Advanced cutaneous T-cell lymphoma (CTCL) has several biologic and targeted options, but comparative evidence is limited, responses differ between skin, blood, and lymph nodes, and the optimal sequence is not established.
New international recommendations from 30 experts address this by tying treatment to stage, to the compartments involved, and to early identification of patients who may benefit from allogeneic hematopoietic cell transplantation. The European Hematology Association, the EORTC Cutaneous Lymphoma Tumours Group, the International Society for Cutaneous Lymphoma, and the Lymphoma Working Party of the European Society for Blood and Marrow Transplantation developed them jointly.
Prognosis and Risk Assessment
Mycosis fungoides (MF) and Sézary syndrome (SS) are the most common forms of CTCL. MF typically begins with patches or plaques and may progress to tumors, erythroderma, or extracutaneous disease. SS combines erythroderma, substantial circulating malignant T-cell involvement, and an identical T-cell clone in skin and blood.
Early-stage MF is often indolent, but advanced disease is not. Observational data show a median overall survival of about five years for stages IIB-IVA1, and below three years with extensive nodal or visceral disease.
The recommendations adopt the Cutaneous Lymphoma International Prognostic Index, which counts four adverse features: age above 60 years, elevated lactate dehydrogenase, large-cell transformation in the skin, and N3 lymph node involvement. Five-year overall survival is 63.3% with 0-1 factors, 44.7% with two, and 18.3% with three or four. The score can inform treatment intensity and the timing of transplant evaluation.
Diagnostic Work-Up: Every Compartment
Staging uses the TNMB system (skin, lymph nodes, viscera, blood). Skin assessment should record body surface area involved and, preferably, the modified Severity-Weighted Assessment Tool score, with histopathology by a dermatopathologist experienced in CTCL. In suspected advanced disease, biopsy is paired with immunophenotyping and T-cell receptor clonality testing, and comparing skin and blood clones is key when SS is suspected.
Peripheral blood flow cytometry is required in tumor-stage or erythrodermic disease, with a minimum panel of CD3, CD4, CD7, CD8, CD26, and CD45. PET-CT is preferred for nodal and visceral assessment, and suspicious nodes should have excisional or adequate core biopsy. Routine bone marrow biopsy is not recommended without unexplained hematologic abnormalities or another indication.
Progression should trigger reassessment of every compartment. New tumors, erythroderma, lymphadenopathy, or lesions that behave differently from the rest of the disease may indicate large-cell transformation or a change in biology.
First-Line Treatment of Advanced MF
Most patients receive immunomodulatory and biologic therapy, with conventional chemotherapy reserved for selected aggressive presentations. Choice depends on the extent and type of skin involvement, blood and nodal disease, prior therapy, comorbidities, and transplant eligibility.
Interferon, Retinoids, and Methotrexate
Pegylated interferon-α and systemic retinoids remain first-line options, often with skin-directed treatment. Bexarotene is given alone or with phototherapy, extracorporeal photopheresis, or interferon, and requires proactive management of hypertriglyceridemia and central hypothyroidism, usually with lipid-lowering drugs and thyroid hormone replacement.
Pegylated interferon-α2a can be used alone or combined with bexarotene, phototherapy, or low-dose methotrexate. Combinations may raise response rates, but comparative evidence is limited. Weekly low-dose methotrexate remains accessible, particularly in erythrodermic MF and older patients, and its manageable toxicity suits prolonged treatment. These options are preferred when disease control doesn’t require intensive cytotoxic therapy.
Radiotherapy
Radiotherapy is integral for localized tumors and extensive symptomatic skin disease. In stage IIB MF with few tumors, localized low-dose radiotherapy (about 8-12 Gy) gives one-year local control above 90%. Total skin electron beam irradiation (TSEBI) is effective in widespread tumors or erythroderma, and low- or intermediate-dose regimens are favored for tolerability and to preserve the option of retreatment. Relapse after TSEBI is common, so it is usually combined with systemic therapy or used in preparation for allo-HCT.
