Brentuximab Vedotin in CutAneous T-cell Lymphomas (CTCL): Post-allogeneic Hematopoietic Stem Cell Transplant Maintenance

Inclusion Criteria: To be eligible for study entry, patients must meet all of the following criteria: * Age ≥ 18 and ≤ 70 years * Histopathologically confirmed diagnosis of ISCL-EORTC stage IIB, III, IVA or IVB MF (mycosis fungoides) with ≥1% CD30 expression determined by immunohistochemistry * ECOG performance status 0-1 * Relapsed or refractory to at least one line of systemic treatment * Complete or partial response of the lymphoma at the time of study inclusion * Having received recent alloHSCT from a sibling, 10/10 or 9/10 phenoidentical, or haploidentical donor (60 to 90 days before inclusion) * Adequate liver function: * Total bilirubin ≤ 2 xULN, or Direct bilirubin ≤ 2xULN if total bilirubin is \>2xULN, or total bilirubin \>2 xULN if elevated total bilirubin is attributed to Gilbert's syndrome * Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 3 x ULN * Adequate hematological function: * Absolute neutrophil count of ≥ 1.0 G/L * Platelet count of ≥ 50 G/L * Hemoglobin ≥ 9 g/dL * Adequate renal function: creatinine clearance calculated by Cockcroft \& Gault formula of ≥ 50 mL/min * Patient affiliated to life insurance * Written informed consent given by the patient Exclusion Criteria: Any of the following criteria requires the exclusion of the patient before randomization: * Second or higher allogeneic HSCT, * Other progressive neoplastic or psychotic disease, * Left ventricular ejection fraction \< 50%, carbone monoxide diffusion capacity \< 50% of the theoretical value, * History of BV-induced adverse event without resolution to current grade \<2. Previous treatment with brentuximab vedotin alone, in the absence of current ≥ grade 2 BV-induced side effect, is NOT an exclusion criterion. * History of disease refractoriness, progression or relapse during BV treatment. Previous treatment with BV alone, if the disease was treatment-sensitive (complete, partial response or stable disease), is NOT an exclusion criterion. * History of ≥ grade 4 adverse event induced by BV. Previous \<grade 4 adverse event induced by BV is not an exclusion criterion if the adverse event has regressed to grade\<2. * Contra-indication to BV including current \>grade 2 neutropenia or active infection, * Progressive disease or relapse at study inclusion compared to the screening visit status, * Refusal of highly effective birth control method for female participant of childbearing potential and male participant with a female partner of childbearing potential, * Pregnant and/or breastfeeding women, * Participation to another interventional clinical trial, * Adults subject to a legal protection measure (guardianship, curatorship and safeguard of justice), * Patients deprived of their liberty by a judicial or administrative decision