Comparison of Low-Dose and Standard-Dose Total Skin Electron Beam Therapy for Mycosis Fungoides

Abstract

Total skin electron beam therapy (TSEBT) is one of the most effective treatments for mycosis fungoides (MF). Though historically treated to 30-36 Gy, recent studies have established 12 Gy as an effective dose. This low-dose regimen has been recommended as the standard treatment. Our institution has been treating MF patients with 12Gy in the last 2 years. We intended to compare response rates and time to progression and time to retreatment of standard-dose TSEBT and low-dose TSEBT. Patients with Stage IB – IVA MF receiving TSEBT at our institution between 2010 and 2016 were included in our retrospective analysis. Nine patients received a total of 10 courses of low-dose TSEBT to 12 Gy. One of these patients received a second repeat course of TSEBT during this time. Ten patients received standard-dose TSEBT between 30-36 Gy. All patients experienced at least a partial response to treatment. Two of the 10 courses of low-dose TSEBT resulted in a complete response compared to 7 of the 10 patients receiving standard-dose TSEBT (20% vs. 70%, p = 0.070). The average time to progression for low-dose TSEBT was 3.09 months and for standard dose TSEBT was 10.22 months (p = 0.021). Three patients receiving low-dose TSEBT and four patients receiving high-dose TSEBT underwent additional radiation, with the average time to an additional course of radiation being 3.1 months for low dose TSEBT and 10.1 months for standard dose TSEBT (p = 0.23). One patient receiving low-dose TSEBT also underwent a second course after 3.8 months. Standard-dose TSEBT was associated with increased toxicity, with most patients experiencing some degree of skin irritation. Three patients had dry desquamation, one developed bullae of the feet, and one patient had skin numbness. Only one patient in the low-dose TSEBT group had dry desquamation, and skin dryness was the predominant side effect. Median follow-up was 17.9 months. Low-dose TSEBT was associated with a significantly lower complete response rate and time to progression compared to standard-dose TSEBT. Benefits of this regimen include the ability to retreat with TSEBT and a lower toxicity profile.