Aspirin vs. Rivaroxaban for Thromboprophylaxis in Multiple Myeloma

Inclusion Criteria: 1. Age 18 to 70 years at the time of screening. 2. Newly diagnosed multiple myeloma with measurable disease according to the Chinese Guidelines for the Diagnosis and Management of Multiple Myeloma (2020 revision). 3. Scheduled to receive immunomodulatory drug (thalidomide, lenalidomide, or pomalidomide)-based chemotherapy regimens. 4. No clinical history or imaging evidence of venous thromboembolism at the time of initial diagnosis. 5. Life expectancy \> 3 months. 6. Adequate renal function defined as an endogenous creatinine clearance (CrCl) ≥30mL/min calculated by the Cockcroft-Gault formula. 7. Absence of active systemic infectious disease requiring intravenous antimicrobial therapy. 8. Female patients of childbearing potential must have a documented negative serum pregnancy test at screening. Male and female patients of reproductive potential must agree to use highly effective contraception methods throughout treatment and for at least 3 months following the final dose. 9. Ability to understand the study procedures, comply with protocol follow-up visits, and voluntarily provide written informed consent signed by the patient or a legally authorized representative. Exclusion Criteria: 1. Active hepatitis B virus (HBV) infection, active hepatitis C virus (HCV) infection, or other known acquired/congenital immunodeficiency syndromes. 2. Baseline peripheral neuropathy or neuropathic pain ≥ Grade 2 according to NCI CTCAE version 5.0. 3. Diagnosis of plasma cell leukemia. 4. History of severe or recurrent venous/arterial thromboembolism prior to study enrollment. 5. History of clinically significant or severe bleeding manifestations within 6 months prior to enrollment. 6. Clinically significant or unstable cardiovascular diseases, including: Symptomatic myocardial ischemia or acute coronary syndrome; Uncontrolled, clinically significant cardiac arrhythmias (excluding stable, treated arrhythmias, isolated first-degree AV block, or asymptomatic bundle branch block); Congestive heart failure classified as New York Heart Association (NYHA) Class ≥ III, or known left ventricular ejection fraction (LVEF) \< 40%; Myocardial infarction within 3 months prior to Cycle 1 Day 1 (C1D1). 7. Impaired hepatic function: ALT and/or AST ≥ 2.0 ✖️ upper limit of normal (ULN); or total bilirubin ≥1.5 ✖️ ULN. 8. Severe renal impairment with CrCl \< 30mL/min or requiring renal replacement therapy. 9. Concurrent malignancy requiring active therapy or evidence of disease recurrence within 5 years prior to randomization (excluding adequately resected non-melanoma skin cancer or successfully treated cervical carcinoma in situ). 10. Major surgery within 30 days prior to study enrollment. 11. History of epilepsy, dementia, or severe psychiatric disorders that impair the patient's capacity to understand or comply with the protocol requirements. 12. Severe physical, psychiatric, or substance abuse disorder that, in the opinion of the investigator, may interfere with study participation, adherence, or outcome assessments. 13. Concurrent participation in another investigational therapeutic clinical trial. 14. Pregnant or breastfeeding women. 15. Any other medical condition, lab abnormality, or circumstance that, in the investigator's judgment, renders the participant unsuitable for enrollment.