When compared with the general population, patients with cancer-associated thrombosis (CAT) have substantially higher risk for developing venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE). “Between 500,000 and 1,000,000 new VTE cases occur each year in the United States,” says Ted Wun, MD, FACP. “CAT is a common and comorbid complication of cancer. Current estimates show that about 6% of all patients with cancer have CAT and about 20% of all patients with VTE have cancer.”

Racial/ethnic disparities in the incidence of VTE have been documented in the general population, but Dr. Wun says little is known about VTE incidence in patients with cancer. “CAT is preventable with thromboprophylaxis, but this treatment is likely underutilized due to perceptions of high risk for bleeding,” he says. “Identifying patient populations at higher risk for CAT would allow for targeted prophylaxis in which the benefits outweigh the risks.”

For a study published in Blood Advances, Dr. Wun and colleagues examined associations between race/ethnicity and the incidence CAT in a large, diverse population of patients with cancer. Using the California Cancer Registry linked to the California Patient Discharge Dataset and Emergency Department Utilization database, the investigators studied more than 942,000 patients with the 13 most common, first primary malignancies from 2005 to 2017. Participants had at least one hospital admission or emergency department visit prior to or after their cancer diagnosis.


Blacks/African Americans Have Higher Risks for CAT  

Among all participants, 6.6% developed a CAT, of whom 63.1% were White, 17.4% were Hispanic, 10.6% were Black/African American, 8.0% were Asian/Pacific Islander, and 0.9% were other or unknown race or ethnicity. “After adjusting for other potential risk factors, we found that Blacks/African Americans had an overall higher risk of CAT, whereas Asian/Pacific Islanders had a lower risk,” says Dr. Wun. “These differences were primarily driven by the incidence of PE, which represents the more serious form of CAT.”

Blacks/African Americans had a higher incidence of CAT for all tumor types except myeloma (Figure). Blacks/African Americans also had the highest cumulative incidence of PE plus DVT events for all cancer types except bladder cancer and myeloma. Conversely, Asians/Pacific Islanders had the lowest 12-month cumulative incidence of CAT for all cancer types and a statistically lower incidence than others in seven of the 13 cancer sites. In addition, Asians/Pacific Islanders had the lowest cumulative incidence for PE plus DVT events among all cancer types.


Data Can Inform Decisions on Primary Prophylaxis for CAT

The findings suggest that race and ethnicity should be considered, along with other predictive tools, when making decisions on primary prophylaxis for CAT. However, this is counter to the current trend of eliminating race-based adjustments in medicine and the downstream consequences that may further exacerbate health inequities and disparities.

“When patients present with signs or symptoms consistent with CAT, clinicians might have a lower threshold for diagnostic testing if they are managing people who self-identify as Black/African American,” Dr. Wun says. “Similarly, race might be a consideration when deciding on primary prophylaxis to prevent CAT in patients with high-risk tumors. However, these statements should be taken with great caution, because race/ethnicity categories are imprecise. Associations between race/ethnicity and outcomes may not be generalizable to other societies and cultures with different healthcare systems.”


Consider Impact of Social Determinants of Health

The study team noted that the reasons underlying the observed racial/ethnic differences in CAT are still unknown. “The disparities seen in our study are unlikely to be due to genetic variations alone,” says Dr, Wun. “Further research is needed to determine how various causative factors are mediated by race/ethnicity. Although genetic differences may play a role, social determinants of health—such as access to care and quality of care—may also be factors. Disparities between racial/ethnic groups should also prompt more research into the reasons why CAT has higher incidence in some groups. This might include studies on genetic variations based on ancestry, inequitable access to care, and other social determinants of health.”