(C-225) Adverse events of treatment and characteristics of patients with multiple myeloma: a Brazilian historical cohort study

Background: Multiple myeloma (MM) is a malignant bone marrow cancer that causes systemic effects, leading to reduced overall survival. Despite its incurability, treatment aims to improve survival; however, MM therapies often result in significant adverse events, which can range from common to rare and from mild to severe. Thus, real-world studies evaluating therapy safety are crucial.

Objectives: To describe newly diagnosed patients undergoing MM treatment and the associated adverse events.

Methods: This retrospective cohort evaluated MM patients treated at a public hospital in Belo Horizonte, Brazil, from 2018 to 2022. Medical records were reviewed to collect baseline data (age, sex, and international staging system - ISS, comorbidities, and treatment regimens) and adverse events (peripheral neuropathy, thromboembolic events, cardiotoxicity, and hematological events - neutropenia, leukopenia, thrombocytopenia) over a follow-up period ≥24 months. Adverse events were classified according to CTCAE v6.0, and descriptive statistics were used to characterize the patients.

Results: The study included 106 patients (mean age: 64 years; 57.5% male). Of these, 27.4%, 27.4%, 38.7% were in ISS I, II and III, respectively (6.6% were not staged). Adverse events included peripheral neuropathy (50.0%), thromboembolism (5.7%, with 4 cases of deep vein thrombosis and 2 of pulmonary embolism), and cardiotoxicity (12.3%). Hematological toxicities were neutropenia (40.6%), leukopenia (63.2%), and thrombocytopenia (70.8%). Approximately, 30% of patients started therapy from 2018 to 2020, while 70% began treatment between 2021 and 2023. During follow-up, 78 patients (44.6%) were treated with bortezomib-based regimens, and 97 patients (55.4%) received thalidomide-based therapies. A total of 34 (32.0%) patients received autologous stem cell transplantation, and (20) 18.9% died during follow-up.

Conclusions: The burden of adverse events to MM therapy is high, emphasizing the need for careful monitoring to achieve better patient outcomes. These adverse events are commonly associated with MM therapies, particularly proteasome inhibitors (bortezomib) and immunomodulators (thalidomide). Cardiotoxicity, although not a common adverse event, is emerging as an important adverse event associated with proteasome inhibitors.