Disease characteristics, prognosis, and response to therapy in patients with large-cell transformed mycosis fungoides: A single-center retrospective study

Background: Mycosis fungoides with large-cell transformation (MF-LCT) is associated with an aggressive clinical course, yet data comparing treatment outcomes in MF-LCT are sparse.

Objective: To compare treatment outcomes and to determine disease prevalence and characteristics associated with survival in MF-LCT.

Methods: A retrospective review was conducted of mycosis fungoides patients from 2012 to 2020 treated at Thomas Jefferson University. Patients with histopathologic diagnosis of MF-LCT were included. Treatment outcomes were assessed by mean changes in the modified Severity Weighted Assessment Tool (mSWAT) and stage.

Results: Of 171 patients with mycosis fungoides, 23 (13.4%) had histologic diagnosis of MF-LCT. The overall 5-year survival rate for MF-LCT was 74% and was not significantly associated with sex, age, or initial stage at the time of MF-LCT diagnosis. Brentuximab vedotin showed the greatest mean decrease in mSWAT (-20.53) and stage progression (change in Δ stage: -0.4) in MF-LCT compared to oral bexarotene (ΔmSWAT: +4.51; Δstage: +0.27), skin-directed therapy (ΔmSWAT: -5.93; Δstage: -0.08), and chemotherapy (ΔmSWAT: +4.97; Δstage: +0.85).

Limitations: Single-center retrospective design, and patients often on multiple treatment modalities.

Conclusions: We report superior treatment outcomes for brentuximab vedotin compared to oral bexarotene, skin-directed therapy, and chemotherapy in MF-LCT in both early and advanced disease.