SAN ANTONIO—Key to using disparities research is understanding the underlying causes, experts said about a study of sentinel lymph node biopsy (SLNB) in black patients versus white patients presented here at the CTRC-AACR San Antonio Breast Cancer Symposium. Despite increased use of SLNB, and its becoming the accepted standard of care for axillary staging of node-negative breast cancer patients, data show disparities as high as 13 percent in its use in black patients for whom the procedure was deemed appropriate compared with white patients, the researchers reported. That disparity translated to a double risk of lymphedema for black patients because they were more likely to receive axillary node dissection.
“The lag in care—not doing the recommended treatment—actually does matter for patient outcomes,” the lead author of the study, Dalliah M. Black, MD, Assistant Professor in the Department of Surgical Oncology in the Division of Surgery at The University of Texas MD Anderson Cancer Center, said in an interview after the meeting.
“The real question in my mind is, ‘Why is there this difference?’” Peter Ravdin, MD, PhD, one of three Co-Directors for the meeting, said in a phone interview afterwards. He also serves as Director of the Breast Health Clinic at the Cancer Therapy & Research Center at the University of Texas Health Science Center. The study used the Medicare population—which is interesting because all of the women were to some extent insured, thus eliminating that major economic barrier to receiving care, he noted.
Black and her colleagues studied 31,274 patients with pathologic node-negative invasive breast cancer with no evidence of metastatic disease and who had a documented axillary surgical procedure, using the National Cancer Institute's population-based Surveillance, Epidemiology, and End Results (SEER)-Medicare database. They tested whether race was associated with the use of SLNB after adjusting for clinicopathologic factors. All patients were diagnosed between 2002 and 2007 and had fee-for-service coverage.
The data showed:
- An absolute difference of 12 percent for overall use of SLNB in white patients compared with black patients—the procedure was performed in 74 percent of white patients compared with 62 percent of black patients;
- Use of SLNB increased by year for both black and white patients, but the disparity of its use in whites compared with blacks persisted through the duration of the study period (2002 to 2007); and
- For patients diagnosed in 2007 when SLNB was the preferred method for axillary staging, the procedure was used in just 70 percent of black patients compared with 83 percent of white patients.
The data also showed that patients receiving axillary node dissection had a higher risk of lymphedema at five years (12%) compared with patients receiving sentinel node biopsy (7%). This finding explains why, overall, black patients in the study had a higher risk of lymphedema compared with white patients—because they were more likely to have received axillary node dissection, Black said. But among all patients undergoing SLNB, whites and blacks had similar risks of lymphedema.
Using a multivariate analysis, the researchers determined that racial disparity in SLNB use was independent of the type of surgery performed, for either lumpectomy or mastectomy. For the study cohort, 5.7 percent of patients were black, 89 percent were white, and 5.3 percent were of other or unknown race. The patients' median age was 74.
Underlying Issues Still Not Understood
“The reasons underlying these racial differences are complex and likely multi-factorial,” Black said. Previous studies have shown similar disparities in use of SLNB in black patients versus white patients using earlier time limits, and also that patients (white and black) are more likely to receive SLNB when treated at academic centers versus community hospitals, Black said.
But, this study adds more current data though about SLNB use in blacks and looks more closely at the adverse clinical outcomes that result from the disparity in care—the increased risk of lymphedema in blacks less likely to receive the newer treatment. And, using the SEER/Medicare data gives an idea of what is going on across the country in general, not just in academic centers, Black said.
“In our study, race still was an independent predictor of SLNB use,” she said. But, preliminary data suggested that patients were less likely to receive SLNB if they were from a region of lower income, lower education, or lower surgeon density, or if they had Medicaid, Black added. The next step is to evaluate SLNB use by hospital type and adjust for characteristics of the surgeon (such as level of fellowship training, age of surgeon, sex of surgeon), to determine whether the racial disparity still existed in use of SLNB despite those other factors—and assess which underlying reasons are driving the disparity.
Closing the “Quality Chasm”
This study adds to the growing body of data showing the unequal dissemination of cancer care often referred to as the “quality chasm,” said Rena J. Pasick, DrPH, Professor of Medicine and Assistant Director for Community Education & Outreach at the Helen Diller Family Comprehensive Cancer Center at UCSF, commenting on Black's study for this article. Pasick also serves as a member of the American Association for Cancer Research Cancer Health Disparities Conference Scientific Program Committee.
“It is not that doctors in community settings are withholding better treatments from African Americans; they may not be practicing those treatments at all,” she said via email. Research shows that the people least likely to receive the latest cancer treatments are the uninsured or underinsured, and African Americans are disproportionately concentrated among the poor and underinsured, she explained. “Scientific advances have been estimated to take about 17 years to work their way out into the world of general practice.”
The pace and extent of adoption of new treatments is the major disparity of concern here, William Nelson, MD, PhD, Professor and Director of Johns Hopkins Kimmel Cancer Center, said via email. Research is needed to determine how best to improve outcomes, he said. Nelson has served as Chair of the AACR Cancer Health Disparities Conference for the last two years.
“Focused education of breast surgeons and breast pathologists could be helpful,” he noted. “I believe that progressive improvements in electronic medical record technologies will make these issues easier to monitor and easier to improve.”
During her presentation, Dr. Black noted the following as next steps:
- Collect more contemporary research: She said she plans to continue the study using the 2010 SEER/Medicare data to see whether the disparity in use of SLNB persisted after 2007. She also plans to look at SLNB use as recorded in the Texas Cancer Registry, which has higher rates of Hispanic women (for whom use of SLNB was actually lower even than in black women). “Really, both of those groups should be looked at,” she said.
- Develop more focused education: Focused education should be broadly instituted in order to implement new practice recommendations to ensure that all patients benefit from improvements in breast cancer care, Black said. Patients need to be educated to ask the right questions, and physicians need education on the latest guidelines and practices. “We need to understand some of the driving forces between the surgeons and the patients and the multidisciplinary care team,” she said.