrected P-values < 0.05) was observed after TSEBT. Half of the irradiated patients (N=9) developed grade 2 acute and subacute toxicities. One patient had confirmed grade 3 acute toxicity. Chronic grade 1 toxicity has been observed in 33% of patients. Patients with erythroderma/SS or prior radiation therapy appear at higher risk of skin toxicities.

CONCLUSION: TSEBT with 8 Gy in 2 fractions achieves good disease control and symptom palliation with acceptable toxicity, greater convenience, and fewer hospital visits.