Abstract
Background: Several studies have shown that cancer is associated with a 2 to 9-fold increased risk of venous thromboembolism (VTE) (Heit 2000; Hutton 2000; Hansson 2000; Prandoni 2002; Descourt 2006), with an absolute risk ranging from 1%-8% (Timp 2013). Importantly, the presence of VTE significantly reduces the 1-year survival rate from 36% in cancer patients without VTE to 12% in cancer patients with VTE (Sorensen 2000). Large cohort studies in the general population have suggested that Blacks compared to Whites are at higher risk of developing VTE (Zakai 2014). However, studies examining the influence of race on specific cancer-associated VTE have been scarce. To address racial disparities in cancer-associated VTE, we conducted a retrospective study in the largest safety-net hospital in New England, Boston Medical Center, with a large cancer cohort consisting of a substantial number of Black patients. This has provided a unique opportunity to directly compare the risk of specific cancer-associated VTE between Black and White cancer patients which could lead to future mechanisms-based studies.
Methods: Summary statistics were performed and presented as mean, proportion and their respective standard deviation. Differences between blacks and whites for various variables were tested using Student's t-test, Pearson's Chi-square, and Fisher's exact test as appropriate using RStudio software (v1.0.153). Logistic regression was then used to estimate and compare odds of VTE occurrence in Lung cancer after adjusting for other confounders. Statistical significance was assessed at p <0.05.
Results: We analyzed 16,498 cases with all types of solid organ and hematologic malignancies from 2004 to present (2018) with case mix characterized by Whites (53%) and Blacks (33%) and Others (11.7%). Our review of the electronic medical record revealed that 238 (1.4%) of 16,498 cancer patients had VTE, either at presentation or within one year following the cancer diagnosis. Since some VTE cases might have been undiagnosed prior to cancer development/manifestation, we used the term cancer-associated VTE to denote co-existence of these pathologies. The proportion of VTE cases were similar among male (55.5%) and female patients (44.1%). Of 238 cases of cancer presenting with VTE, Blacks predominated with 121 cases (51.3%) compared to 65 cases of Whites (27.5%). Interestingly, selected cancers were more associated with VTE in Blacks. As shown in Table 1, a significantly higher proportion of cancer-associated VTE was observed in Black patients with lung cancer, >breast cancer, >prostate cancer, >colorectal cancer and gastric/small bowel cancer; in descending order. VTE occurrence was observed predominantly in the pulmonary artery (36.9%) and femoral/iliac vein (16.1%). Sixteen percent of patients with cancer-associated VTE experienced recurrent VTE, however, no statistical difference in race was seen (p= 0.6). Given the high number of cases of lung cancer with VTE, we examined the influence of race with adjustment for confounders. Our logistic regression model showed that Black lung cancer patients have a significantly higher odds of developing cancer-associated VTE even after adjusting for cancer stage, age, and sex (OR- 2.39, CI = 1.26-4.60, p = 0.0079). Interestingly, the proportions of VTE in cancers such as pancreatic cancer, head and neck cancer and glioblastoma, were equally observed in Black and White patients, which can be ascribed to low event rates of VTE in these cancers in this series.
Conclusions: This single-center study suggests that a higher proportion of Black cancer patients exhibited cancer-associated VTE compared to White cancer patients. Importantly, this significant difference was especially reflected in specific cancer subtypes. Race had an independent effect on cancer-associated VTE but showed no significant influence on recurrent VTE. Our current investigation motivates additional large-scale studies of cohorts with substantial representation of Blacks and ethnic minorities to further identify factors that contribute to racial disparities in the context of cancer-associated VTE, thus guiding necessary interventions to maximize outcome. Our study also lays the ground for mechanistic cause-and-effect inquiries related to intricate associations of specific cancers with VTE in a certain races.
Brophy:Novartis: Research Funding.
