Abstracts Clinical Lymphoma, Myeloma & Leukemia September 2023 S464 T-Cell Lymphoma TCL-054 A Multi‑Institutional Prospective Cohort Study of Minimal Residual Disease in Peripheral T‑Cell Lymphoma: Impact of Autologous Stem Cell Transplant (ASCT) Nicole Foley MD1, David Russler-Germain MD, PhD1, Marcus Watkins PhD1, Eric Jacobsen MD2, Alison Moskowitz MD3, Amanda Cashen MD1, Todd Fehniger MD1, Brad Kahl MD1, Nancy Bartlett MD1, Armin Ghobadi MD1, Beth Reagan1, Anne Fischer1, Fei Wan PhD1, Austin Jacobsen4, Karina Elias4, Matt Holman4, Natalie Hill4, Skylar Gordon4, Ying Huang PhD4, Steven Horwitz MD3, Neha Mehta-Shah MD1 1Washington University School of Medicine, St. Louis, USA. 2DanaFarber Cancer Institute, Boston, USA. 3Memorial Sloan Kettering Cancer Center, New York, USA. 4Invivoscribe, Inc., San Diego, USA Background: Roughly 80% of patients with peripheral T-cell lymphomas (PTCL) respond to CHOP-based therapy, but 5-year survival ranges between 20% and 40%. Given high rates of relapse after complete response (CR), minimal residual disease (MRD) testing may have prognostic value. Next-generation sequencing (NGS) of the T-cell receptor (TCR) can detect a known TCR clonotype at 10-5. In a prospective study, we evaluated MRD testing via TCR NGS in PTCL (NCT03297697). Here we report results for patients pre- and post-ASCT. Methods: Eligible patients had previously untreated PTCL not otherwise specified (NOS), angioimmunoblastic T-cell lymphoma (AITL), anaplastic large cell lymphoma (ALCL), PTCL with T-follicular helper (TFH) phenotype, or monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) treated with anthracycline-based curativeintent therapy. Baseline TCR (TRG or TRB) clonotypes were established from diagnostic tissue or peripheral blood. TCR clonality was determined positive via LymphoTrack® TRG/TRB Assays – MiSeq® (Invivoscribe, San Diego, CA) when top % reads were ≥2.5% and ≥2x above background. Samples were obtained at diagnosis (pre-treatment), following induction therapy (pre-ASCT), and serially post-ASCT. Results: Of 43 enrolled patients, 19 underwent consolidative ASCT, of which 10 had post-ASCT samples available for MRD testing. Median age at ASCT was 62 years (range: 38-77). At pre-ASCT evaluation, 7/10 patients had detectable TCR MRD (“positive”) and 3/10 patients had TCR MRD below the level of detection (“negative”). Of the 3 MRD-negative patients pre-ASCT, 2 had CR and 1 had PR by PET-CT. All 7 TCR MRD-positive patients pre-ASCT had CR by PET-CT. Of 7 MRD-positive patients pre-ASCT, 6 remained MRD-positive and 1 became MRDnegative post-ASCT. Of the 4 MRD-negative patients post-ASCT, none have relapsed at 52, 31, 34, and 31 months post-ASCT. Of 7 MRD-positive patients pre-ASCT, 3 have relapsed following ASCT (at 3, 9, and 29 months post-ASCT). Conclusions: In this cohort of PTCL patients receiving consolidative ASCT in CR1, all 4 patients with negative TCR MRD post-ASCT remain in remission at median follow-up of 32.5 months. The negative predictive value of TCR NGS MRD post-ASCT warrants further evaluation. Keywords: TCL, PTCL, peripheral T-cell lymphoma, minimal residual disease, ASCT, autologous stem cell transplant, T-cell receptor, nextgeneration sequencing TCL-060 Mogamulizumab‑Associated Rash in Patients With Mycosis Fungoides and Sézary Syndrome Nicole Foley MD, Chelsea Minor PharmD, Amy Musiek MD, Neha Mehta-Shah MD Washington University School of Medicine, St. Louis, USA Introduction: Mycosis fungoides (MF) and Sézary syndrome (SS) are the most common forms of cutaneous T-cell lymphoma (CTCL). Mogamulizumab (mogam) is a monoclonal antibody against CCR4 approved for use in CTCL in 2018. In its registration study, mogamulizumab-associated rash (MAR) affected 24% of patients; clinically, we have observed MAR more commonly. Objective: To describe MAR in a real-world setting/understand causes and treatment for it. Methods: We retrospective analyzed all patients with CTCL treated consecutively with standard mogam at Washington University from 2018-2022; patients included were diagnosed with MF/SS, having received ≥1 dose of mogam. Results: Twenty patients with CTCL (7 MF, 13 SS) were identified: median age 69 (range 42-78) years (9 males). Median number of systemic therapies prior to mogam was 1 (range 0-15). Of 20 patients who received mogam, 12 developed biopsy-confirmed MAR (60%) that developed after median of 10.5 (range 5-22) doses or 4 (range 1-10) months of mogam treatment. Development of MAR led to discontinuation of mogam in 10/12 patients. Treatment strategies and associated responses included: topical steroids (10/12 patients; 4/10 responded), short-course prednisone (5/12 patients; 4/5 responded), oral methotrexate (3/12 patients; 1/3 responded), oral bexarotene (4/12 patients; 2/4 responded), phototherapy (1/12 patients; 1/1 responded), oral cyclophosphamide (1/12 patients; 1/1 responded), JAK2 inhibitor (1/12 patients; 1/1 responded). Rash median duration was 43 (range 4-138) weeks. Five of 12 patients with MAR were retreated later; all 5 redeveloped rash. Clinical response (objective response rate) of CTCL to mogam was 75% (15/20); 6 achieved a global complete response (CR). Of 6 patients with global CR, 5 developed rash. Thirteen patients had baseline blood involvement (B1/B2), of which 69% (9/13) achieved blood CR. Of 9 patients with blood CR, 7 developed rash (77%). Of 6 people who achieved global CR, 4 sustained a CR without any subsequent treatment at 2.1 (range 1.3-2.9) years of follow-up. Conclusions: The frequency and persistence of MAR in clinical practice appears greater than previously described. Given the high efficacy and response durability to mogam, understanding precipitating factors and effective treatments for MAR is critical to better application of mogam for patients with CTCL. Keywords: mycosis fungoides, Sezary syndrome, cutaneous T-cell lymphoma, mogamulizumab, mogamulizumab-associated rash
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