Impact of Race/Ethnicity on Cancer Associated Thrombosis Among Underserved Patients with Cancer

Introduction: Cancer-associated thrombosis (CAT) is common among patients with cancer. Risk factors for CAT include type of malignancy, advanced stage, and chemotherapy treatment, but the association of CAT with race and ethnicity remains controversial. Identifying the incidence of CAT among populations susceptible to inequalities in healthcare delivery may help delineate preventive strategies. Methods: We performed a retrospective cohort study at Harris Health System (HHS), a safety-net healthcare system that provides care for underserved minorities and uninsured patients in Houston, TX. We created an integrated database that linked consecutive patients with newly diagnosed invasive cancer with structured electronic health record (EHR) data from 2011-2020 (Figure 1). We followed patients from time of cancer diagnosis to time of first VTE, death, or loss of follow-up. VTE was defined as radiologically confirmed pulmonary embolism (PE), lower extremity deep vein thrombosis (LE-DVT), catheter-related DVT (CR-DVT), or splanchnic vein thrombosis in either inpatient or outpatient setting. We used VTE ICD9/ICD10 billing codes to assess for potential events and confirmed incident, recurrent, and historical events through medical record review. VTE occurring within 30 days prior to cancer diagnosis were considered as CAT at diagnosis. Incidence rates were assessed per 100 person-year (py) within 1 year of diagnosis and stratified by race/ethnicity, cancer type, and cancer stage. Cumulative incidence of VTE was assessed through competing risk method with death as the competing cause. Multivariable Fine-Gray competing risk models were performed to determine the effect of race/ethnicity on the risk of CAT, adjusted for age, sex, body mass index, insurance, cancer site, stage, systemic therapy, recent hospitalization, and prior history of VTE. Results: A total of 9,353 cancer patients were included in the study, where 49.3% were Hispanics, 27.6% were Non-Hispanic Blacks (NHB), 15.5% were Non-Hispanic Whites (NHW), and 7.6% were Asian/Pacific Islander (PI). Most patients (74.7%) were uninsured, 35.8% were obese, 19% had recent hospitalization, and 31.9% had stage IV disease. Overall, 832 developed CAT within 1 year, including 49.4% PE, 28.1% LE-DVT, and 17.1% CR-DVT. The median onset was 69 days (IQR 20-154), but a significant proportion (n=92) was diagnosed in the month before diagnosis. The incidence of CAT was 7.3% at 6 months and 9.6% at 1 year. The overall inciden