Chemotherapy
Single-agent gemcitabine or pegylated liposomal doxorubicin and multiagent regimens such as CHOP are discouraged as routine first-line treatment. Observational evidence associates chemotherapy-based approaches with inferior survival, and toxicity is high while response durability is limited. Chemotherapy remains appropriate for rapidly progressive tumors, extensive lymphomatous nodal involvement, or the need for rapid disease reduction before transplantation. Single agents are preferred unless aggressive disease requires more.
Relapsed or Refractory MF: Brentuximab Vedotin vs Mogamulizumab
Both agents are central after at least one prior systemic therapy, but their roles differ.
Brentuximab vedotin, an anti-CD30 antibody-drug conjugate, is most relevant in stage IIB MF and in large-cell transformation. The phase III ALCANZA trial established efficacy in previously treated CD30-expressing CTCL. Responses can occur with low CD30 expression, though eligibility follows regulatory requirements. Peripheral neuropathy is the main treatment-limiting toxicity, may require dose reduction, longer intervals, or discontinuation, and doesn’t always resolve.
Mogamulizumab, an anti-CCR4 antibody, is most effective against circulating malignant T cells. Activity is greater in blood and skin than in lymph nodes, so patients may have excellent blood responses while retaining or developing nodal disease, and nodal status needs continued clinical and radiologic assessment.
Mogamulizumab-associated rash can resemble active MF or SS, so biopsy is needed when the distinction is unclear. In observational studies, the rash has been associated with better outcomes. Prior mogamulizumab exposure may also increase the risk of severe graft-versus-host disease after transplantation, which affects planning.
In practice, brentuximab vedotin suits CD30-expressing tumor-stage or transformed MF, and mogamulizumab suits disease with prominent blood involvement.
Sézary Syndrome: First Line ECP
Substantial blood involvement makes SS a different problem from tumor-stage MF. ECP is a cornerstone of first-line therapy, especially with erythroderma and circulating Sézary cells. Published overall response rates are about 54%-77%, with responses developing gradually and blood improving before skin. Its tolerability and limited systemic immunosuppression support prolonged use in patients already prone to infection.
ECP is commonly combined with bexarotene, pegylated interferon-α, or low-dose methotrexate, chosen by blood tumor burden, erythroderma, symptoms, and tolerance of additional therapy. Retrospective studies suggest earlier ECP-containing treatment may prolong time to next treatment and improve survival, but this has not been tested in randomized comparisons.
Second Line: Mogamulizumab
Mogamulizumab is the preferred second-line treatment after progression. In the randomized phase III MAVORIC trial, it improved median PFS over vorinostat from 3.1 to 7.7 months, with the greatest benefit in patients with substantial blood involvement. Real-world data support its use: the OMEGA registry reported an ORR of about 70%, and PROCLIPI observational data linked mogamulizumab to improved survival in selected SS patients. Blood flow cytometry every three months is recommended to monitor response and detect recurrence.
Brentuximab vedotin evidence in SS is weaker because these patients were excluded from ALCANZA. In multiply relapsed disease, alternatives include gemcitabine, pegylated liposomal doxorubicin, histone deacetylase inhibitors, pralatrexate, and alemtuzumab. Alemtuzumab may work in leukemic disease but carries substantial risks of prolonged immunosuppression and opportunistic infection, so strict prophylaxis and monitoring are required.
Combination and Maintenance Strategies
Combinations are widely used to address disease in several compartments. In stage IIB MF, common approaches pair phototherapy with bexarotene or interferon, sometimes with localized radiotherapy. In erythrodermic MF and SS, ECP-based combinations are most relevant. Mogamulizumab with ECP is used in practice, and mogamulizumab with TSEBI is being evaluated prospectively. Several common combinations lack strong comparative evidence.
Maintenance is individualized: ECP, interferon, bexarotene, and methotrexate may be continued or adjusted after disease control, and intervals may be extended in selected mogamulizumab-treated patients. In the phase III RESMAIN trial, resminostat maintenance improved median PFS from 4.2 to 8.3 months over placebo. The European Medicines Agency nevertheless refused marketing authorization in May 2025, concluding that the benefit-risk balance was unfavorable.
