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.

Keywords: Administrative claims; Cancer; Medicare; Mortality; Population-based cohort; Proxy for performance status.