A new study led by UC San Francisco has found an alarming rise in invasive breast cancer among Asian American women over the last two decades.
Rates are rising among nearly all Asian American ethnic groups much faster than they are in any other U.S. ethnic group; and this is especially true among women who are under 50 and have advanced stage or certain aggressive subtypes of breast cancer.
The study, published in JAMA Network Open , found that breast cancer incidence increased by more than 3% per year in nearly every Asian American ethnic group, and it rose even higher for Chinese and Vietnamese women. Breast cancer rates for Native Hawaiian women are among the highest for U.S. women, but the study found that they increased by just 1% per year, which is lower than what was seen in Asian American groups.
The researchers said the increase is probably unrelated to screening, which is most likely to increase early-stage diagnoses. Cancers that had already spread increased the most rapidly. Triple-negative breast cancer, considered the most aggressive subtype, increased more than 6% each year between 2017 and 2022 among Chinese American women.
"These patterns are highly concerning from a disparities standpoint," said senior author Scarlett Lin Gomez , PhD, professor of epidemiology and biostatistics at UCSF and co-leader of the Cancer Control Program at the UCSF Helen Diller Family Comprehensive Cancer Center . "They underscore why it is so important to move beyond treating Asian Americans, Native Hawaiians, and Pacific Islanders as a single population."
An updated look at risks for Asian Americans, Native Hawaiians, and Pacific Islanders
The researchers analyzed about 150,000 cases of invasive breast cancer diagnosed between 2000 and 2022 using data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program. The study included nine detailed Asian American, Native Hawaiian, and Pacific Islander (AANHPI) populations from 14 states that have about two-thirds of the U.S. AANHPI population.
Except for Native Hawaiian women, Asian American women have historically had lower rates of breast cancer than non-Hispanic white women, but that gap is narrowing rapidly. By 2022, the incidence for Asian American women under 50 was comparable to that of white women.
The reasons behind the increase in breast cancer in women under 50 are unclear. Changing reproductive patterns, diet, and other lifestyle factors may play a role, but the researchers said they do not entirely explain the findings.
The rises in some Asian American communities may be due in part to as yet undiscovered risk factors. The researchers hope that two UCSF-based studies, the CRANE breast cancer study and the ASPIRE cohort study, will provide insights into these factors.
"Understanding why breast cancer is increasing so rapidly in these communities is critical," Gomez said. "At the same time, we need to ensure that women across all Asian American, Native Hawaiian, and Pacific Islander communities have access to culturally appropriate education, screening, and timely follow-up care."
Authors: Other UCSF authors are Meg McKinley, MPH; Katherine Lin, MPH; Iona Cheng, PhD; and Salma Shariff-Marco, PhD.
Funding: The Breast Cancer Research Foundation, the National Cancer Institute's SEER Program, and the Surveillance Research Program Division of Cancer Control and Population Sciences of the National Cancer Institute.
About UCSF: The University of California, San Francisco (UCSF) is exclusively focused on the health sciences and is dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care. UCSF Health, which serves as UCSF's primary academic medical center, includes top-ranked specialty hospitals and other clinical programs, and has affiliations throughout the Bay Area. UCSF School of Medicine also has a regional campus in Fresno. Learn more at ucsf.edu or see our Fact Sheet .