Allogeneic Transplantation: Refer Early in High-Risk Disease
Allo-HCT is the only potentially curative treatment for advanced MF and SS, and its effect depends largely on graft-versus-lymphoma activity, in which donor immune cells eliminate residual malignant T cells. It should be considered in eligible patients with advanced or high-risk disease:
- large-cell transformation
- N3 nodal involvement
- visceral disease
- elevated lactate dehydrogenase
- relapse after systemic therapy
Referral should occur early, ideally when first systemic therapy is planned in a potentially eligible high-risk patient. It doesn’t mean every patient with advanced MF or SS should proceed straight to transplant.
Disease Control Before Transplant
Transplantation is favored in complete or very good partial remission, ideally with substantial clearance of skin and nodal disease. Limited residual blood involvement can be compatible with success because of the graft-versus-lymphoma effect. Transplantation during uncontrolled, rapidly progressive disease is discouraged. Bridging may use brentuximab vedotin, mogamulizumab, TSEBI, or chemotherapy in selected transformed disease.
Mogamulizumab Washout
CCR4-targeted treatment can deplete regulatory T cells and increase the risk of severe acute GVHD, so an interval is advised between the last mogamulizumab dose and transplant. An interval of at least six weeks between the last mogamulizumab dose and transplant is advised, and two to four months is preferred when clinically feasible. For patients with a realistic transplant plan, the longer interval should guide sequencing when disease control allows. Checkpoint inhibitors may also raise GVHD risk, and a washout of at least six weeks is recommended.
Conditioning and Outcomes
Reduced-intensity conditioning is generally preferred because it preserves graft-versus-lymphoma activity and lowers toxicity. Historical nonrelapse mortality was about 15%-20%, and more recent series report about 10%. Relapse remains a major limitation, occurring in up to half of transplanted patients in some series, but durable complete remissions are achievable.
Posttransplant relapse is often confined to skin and may respond to skin-directed therapy, withdrawal of immunosuppression, donor lymphocyte infusion, or interferon-based treatment. These responses are clinical evidence of ongoing graft-versus-lymphoma activity, to be balanced against GVHD risk.
Emerging Therapies
Lacutamab targets KIR3DL2, which is expressed in a large proportion of SS patients. In the TELLOMAK study, the overall response rate in relapsed or refractory SS was 42.9%, with a median response duration of 25.6 months. Activity after prior mogamulizumab addresses a major unmet need, but use is restricted to clinical trials.
CTX-130 is an investigational allogeneic CD70-directed CAR T-cell therapy produced with CRISPR-Cas9 gene editing. In the phase I COBALT-LYM study, ten patients had CTCL, and the response rate in this subgroup was 40%, including one complete response. The cohort is too small to judge durability or define a role, and cytopenias, infections, and cytokine release syndrome are safety concerns.
The recommendations also review agents targeting JAK/STAT, PI3K, EZH2, CCR8, CD47, CD74, and CDK9, most in early development with limited CTCL-specific evidence. Denileukin diftitox-cxdl received US FDA approval in 2024 for relapsed or refractory stage I-III CTCL after prior systemic therapy. In its single-arm pivotal study, the overall response rate was 36.2% and median response duration 8.9 months, and capillary leak syndrome is an important risk.
Supportive Care and Follow-Up
Symptoms and complications need continuous management even when systemic disease is controlled. Pruritus is among the most burdensome symptoms and can severely affect sleep, daily function, and psychological well-being, so routine assessment and individualized skin-directed and systemic antipruritic treatment are encouraged.
Ulcerated tumors and widespread barrier disruption raise infection risk, and wound care, infection surveillance, and prompt antibacterial treatment are essential. Staphylococcus aureus colonization deserves attention because it may cause inflammation and treatment resistance in malignant T cells.
Follow-up should also cover treatment toxicity, secondary malignancies, progression in previously uninvolved compartments, and quality of life, coordinated across dermatology, hematology, pathology, radiation oncology, and transplantation teams.
Reference: Onida F, Quaglino P, Scarisbrick J, Sureda A, Hodak E, Papadavid E, et al. Management of advanced mycosis fungoides and Sézary Syndrome: International Recommendations for systemic treatments and allogeneic hematopoietic cell transplantation from the European Hematology Association, the EORTC Cutaneous Lymphoma Tumours Group, the International Society for Cutaneous Lymphoma, and the Lymphoma Working Party of the EBMT. HemaSphere. Published November 5, 2026. DOI: 10.1002/hem3.70505.
