Abstracts Clinical Lymphoma, Myeloma & Leukemia September 2023 S492 MM-348 Fluorescence in situ Hybridization (FISH) t(11;14) Testing Practices Over Time in Patients With Newly Diagnosed Multiple Myeloma (MM) in the USA in the Flatiron Health Database Linda B. Baughn PhD1, Sophia Li MPH2, Rongrong Wang MPH2, Faiza Zafar MPAS2, Archibong Yellow-Duke PharmD2, Vivek S. Chopra PhD2, Allicia Girvan PhD3, Shaji K. Kumar MD1 1Mayo Clinic, Rochester, MN, USA. 2Genentech Inc., South San Francisco, CA, USA. 3AbbVie, Inc., North Chicago, IL, USA Context: t(11;14) is an important biomarker of MM prognosis and response to therapy, including the BCL-2 inhibitor venetoclax. As MM management evolves with emerging targeted therapies and risk-stratification measures, FISH testing for t(11;14) is needed. We assessed USA testing practices in MM to understand biomarker testing trends and equitable practices using the Flatiron Health database. Design and Setting: This retrospective study included patients aged ≥18 years, diagnosed with MM as their first and only malignancy in the nationwide Flatiron Health electronic health-record derived, deidentified database, between January 2011 and July 2022, with ≥2 clinic encounters 6 months after diagnosis. Clinical trial participants were excluded. FISH testing rates at diagnosis (≤30 days prior to or 90 days post-diagnosis) were evaluated across 3 timeframes: start of study to R-ISS publication (January 2011–August 2015), R-ISS to updated National Comprehensive Cancer Network (NCCN) guidelines which include venetoclax for t(11;14)+ MM (September 2015–May 2020), and updated NCCN guidelines to end of study (June 2020–July 2022). Time to FISH from diagnosis was assessed. Results: Among 12,284 eligible patients, at diagnosis, median age was 70 years, 46% were female, and 68.8% (n=8,451) had a FISH test. Testing rates at diagnosis increased yearly, from 50.1% in 2011 to 75.1% by 2022, and during the 3 defined timeframes (starting from earliest) were 60.2%, 72.1%, and 74.6% (P<0.001). For FISH tests beyond diagnosis (≤30 days prior or any time post-diagnosis), 75% had ≥1 test and median time to test was 13 days. Testing rates were similar regardless of care setting, race/ethnicity, gender, and socioeconomic status, but decreased with older age (<65 years: 80.1% [n=3,484/4,351], 65–75 years: 76.4% [n=3,123/4,088], >75 years: 66.3% [n=2,550/3,845]). All subgroups had a median time from diagnosis to test of <30 days. Despite 17.8% of tested patients having t(11;14), first treatment choice was unimpacted, with similar first-line regimens reported for patients with/without t(11;14). Conclusion: FISH testing at diagnosis has increased since 2011 alongside changes in MM management guidelines. Although the Flatiron Health database shows minimal testing disparities, other studies indicate real-world survival imbalances; there is still a need to identify and address disparities pre- and post-MM diagnosis. Keywords: MM, FISH, real-word data, t(11;14), venetoclax MM-360 Mezigdomide (MEZI) Plus Dexamethasone (DEX) in Relapsed/ refractory Multiple Myeloma (RRMM): Results From the Dose‑Expansion Phase of the CC‑92480‑MM‑001 Trial Robert Z. Orlowski MD, PhD1, Nizar J. Bahlis MD2, Hang Quach MD3, Rakesh Popat MD, PhD4, Sagar Lonial MD5, Kihyun Kim MD6, María-Victoria Mateos MD, PhD7, Charlotte Pawlyn MD, PhD8,9, Karthik Ramasamy MD, PhD10, Joaquín Martínez-Lopez MD, PhD11, Ignacio Casas-Avilés MD12, Alessia Spirlì PhD13, Jing Gong PhD14, Michael Amatangelo PhD14, Jessica Katz MD, PhD14, Paulo Maciag MD, PhD14, Teresa Peluso MD, PhD13, Paul G. Richardson MD15, Suzanne Trudel MD16 1Department of Lymphoma & Myeloma, The University of Texas MD Anderson Cancer Center, Houston, TX, USA. 2Arnie Charbonneau Cancer Institute, University of Calgary, Calgary, AB, Canada. 3St. Vincent’s Hospital Melbourne, University of Melbourne, Melbourne, VIC, Australia. 4NIHR UCLH Clinical Research Facility, University College London Hospitals NHS Foundation Trust, London, United Kingdom. 5Winship Cancer Institute, Emory University, Atlanta, GA, USA. 6Sungkyunkwan University, Samsung Medical Center, Seoul, Korea, Republic of. 7University Hospital of Salamanca/IBSAL, Salamanca, Spain. 8The Royal Marsden NHS Foundation, London, United Kingdom. 9The Institute of Cancer Research, London, United Kingdom. 10Department of Clinical Haematology, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom. 11Department of Hematology, Hospital 12 de Octubre, Complutense University, H12O-CNIO Clinical Research Unit, CIBERONC, Madrid, Spain. 12Hospital San Pedro de Alcántara, Cáceres, Spain. 13Celgene International Sàrl, a Bristol-Myers Squibb Company, Boudry, Switzerland. 14Bristol Myers Squibb, Princeton, NJ, USA. 15DanaFarber Cancer Institute, Boston, MA, USA. 16Division of Medical Oncology and Hematology, Princess Margaret Cancer Centre, University of Toronto, Toronto, ON, Canada Context: MEZI is a novel, potent oral cereblon E3 ligase modulator (CELMoD™) with enhanced antimyeloma effects compared with immunomodulatory drugs (IMiDs®). In CC-92480MM-001 phase I (NCT03374085), the recommended phase II dose (RP2D) of MEZI+DEX was 1 mg once daily for 21/28 days. Here we report results from the MEZI+DEX dose-expansion cohort in heavily pretreated RRMM. Methods: Patients had: RRMM; ≥3 prior lines of therapy; triple-class refractory disease; disease progression ≤60 days of last myeloma therapy. MEZI 1 mg was given on Days 1–21 of each 28-day cycle with 40 mg weekly DEX (20 mg >75 years). Primary objective was overall response rate (ORR); secondary objectives included safety/tolerability and additional efficacy assessments. Pharmacodynamics was an exploratory objective. Results: As of 16 Sept 2022, 101 patients had received MEZI+DEX at the RP2D. Median age was 67 (range, 42–85) years and median number of prior therapies was 6 (range, 3–15). All patients were triple-class refractory and refractory to their last regimen. Median follow-up was 7.46 (range, 0.5–21.9) months. ORR was 40.6%, median progression-free survival (mPFS) was 4.4 (95% CI: 3.0–5.5)
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