SAN ANTONIO – Women who have small, early stage breast cancers discovered on mammogram have excellent survival – but the rates are significantly lower among black women when compared with whites, researchers said here at the annual San Antonio Breast Cancer Symposium.
The 5-year disease specific survival was 99% in white women compared with 94% in black women (P<0.0001), said Mahvish Muzaffar, MD, of East Carolina University, Greenville, North Carolina.
Overall 5-year survival was 93.7% among white women who were diagnosed with pT1aN0 or pT1bN0 tumors – generally less than 1 cm in diameter – but for black women with the same disease the overall survival was 91.5% (P<0.0001).
“I think these findings should be very encouraging for all women who have these small, early cancers that are found with mammography,” Muzaffar told MedPage Today. “But we still don’t know why there is still a difference in outcomes by race.
“Very early breast cancer is associated with excellent outcome but has some heterogeneity,” she said at her poster presentation. “Conventional prognostic factors are not sufficient to risk stratify very early breast cancer and molecular profiling may help identify patients who will need adjuvant therapy.”
Muzaffar said that “when we looked to see if there was a subset of patients who do not do as good, race stood out. Whites and others such as Asians did better than African Americans. Out first thoughts was that difference could be explained by socioeconomic status and/or access to care, but lately we are seeing data that there may be a biological factor involved. We thought that the differences may have been that the African Americans do not get timely care and they don’t get the right care and they may not have insurance and therefore they get sub-optimal care.”
But Muzaffar said, “Other studies have accounted for those differences in care, and yet African-American women in those studies still had worse outcomes. These factors may explain a large chunk of the difference – but they don’t explain everything.
“While all these results are still very good, there are still differences,” she said. “In this day and age, we should have equity.
“It is possible that the African-American population may have breast cancer that it slightly more aggressive disease than that seen among non-black patients,” Muzaffar said. “What we probably need is to do African American-centric studies to try to figure out what is driving this difference.”
The disparities by race also caught the attention of Jennifer Litton, MD, of the University of Texas MD Anderson Cancer Center in Houston. “Even when we look at outcomes on clinical trials where everything is the same as far as access to care is concerned, we still often see discrepancies between outcome of blacks and whites. I think this just highlights the need for looking for underlying factors,” she said.
“Hopefully if we continue to look at patients’ tumors we may be able to find some biological difference. There are definitely discrepancies in pharmacodynamics. It means we really need to continue to investigate because it is important to figure this out,” she told MedPage Today.
To perform the trial, Muzaffar and colleagues accessed the federal Surveillance, Epidemiology and End Results (SEER) database and identified 50,796 women during the years 2006 and 2011 who had small, early stage breast cancer. Mean age was 62; 85% were white and 7% were African American.
For the entire group, 5-year disease specific survival was 98.7% and overall 5-year survival was 93.7%. Disease specific survival for women with estrogen receptor positive cancer was 99% compared with 96% for women with estrogen receptor negative early stage cancer (P<0.0001); overall 5-year survival was 94% for women with estrogen receptor positive cancer and 92% for women diagnosed with estrogen receptor negative disease (P<0.0001).
About 72% of the women were diagnosed with pT1bN0 breast cancer – 36,347 individuals; 28% were pT1aN0 breast cancer or 14,449 individuals. Only 11% of the women were estrogen receptor negative.
Muzaffar and Litton disclosed no relevant relationships with industry.