Malay race a poor prognostic factor for breast cancer control, deaths
Women of Malay ethnicity appear to have poorer prognosis for invasive ductal carcinoma (IDC) of the breast compared with women of Chinese and Indian ethnicity, with higher risks of all-cause mortality and breast cancer-related deaths, according to a Singapore study.
Researchers looked at 6,180 women with IDC, 11 percent (n=702) of whom were Malay. [J Breast Cancer 2017;20:183-191]
Malay women had the highest human epidermal growth factor receptor 2 positivity rate compared with Chinese and Indian women (30.7 percent vs 23.9 percent and 20.6 percent, respectively) and the highest incidence of grade 3 tumours (61.8 percent vs 45.8 percent and 52 percent), T3 and T4 tumours (14.2 percent vs 8.7 percent and 9.6 percent), and node-positive disease (58.3 percent vs 46.4 percent and 54.9 percent).
After adjusting for age, histology subtype, and disease stage, Malays had poorer overall survival (OS; hazard ratio [HR], 1.44; p<0.001), disease-free survival (DFS; HR, 1.17; p=0.101), and cancer-specific survival (CSS; HR, 1.49; p=0.003) rates than Chinese and Indian participants, all of which remained poor at 5 and 10 years (p<0.001 for all survival rates).
“The OS, DFS, and CSS differences become even more marked at 10 years postdiagnosis, as breast cancer can be indolent and have a long natural history,” said the researchers.
Survival outcomes were worse in screen-detected vs clinically detected tumours in Malay women (HR, 5.78 vs 1.44 for OS, HR, 2.18 vs 1.10 for DFS, and HR, 5.93 vs 1.53 for CSS).
“[E]ven among screen-detected cancers, Malay breast cancer patients had poorer disease control and survival than ethnic Chinese and Indian patients. This unexpected observation belies the fact that screen-detected cancers are more indolent,” said the researchers, highlighting the need for further evaluation.
With poor prognostic factors and the increased likelihood of having biologically aggressive disease, chemotherapy and targeted therapy rates were higher in Malays (72.2 percent and 16.7 percent, respectively) than Chinese (55.8 percent and 10.5 percent) and Indians (61.5 percent and 10.9 percent).
“[Our findings suggest that] race remained independently significant for survival outcomes … Malay patients may have distinct differences in the natural history of breast cancer and may respond differently to standard breast cancer treatment,” said the researchers.
“Malay women had more advanced disease at presentation and hence, poorer outcomes as a direct result of lower breast cancer screening uptake and delays in seeking help; such behaviour may have compounded the risks conferred by inherent genetic factors,” said the researchers.
The results highlight the importance of breast cancer detection and follow-up in this ethnic group to clarify the cultural and genetic influences on breast cancer survival outcomes, they noted. “Public education, screening, treatment, and surveillance measures may be implemented with consideration of race.”