Toxicity-Related Treatment Cessation in Newly Diagnosed Multiple Myeloma-Risk Factors and Survival: An Analysis From the APAC and ANZ Myeloma and Related Diseases Registry.

BACKGROUND: Toxicity-related treatment cessation (TTC) limits optimal outcomes in newly diagnosed multiple myeloma (NDMM), but its determinants and prognostic relevance remain unclear. METHODS: A total of 3095 NDMM patients were enrolled between 2018 and 2024 in the Asia-Pacific and Australia-New Zealand Myeloma and Related Diseases Registries. Baseline features, treatments, and outcomes were analyzed to identify predictors of TTC and assess its association with progression-free survival (PFS) and overall survival (OS). RESULTS: TTC occurred in 9% of patients. Advanced age and renal function were independent predictors in multivariable logistic regression, whereas comorbidity burden was not significant after adjustment. Proteasome inhibitor exposure was associated with lower odds of TTC, while immunomodulatory drug use was not independently associated. Patients with TTC had inferior unadjusted survival (median PFS 22.1 vs. 34.4 months; median OS 53.8 vs. 70.8 months; both p < 0.001). In adjusted analyses, TTC was not associated with PFS or OS; however, in age-stratified analyses, TTC remained associated with shorter PFS in patients aged < 70 years (adjusted HR 1.44, p = 0.03), with no significant association observed in patients ≥ 70 years. CONCLUSION: TTC may reflect physiologic vulnerability and retains prognostic relevance in younger patients. It may serve as a practical marker to complement frailty assessment in NDMM.