Incidence of Breast Cancer According to Joint Hormone Receptor and HER2 Status Differs According to Race/Ethnicity and Other Factors
In 2010, Surveillance, Epidemiology, and End Results (SEER) registries began collecting data on HER2 receptor status in breast cancer cases. In a study reported in the Journal of the National Cancer Institute, Howlader et al identified U.S. incidence rates for breast cancer by joint hormone receptor (estrogen and progesterone receptor) status and HER2 status using SEER data. They found differences in the incidence of these subtypes by race/ethnicity, age, and other tumor factors.
Study Details
In the study, age-specific incidence rates by breast cancer subtype across the 28% of the U.S. population that is covered by SEER registries were calculated for white, black, Asian/Pacific Islander, and Hispanic women. Among 57,483 case patients, 50,571 (88.0%) had known hormone receptor/HER2 status. Of these, 36,810 (72.7%) were hormone receptor–positive/HER2-negative, 6,193 (12.2%) were triple-negative (hormone receptor–negative/HER2-negative), 5,240 (10.3%) were hormone receptor–positive/HER2-positive, and 2,328 (4.6%) were hormone receptor–negative/HER2-positive. Cases with missing hormone receptor/HER2 status tended to be black, Hispanic, older, and diagnosed with more advanced-stage disease.
Incidence Rates
White women had the highest incidence rate of the hormone receptor–positive/HER2-negative subtype (75.5%), followed by Asian/Pacific Islander (71.1%), Hispanic (68.2%), and black women (60.2%). Black women had the highest rate of triple-negative disease (22.5%), followed by Hispanic (14.7%), white (10.7%), and Asian/Pacific Islander women (9.7%). Asian/Pacific Islander women had the highest rate of hormone receptor–positive/HER2-positive disease (12.3%), followed by black and Hispanic (both 11.4%) and white women (9.8%). Asian/Pacific Islander women had the highest rate of hormone receptor–negative/HER2-positive disease (6.9%), followed by black (6.0%), Hispanic (5.7%), and white women (4.0%).
Increased Risk of Subtype by Ethnicity
On analysis controlling for race/ethnicity, age, tumor grade, and SEER registry, compared with women with the hormone receptor–positive/HER2-negative subtype: triple-negative patients were more likely to be black (odds ratio [OR] = 2.0, 95% confidence interval [CI] = 1.8–2.2) and Hispanic (OR = 1.3, 95% CI = 1.2–1.5); hormone receptor–positive/HER2-positive patients were more likely to be Asian/Pacific Islander (OR = 1.2, 95% CI = 1.1-1.4); and hormone receptor–negative/HER2-positive patients were more likely to be Asian/Pacific Islander (OR = 1.8, 95% CI = 1.5–2.1), black (OR = 1.4, 95% CI = 1.2–1.6), and Hispanic (OR = 1.4, 95% CI = 1.2–1.6).
Increased Risk by Other Factors
Patients with triple-negative (ORs = 0.9 and 0.8 for 65–74 years and ≥ 75 years), hormone receptor–positive/HER2-positive (ORs = 0.8 and 0.7), and hormone receptor–negative/HER2-positive disease (ORs = 0.7 and 0.7) were 10% to 30% less likely to be diagnosed at age 65 to 74 years or ≥ 75 years compared with hormone receptor–positive/HER2-negative patients.
Triple-negative cancers had a similar stage distribution as hormone receptor–positive/HER2-negative cancers, but hormone receptor–positive/HER2-positive cancers (ORs = 1.2 and 1.4 for stages III and IV) and hormone receptor–negative/HER2-positive tumors (ORs = 1.6 and 2.1) were more likely to present at stage III or IV. Triple-negative (OR = 20.0), hormone receptor–positive/HER2-positive (OR = 6.4), and hormone receptor–negative/HER2-positive tumors (OR = 16.8) were markedly more likely to be high grade compared with hormone receptor–positive/HER2-negative tumors.
The authors concluded:
There were marked differences in the incidence of these subtypes by age and race/ethnicity. These findings have both clinical and public health implications given differences in available treatments and risks of recurrence and mortality by subtype. For example, [estrogen receptor–negative] breast cancers are twice as likely to be missed by mammographic screening compared with [estrogen receptor–positive breast cancers]… [and] triple-negative, [estrogen receptor–positive/HER2-positive], and [estrogen receptor–negative/HER2-positive] breast cancers carry a higher risk of mortality compared with [estrogen receptor–positive/HER2-negative] tumors. Understanding of the biological basis for differences in breast cancer subtype incidence and mortality rates across population groups is limited and warrants continued intensive study. SEER data can serve in the future to monitor clinical outcomes in women with different molecular subtypes of breast cancer.
Nadia Howlader, MS, of the National Cancer Institute, is the corresponding author for the Journal of the National Cancer Institute article.
The study was supported by National Cancer Institute contracts with SEER registries.
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