Breast Cancer Risks Climb in Some Populations

Over the past 15 years, Asian Americans have experienced an increase in breast cancer rates, while diagnosis rates among other racial and ethnic groups have largely been on a downward trend.

The authors of a new study published by Breast Cancer Research and Treatment examined potential contributing factors by looking at age and breast cancer stage among 7 Asian American ethnic groups located in California. Included in the study were 45,721 Asian American patients diagnosed with invasive breast cancer from 1988 to 2013.

Previous studies have looked for subtype-specific patterns among Asians/Pacific islanders as a group. This is the first to examine subtype-specific patterns among Asian American ethnicities and variation among the groups.

The authors examined patients with breast cancer from 7 major Asian American ethnicities: Chinese, Japanese, Korean, Filipino, Vietnamese, South Asians, and Southeast Asians.

The investigators discovered that, other than the Japanese group, all groups had an increased incidence of breast cancer from 1988 to 2013. The most substantial increase was observed among Koreans, South Asians, and Southeast Asians, according to the study.

The authors also found an increase in metastatic breast cancer among patients from the Philippines.

Among patients aged 50 and older, there was an increase in breast cancer incidence among all ethnic groups, while the increase among patients younger than 50 was only seen in the Vietnamese and other Southeast Asian groups, according to the study.

Despite the overall rate continuing to increase, the authors found that rates for patients under 50 of Japanese and Filipina descent were comparable to breast cancer rates among whites.

The authors also discovered that the rate of breast cancer incidence also varied among disease subtype. Among Korean, Filipino, Vietnamese, and Chinese patients, there was a higher incidence of human epidermal growth factor receptor 2 (HER2) disease, according to the study.

High rates of late-stage breast cancer among Filipino, Korean, and South Asian women suggest that these populations may require more frequent or a higher uptake of mammograms, the authors said.

The increasing rates of HER2-negative disease requires additional research, since this breast cancer subtype is more aggressive than others.

The authors note that mammography screening in Asian American patients in California is lower than other racial/ethnic groups. In particular, Korean and South Asian women have the lowest rates of mammography, which may explain why these groups have higher incidences of late-stage breast cancer, according to the study.

“These patterns warrant additional attention to public health prioritization to target disparities in access to care, as well as further research in identifying relevant breast cancer risk factors for specific breast cancer subtypes,” said lead researcher Scarlett Lin Gomez, PhD, MPH. “In particular, studies should investigate risk factors, perhaps early-life exposures, underlying the higher rates of breast cancer among young Filipino and Japanese women, with attention to possible genetic susceptibility.”