Pb2158: relapsing/refractory abdominal wall extra-medullary plasmacytomas demonstrating a rapid complete response to belantamab mafodotin

Topic: 14. Myeloma and other monoclonal gammopathies - Clinical Background: A 71-year-old male was diagnosed in November 2018 with Symptomatic Multiple Myeloma. Baseline investigations showed IgG Kappa para-protein of 31 g/L, FISH analysis failed as bone marrow plasma cells <10%. CT PET scan showed a large sternal mass 9x9.7x7 cm, SUV max. of 7.6 with left 8th rib lesion, SUV max of 7.8. He received standard RVD (Revlimid, Velcade and Dexamethasone) regimen for 7 cycles with very good partial response (VGPR). Paraprotein decreased to 3g/l however there was only slight reduction in plasmacytoma size to 9x8.5x4 with SUV max 7.3. He was switched to KRD (Carfilzomib, Revlimid and Dexamethasone) along with radiotherapy to the sternal lesions with very good response biochemically (SPEP, normal pattern) and radiologically (repeat CT PET scan showed no metabolically active disease with no residual mass). He proceeded to ASCT in March 2020.High risk maintenance was commenced with Lenalidomide + Velcade, however, after 4 months he showed radiological relapse. The treatment was switched to DVD (Daratumumab, Velcade and Dexamethasone) with very good partial response. In July 2021, he noticed multiple small lesions about 0.5-1 cm on the abdominal wall. Biopsy confirmed clonal plasma cells in the abdominal wall subcutaneous fat. The lesions were resolved with local radiotherapy. Aims:Methods: In October 2021 shortly after COVID booster vaccine, the abdominal wall lesions markedly increased in size and number making a confluent group of nodules approximately 20cm x 15cm.He was commenced on Belantamab through the compassionate access program in December 2021. After completing 2 cycles, the nodules completely resolved. At the end of June 2022, he exhibited a biochemical relapse and re-imaging showed new sub centimeter Lymphadenopathy, but no recurrence of the abdominal wall lesions. Results: Our patient showed a complete response of extramedullary Myeloma to BELANTAMAB Summary/Conclusion: The extramedullary phase of Myeloma remains a major medical challenge and further studies are required to clarify the role of antibody-drug conjugates.Keywords: Plasma cells, Multiple myeloma