Mortality by a proxy performance status as defined by a claims-based measure for disability status in older patients with newly diagnosed multiple myeloma in the United States.

ABSTRACT

OBJECTIVES: We applied a claims-based definition of disability status as a proxy for performance status (PS) and examined associations between PS and mortality in a population-based cohort of older US adults with multiple myeloma (MM). MATERIALS AND METHODS: We identified older (≥66 years) Medicare beneficiaries diagnosed with MM January 1, 2008-December 31, 2011, who began first-line therapy in the study period (through December 31, 2012). We estimated predicted probability of poor PS for each patient at initiation of each line up to fourth-line therapy, classified as poor (predicted probability ≥0.11) or good (<0.11) PS, and examined mortality. Crude overall survival was estimated using the Kaplan-Meier method with log-rank test for survival comparison between PS groups. Cox proportional hazards models evaluated the association between poor PS and mortality risk, adjusted for baseline characteristics by lines of therapy. RESULTS: Of 12,547 patients, 5841, 2372, and 819 initiated second-, third-, and fourth-line in the study period. Poor PS proportions were 16.6%, 21.8%, 18.4%, and 18.2% at each line. Crude overall survival was worse for poor PS patients across lines (P < 0.01 for each). Adjusted hazards ratios (95% CI) of mortality for patients with poor versus good PS were 1.28 (1.18-1.40), first-line; 1.55 (1.36-1.77), second-line; 1.35 (1.10-1.65), third-line; 1.22 (0.84-1.76), fourth-line. CONCLUSION: The claims-based prediction model for disability status performed as expected as a proxy for PS in older Medicare patients with MM. PS was an independent risk factor for mortality. Further studies assessing the effect of PS on mortality by therapies are warranted.