P-348: Time to treatment initiation among Black and White older adults with multiple myeloma: A SEER-Medicare analysis

Introduction:
Timely treatment initiation after diagnosis has been identified as an important component of quality cancer care. This study aims to describe time to treatment initiation for Black and White older adults with newly diagnosed multiple myeloma (MM), and to test the hypothesis that as treatments have become more effective over time, Black/White treatment initiation disparities will have increased.

Methods:
Black and White adults diagnosed with MM (2007-2017) were identified in the SEER-Medicare database. Individuals were required to have continuous Medicare Parts A and B 12 months before and after diagnosis (or until death), Part D 12 months after diagnosis (or until death) and not be enrolled in an HMO.

We explored time to treatment initiation by race across three diagnosis time periods (2007-10, 11-14, 15-17) using Cox proportional hazard models to estimate hazard ratios with 95% confidence limits(CL), adjusted for age and sex using inverse probability weighting, accounting for death as a competing risk. We further estimated cumulative incidence of treatment initiation by race, at 3, 6 and 12 months after diagnosis across our three time periods.

Results:
White MM patients had a higher likelihood of initiating treatment than Black MM patients across all time periods. Hazard ratios (HR), varied only slightly over time, ranging from 1.35(CL = 1.25, 1.46) in 2007-10 to 1.36(1.27, 1.44) for those diagnosed 2015-17.



Estimates of cumulative incidence show an increasing proportion of Black and White MM patients initiating treatment over time. For example, the proportion(CL) of Black MM patients initiating treatment within 12 months increased from 0.43(0.39, 0.49) in 2007-10 to 0.58(0.53, 0.62) in 2015-17. Cumulative incidence of White MM patients initiating treatment within 12 months increased from 0.54(0.51, 0.56) in 2007-10 to 0.69(0.67, 0.70) in 2015-17.



Amidst increased treatment initiation for both Black and White patients, we found White MM patients were significantly more likely to initiate treatment than Black MM patients for all treatment initiation windows and diagnosis time periods. Differences in proportions of Black and White MM patients initiating treatments were consistent (ranging from 0.9(0.02, 0.15) to 0.11(0.05, 0.17) across treatment initiation windows and time periods. These data suggest that Black/White disparities are not changing over time.

Conclusions: We report substantial, entrenched Black/White disparities in MM treatment initiation. Our results show that newly diagnosed Black MM patients are more likely to initiate treatment later than White patients and further that Black MM patients are less likely than White patients to ever receive MM treatment. Contrary to our hypothesis, Black/White disparities are not increasing over time, remaining substantial and unchanging. Further studies are needed to gain a deeper understanding of the multilevel determinants of these entrenched disparities among older newly diagnosed MM patients.