Transportation insecurity and RBC transfusion burden in multiple myeloma and related plasma cell disorders in New Mexico: A CRIIS statewide analysis (2013-2019).

1532 Background: Multiple myeloma (MM) and related plasma cell disorders are commonly complicated by anemia requiring red blood cell (RBC) transfusion. In geographically large and predominantly rural states such as New Mexico, transportation insecurity may contribute to fragmented outpatient access and downstream supportive care burden. Using statewide oncology informatics data, we characterized RBC transfusion utilization patterns and their association with county-level vehicle access. Methods: Using the Cancer Research Integrated Informatics System (CRIIS), a novel statewide oncology informatics platform, we identified patients with MM and related plasma cell disorders (including Waldenström macroglobulinemia and plasma cell leukemia) receiving care from 2013-2019. We performed a repeated cross-sectional county-level analysis, using county-year as the analytic unit. Transportation insecurity was defined as the percent of households without vehicle access and summarized using the median county value across 2013-2019 due to minimal year-to-year variability. Counties were categorized as higher versus lower transportation insecurity using a median split. The primary outcome was receipt of ≥1 RBC transfusion within a calendar year, summarized at the county level. Results: Among 2,436 patients statewide, 614 (25.2%) received ≥1 RBC transfusion. Annual transfusion utilization increased from 15.0% in 2013 and stabilized at ~25-30% thereafter. Median county transportation insecurity ranged from 0% to 12.8%. Across multiple years, counties with higher transportation insecurity accounted for a disproportionate share of statewide transfusion burden relative to patient volume (~1.3-1.5-fold higher absolute transfusion burden). Transfusion burden was concentrated in a subset of counties, with Bernalillo contributing the largest share, while several smaller counties demonstrated high transfusion rates despite low total patient volume. Transfusion delivery remained concentrated in access-rich counties, consistent with regional centralization of oncology supportive care. Conclusions: In this statewide real-world analysis, RBC transfusion burden in MM and related plasma cell disorders clustered disproportionately among residents of transportation-insecure counties. Transportation insecurity may serve as a pragmatic structural marker to identify regions bearing elevated supportive care burden and supports collaborative evaluation of transportation-focused care delivery strategies to improve equity across rural and underserved communities. Statewide cohort size and RBC transfusion utilization by year. Year Total Patients Transfused Patients Transfusion Rate (%) 2013 240 36 15.0 2014 238 49 20.6 2015 301 67 22.3 2016 373 109 29.2 2017 411 118 28.7 2018 427 107 25.1 2019 446 128 28.7 Total 2,436 614 25.2