Low-dose decitabine combined with camrelizumab for refractory/relapsed mycosis fungoides/Sézary syndrome: a retrospective exploratory study.

BACKGROUND: Mycosis fungoides (MF) and Sézary syndrome (SS) are the main subtypes of cutaneous T-cell lymphomas that are characterized by clinical heterogeneity and are difficult to cure. Objective: This retrospective study evaluated the efficacy and immunomodulatory effects of low-dose decitabine combined with camrelizumab, a novel PD-1 monoclonal antibody used to treat patients with refractory advanced MF/SS. METHODS: The enrolled patients received decitabine (10 mg/d, days 1-5) combined with camrelizumab (200 mg, day 7) every 4 weeks. The response was assessed and peripheral blood was analyzed for T-cell subsets, cytokines, Lactate Dehydrogenase (LDH), β2-microglobulin levels, and lymphocyte parameters. Adverse events were monitored.Results: From February 2021 to May 2025, 14 patients were enrolled in the study (3 SS, 1 folliculotropic MF, and 6 with large-cell transformation). The objective response rate was 71.4% (10/14), with 5 complete (CR) and 5 partial responses (PR). At a median of 13.5 months follow-up, 3 patients maintained sustained CR. Common adverse events were grade 1-2 leukopenia (21.4%), elevated transaminases (28.6%), and camrelizumab-related mucocutaneous capillary proliferation (50.0%). Exploratory immunophenotyping showed a progressive decline in the CD4+/CD8+ ratio, lower baseline LDH, and absolute lymphocyte counts in responders, whereas non-responders had significantly higher IL-5 and IL-13 levels (P < 0.05). CONCLUSION: The combination regimen showed encouraging preliminary activity and tolerability in this small retrospective cohort, although the efficacy of SS remains suboptimal. These findings are hypothesis-generating and require prospective validation.