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Low-dose TSEBT offers fast effective treatment in certain patients with mycosis fungoides

In patients with stage IB to IIIA mycosis fungoides, treatment with low-dose total skin electron beam therapy yielded a quick, predictable decrease in disease burden, according to recently published study findings.

In a pooled analysis, researchers collected data from three clinical trials. The first (trial A1) was an open-label, single-arm, phase 2 study comprising 15 patients that assessed the safety and efficacy of low-dose (12-Gy) total skin electron beam therapy (TSEBT). The second parallel trial (trial A2), used a similar protocol and comprised four patients. The third (trial B) consisted of 14 participants in the monotherapy arm of a multicenter, open-label, randomized, two-arm, phase 2/3 study, which evaluated the safety and efficacy of low-dose TSEBT alone vs. low-dose TSEBT in combination with Zolinza (vorinostat, Merck). The trials had identical eligibility criteria, radiation treatments, schedule of safety and efficacy assessments, and criteria for clinical response and radiation toxicity. Clinical response rate as defined by the modified severity weighted assessment tool (mSWAT) was the primary endpoint for all trials. Secondary endpoints included time to response (TTR), duration of response (DOR), and treatment safety and tolerability. The researchers also defined a new clinical endpoint, duration of clinical benefit (DOCB), which was defined as the time from initial response until the start of any total skin-equivalent treatment, systemic therapy or progressive disease. Kaplan-Meier product limit estimates were used to calculated the DOCB.

All patients were adults with biopsy-confirmed mycosis fungoides stage IB to IIIA who failed to respond to at least one previous treatment. Patients underwent baseline assessments 4 weeks or less prior to the start of treatment. TSEBT was administered at a dose of 12 Gy, fractionated at 2 Gy/cycle, during a 3-week period.

The researchers found an overall response rate of 88%, and nine patients achieved a complete response. The median TTR was 7.6 weeks, and the median DOCB was 70.7 weeks. The most significant decrease in mSWAT score was seen between weeks 4 and 8, with a median 45% reduction between these points. The maximum decrease in mSWAT score from baseline ranged from 61% to 100%, according to the researchers.

All treatment-related toxicities were found to be mild and reversible.

Disclosure: The authors have no relevant disclosures.