Prognostic Frailty-Based Determinants of Long-Term Mortality in Older Patients with Newly Diagnosed Multiple Myeloma

Background/Objectives: Multiple myeloma (MM) is a plasma cell neoplasm predominantly diagnosed in older adults. However, the significance of defining patient frailty, as well as identifying the most suitable and reliable tools for its assessment, remains to be firmly established. Methods: This retrospective observational study investigated 36 patients aged 65 or older who underwent Comprehensive Geriatric Assessment (CGA). The average patient age was 76 (SD 6.22), with 33.3% being female. Patients were evaluated using the International Myeloma Working Group Frailty Index (IMWG-FI) and the 40-item Rockwood’s Frailty Index (FI) at the Oncogeriatrics clinic of the IRCCS Polyclinic San Martino Hospital, Genoa, Italy between December 2017 and August 2021. Laboratory, cancer-specific, demographic, and clinical variables were collected. Survival analysis and frailty comparison were conducted using Stata version 17.0. Results: Stepwise multivariate analysis identified the Numerical Rating Scale (NRS) (HR 1.40, 95% CI 1.09–1.78, p = 0.008) and Rockwood’s Frailty Index (FI) (HR 2.23, 95% CI 1.29–3.87, p = 0.004) as significant prognostic predictors, adjusted for sex, ISS stage, and multimorbility. Comparison between Rockwood’s FI and IMWG-FI using Spearman correlation coefficient showed no statistically significant correlation (r = 0.268, p = 0.114). Multivariate Cox model, adjusting for sex, International Staging System (ISS) stage, and Cumulative Illness Rating Scale (CIRS) comorbidity index demonstrated the superior predictive ability of Rockwood’s FI over IMWG-FI (C-index 0.775 vs. 0.749). Conclusions: The 40-item Rockwood FI emerges as a valuable tool for prognostication in old MM patients, demonstrating non-inferiority to the traditional IMWG-FI in predictive accuracy, emphasizing the importance of a comprehensive approach considering both disease-specific and patient-related factors.