A large-scale study has revealed significant racial disparities in the effectiveness of the standard CA-125 blood test for ovarian cancer detection, potentially leading to delayed treatment and poorer outcomes for Black and Native American women.
The research, published in JAMA Network Open, analyzed data from over 250,000 ovarian cancer patients diagnosed between 2004 and 2020 in the U.S. National Cancer Database. The findings show that Black and Native American patients were 23% less likely to have elevated CA-125 levels at diagnosis compared to white patients, even after adjusting for disease stage and other factors.
Racial Differences in Biomarker Levels
CA-125, a protein produced by ovarian cancer cells, has been the FDA-approved standard biomarker for ovarian cancer diagnosis and surveillance since 1981. Current guidelines consider a level of 35 U/mL or greater to be elevated, warranting referral to a gynecologic oncologist.
However, the original studies establishing this threshold were conducted in Boston and Minnesota with predominantly white populations (80% in Boston; 98% in Minnesota). The new research reveals that healthy Black women typically have CA-125 levels 10% to 37% lower than white women, while Native American women have levels up to 20% lower.
"We may be further contributing to disparities in referral, disparities in treatment, and ultimately we may be contributing to the lower survival in Black women with ovarian cancer," said lead author Dr. Anna Jo Smith, assistant professor of gynecologic oncology at the University of Pennsylvania.
Impact on Treatment Timing
The study found that patients with non-elevated CA-125 levels began chemotherapy an average of 9.38 days later than those with elevated levels. This delay was even more pronounced among Black patients, who experienced:
- A 3.14-day delay with elevated CA-125 levels
- A 4.99-day delay with non-elevated CA-125 levels
These findings are particularly concerning given that Black patients were more likely to be diagnosed at advanced stages than white patients (66.0% vs. 63.1%), yet less likely to have elevated CA-125 levels that would trigger prompt treatment.
Testing Disparities
The research also uncovered disparities in who receives CA-125 testing at diagnosis. While 84.7% of all patients had CA-125 levels measured, non-white patients were less likely to receive this testing. Lower testing rates were also observed among:
- Younger patients
- Those with Medicaid or Medicare
- Uninsured patients
- Patients with lower education levels
- Those treated at academic centers
Toward More Inclusive Standards
Dr. Shannon Westin of MD Anderson Cancer Center, who was not involved in the study, emphasized that this research illustrates the importance of studying how medical tests perform across different racial and ethnic groups.
"This is a perfect example of work that absolutely needed to be stratified based on race and ethnicity," Westin noted, adding that the findings alert doctors that they shouldn't be completely reassured by a normal test result.
Dr. Smith and her team have recently presented new research at a cancer conference suggesting a lower threshold for the CA-125 test to better detect ovarian cancer across all populations.
"New thresholds for referral will ensure that all patients get in for rapid care when ovarian cancer is suspected," Smith said.
Future Directions
The researchers acknowledged some limitations of their study, including that the database excluded patients from Puerto Rico, those treated by the Veterans Health Administration, and those cared for in small, non-National Cancer Institute-designated cancer centers.
Despite these limitations, they emphasized the urgent need for action: "Further work is needed to develop inclusive CA-125 thresholds and guidelines for an ovarian cancer diagnosis and prevent compounding disparities."
This research highlights the broader issue of medical tests and guidelines developed using non-diverse study populations, potentially contributing to health disparities that affect patient outcomes across various diseases and conditions.
