African-American women with early-stage breast cancer are more likely than their Caucasian counterparts to experience a relapse after breast-conserving therapy, but the absolute difference in risk is small
LOS ANGELES-African-American women with early-stage breast cancer are more likely than their Caucasian counterparts to experience a relapse after breast-conserving therapy, but the absolute difference in risk is small, Meena S. Moran, MD, of Yale University School of Medicine, reported at the 49th annual ASTRO meeting (abstract 8).
In the retrospective study, the investigators compared outcomes by race using data from the 207 African-American women and 2,164 Caucasian women treated with breast-conserving therapy at Yale between 1975 and 2003. All had been treated with whole-breast radiation therapy. The mean dose delivered (whole breast plus boost) was 64 Gy. Some patients also received regional nodal radiation therapy and systemic chemotherapy at the discretion of their treating physician. Expression of p53 was assessed in a blinded fashion in 19% of women. The median follow-up was 7 years.
The methods of cancer detection did not differ significantly between African-American and Caucasian women, with 45% of tumors detected by mammography alone in each group. Similarly, treatment did not differ significantly by race: Women in both groups had similar numbers of lymph nodes removed (8 on average) and were similarly likely to have positive margins (about 10%) and to receive chemotherapy and tamoxifen; the chemotherapy regimens did not differ between groups. Finally, the groups did not differ with respect to family history of breast cancer and histologic type.
However, African-American women were significantly more likely than Caucasian women to be aged 40 years or younger at diagnosis (20% vs 12%) and to have pT2 tumors (32% vs 18%). They were marginally more likely to have positive nodes (32% vs 24%). In addition, African-American women were significantly more likely to have tumors that were ER negative (54% vs 36%), PR negative (58% vs 47%), triple negative (21% vs 8%), and p53 positive (32% vs 13%).
In univariate analyses, compared with Caucasian women, African-American women had higher 10-year rates of breast relapse, nodal relapse, and distant relapse, Dr. Moran said. However, she noted, the differences were small in absolute terms (see Table). In multivariate analyses adjusted for race, age, T stage, nodal status, and margin status, African-American women still had a significantly higher risk of breast relapse (RR 1.6) and nodal relapse (RR 3.1).
"While we have shown that African-American patients have higher local recurrence rates after breast-conservation therapy, we believe that conservative surgery and radiation therapy remains a reasonable option for those African-American patients wishing to conserve their breast, provided that the clinical scenario is appropriate," Dr. Moran said.
Be aware of higher risk
She pointed out that clinicians involved in the care of African-American patients need to be aware of this higher risk and consider all factors that optimize local-regional control.
These factors include assuring negative margin status, adequately boosting the tumor bed, and assuring optimal dose delivery and radiation coverage to the breast and regional lymph nodes if clinically indicated, and adequate treatment to the axilla, either complete nodal dissection or radiation therapy, if indicated.
Dr. Moran acknowledged that related but unmeasured confounders, such as treatment compliance and dose delays and reductions, may be affecting these outcomes. The Yale researchers are currently evaluating these parameters.
"Lastly, we emphasize the need for clinicians to encourage their African- American patients to enroll in studies to improve the understanding of the ethnicity-based differences in breast cancer," she said. "We hope that future evaluation of the underlying molecular, genetic, and biological variables will lead to strategies to optimize treatment outcomes for our African-American patients."