CD25 expression could be a prognostic marker of bexarotene monotherapy for cutaneous T‐cell lymphomas

Bexarotene is often administered to phototherapy‐resistant early cutaneous T‐cell lymphoma (CTCL) patients as one of the first‐line therapies in real‐world practice. Since bexarotene reduces the expression of CCR4 in CTCL cells and CCL22 to decrease serum CCL22 levels, bexarotene inhibits the migration of CTCL cells, as well as other CCR4+ cells, such as cytotoxic T cells and regulatory T cells, in the lesional skin of CTCL. In this report, the efficacy of bexarotene in 28 cases of CTCL, as well as its correlations with immunohistochemical profiles of tumour‐infiltrating leucocytes (TILs), was retrospectively investigated. The overall response rate at 1 and 4 months for the total cohort was 70.8% (95% CI, 50.6%–86.3%) and 47.8% (95% CI, 29.2%–67.0%), respectively. The disease control rate for the total cohort at 4 months was 65.2% (95% CI, 44.8%–81.3%). The mean event‐free survival for all patients was 4.1 months (0.3–68.5 months). In addition, the immunoreactive cells were calculated using digital microscopy, suggesting that the ratio of CD25+ cells among TILs was significantly increased in patients who responded to bexarotene (p = 0.0209), whereas there were no significant differences in the ratios of CD8+ cells, granulysin+ cells, and Foxp3+ cells among TILs between responder and non‐responder patients. Collectively, the ratio of CD25 expression among TILs might be a predictive biomarker for the efficacy of bexarotene.