Racial Differences in the Risk of Second Breast Tumors Reported in Women With Ductal Carcinoma in Situ
Regardless of age at diagnosis, type of treatment, tumor grade or size, and tumor histology, black and Hispanic women had a higher risk of second ipsilateral breast tumors than did white women after ductal carcinoma in situ, according to the results of a large registry study presented by Liu et al in Breast Cancer Research and Treatment. In addition, there was a significantly increased risk of second contralateral breast tumors in black and Asian women, compared with white women, after ductal carcinoma in situ. To better understand the contributions of the quality of health care received and surveillance mammography to such racial disparities in the outcomes of women with this type of breast cancer, the investigators assessed the need for detailed treatment and follow-up information.
It is reported that between 10% and 24% of women with ductal carcinoma in situ experience second breast tumors 10 or more years after treatment. Of these patients, white women with invasive breast cancer seem to be less likely than their black counterparts to present with more aggressive pathology and to have lower breast cancer–specific mortality.
Study Details
The investigators conducted a comprehensive examination of the impact of race/ethnicity on second breast tumors among women diagnosed with ductal carcinoma in situ. They identified 102,489 women diagnosed with primary unilateral ductal carcinoma in situ from 18 National Cancer Institute–Surveillance, Epidemiology, and End Results registries. Of these patients, nearly 75% were white, 10% were black, 9% were Asian/Pacific Islander, and 8% were Hispanic. The mean age of these women was 58.5 years (range, 20–84 years).
A total of 27,680 women treated with mastectomy for their first ductal carcinoma in situ were excluded from the study, as they generally tend to have a low risk of ipsilateral breast tumors. Thus, 74,809 women were included in the final analysis.
The definition of second primary breast tumor included both invasive breast cancer and ductal carcinoma in situ (diagnosed at least 6 months after the first ductal carcinoma in situ). Local recurrence of ductal carcinoma in situ or invasive carcinoma in the ipsilateral breast was considered an ipsilateral breast tumor. Ductal carcinoma in situ or invasive carcinoma in the contralateral breast was considered a contralateral breast tumor.
Minorities at Higher Risk of Second Breast Tumors
The investigators found some differences in the cumulative incidence of both ipsilateral and contralateral breast tumors by race/ethnicity. During a median follow-up of 66 months, 3.9% (2,925 of 74,809 women) of women treated with breast-conserving surgery or with no surgical treatment had ipsilateral breast tumors. The 5-year cumulative incidence rate of ipsilateral breast tumors was 3.3% in black women, 3.1% in Hispanic women, 2.8% in Asian/Pacific Islander women, and 2.5% in white women (P < .0001).
According to the multivariable-adjusted analysis, black and Hispanic women had a significantly higher risk of ipsilateral breast tumors than did white women. Black women had a relative risk of 1.46 (95% confidence interval [CI] = 1.29–1.65), and Hispanic women had a relative risk of 1.18 (95% CI = 1.03–1.36).
The significant 46% increased risk of ipsilateral breast tumors in black women compared with white women was consistent regardless of age at diagnosis, receipt of radiotherapy, tumor grade, size, and architectural patterns. As for Hispanic women, there was no statistically significant difference in the risk of ipsilateral breast tumors according to tumor characteristics and treatment.
During a median follow-up of 70 months, 3.6% (3,723 of 102,489 women) developed contralateral breast tumors. According to the multivariable-adjusted risk of contralateral breast tumors, black and Asian/Pacific Islander patients (especially Filipinos) had a significantly higher risk than did their white counterparts. The relative risks were 1.21 among black women (95% CI = 1.08–1.36) and 1.16 (95% CI = 1.02–1.31) among Asian/Pacific Islander women.
The type of contralateral breast tumor played a part in the findings. For instance, the elevated risk among black patients was stronger for invasive contralateral tumors than for contralateral ductal carcinoma in situ. In contrast, the association was stronger for contralateral ductal carcinoma in situ but not for invasive contralateral breast tumors in Asian/Pacific Islander patients.
Molecular Markers Needed
“Invasive breast cancer is pathologically and biologically more aggressive in black compared to white women, largely contributing to worse prognosis for blacks,” stated the investigators. “However, the impact of black race on pathologic features and clinical outcomes of ductal carcinoma in situ remains unclear, and future research should focus on identifying molecular markers of ductal carcinoma that may explain outcome disparities.”
Ying Liu, MD, PhD, of the Division of Public Health Sciences, Washington University School of Medicine, St. Louis, is the corresponding author of this article in Breast Cancer Research and Treatment.
This study was supported by grants from the Barnes–Jewish Hospital Foundation, the Breast Cancer Research Foundation, Siteman Cancer Center, the National Institutes of Health, the National Cancer Institute, and Washington University School of Medicine Faculty Diversity Scholars Program. The authors reported no potential conflicts of interest.
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