The research was published in the September 2021 issue of the journal Cancer Medicine. Triple-negative breast cancer is estrogen-receptor-negative, progesterone-receptor-negative and HER2-negative.
Triple-negative breast cancers are usually more aggressive, harder to treat, and more likely to come back (recur) than cancers that are hormone-receptor-positive or HER2-positive. Triple-negative breast cancers don’t usually respond to hormonal therapy medicines or medicines that target the HER2 protein.
Hormone-receptor-positive HER2-negative breast cancer is the most common subtype of breast cancer, accounting for about 73% of all cases. Treatments that target the hormone receptors and HER2 receptors have improved outcomes, but there are still large differences in survival between the various subtypes of breast cancer. For example, the 5-year survival rate for hormone-receptor-positive HER2-negative breast cancer is near 95%, but is only about 75% for triple-negative breast cancer.
The researchers who did this study wanted to look at the relationship between the subtype of breast cancer diagnosed and certain breast cancer risk factors.
The study included information from 198,278 women aged 40 to 84 who had a screening mammogram at two hospitals in Massachusetts or through the University of Pennsylvania Health System between 2010 and 2015.
None of the women had been diagnosed with breast cancer when they had their screening mammograms.
Of the women in the study none had a known BRCA1 or BRCA2 mutation, 11% had a previous breast biopsy, 0.9% had been previously diagnosed with atypical hyperplasia, a benign breast condition that increases the risk of breast cancer in the future, 50.4% were 12 or 13 years old when they had their first period, about 40% were between age 20 and 30 when they gave birth to their first child, and 21.3% had never given birth, 87.3% had no family history of breast cancer, 73.7% were white
15% were black, 11% were Hispanic/Latina, Asian/Pacific Islander, or another race, 38.3% had a BMI of less than 25, considered to range from underweight to healthy, 24.9% had a BMI of 25 to 29.9, considered overweight, 25% had a BMI of more than 30, considered obese, 58.2% were postmenopausal, 82.5% had a BI-RADS breast density score of B or C (B means the breasts are mostly fatty tissue, but also have scattered dense areas, and C means there are many dense areas), 7.9% had a BI-RADS breast density score of D, meaning the breasts are extremely dense and follow-up time ranged from 4.2 to 9 years.
During follow-up, 4,002 invasive breast cancers were diagnosed in the women in the study:
77.6% were hormone-receptor-positive HER2-negative
7.5% were triple-negative
8.5% were hormone-receptor-positive HER2-positive
3.2% were hormone-receptor-negative HER2-positive
The researchers didn’t have subtype information for about 4% of the breast cancers. The researchers used statistical analysis to look at links between the risk factors and the subtype of cancer diagnosed.
As the researchers expected, a diagnosis of hormone-receptor-positive HER2-negative breast cancer was associated with well-documented risk factors:
older age, having a previous breast biopsy, having a previous diagnosis of atypical hyperplasia, having a family history of breast cancer, having a BMI of 25 or greater and having a BI-RADS score of B, C, or D.
Only four risk factors were associated with a diagnosis of triple-negative breast cancer: older age, being black
having a BMI of 25 or greater and having a BI-RADS score of B, C, or D.
The analysis showed that black women were 2.7 times more likely to be diagnosed with triple-negative breast cancer than white women. Women with extremely dense breasts — a BI-RADS score of D — were 3.4 times more likely to be diagnosed with triple-negative breast cancer than women with a BI-RADS score of A, which means the breasts are mostly fatty and not dense.
Dense breasts were more strongly associated with a diagnosis of hormone-receptor-positive HER2-negative in premenopausal women than in postmenopausal women.
Dense breasts were more strongly associated with a diagnosis of triple-negative breast cancer in premenopausal women than in postmenopausal women; premenopausal women with dense breasts were 2.8 times more likely to be diagnosed with triple-negative breast cancer than premenopausal women with non-dense breasts.
The researchers found that women who had more children had a lower risk of being diagnosed with hormone-receptor-positive HER2-negative breast cancer than women who had fewer children.
Finally, the researchers looked at how frequently certain breast cancer subtypes were found during routine mammograms versus those categorized as interval breast cancers. The National Cancer Institute defines interval breast cancer as a breast cancer that is found between a screening mammogram with normal results and the next screening mammogram. Interval breast cancers tend to be larger and grow and spread more quickly than breast cancers found by a routine mammogram.
Triple-negative breast cancers were 33% less likely to be found during a routine mammogram and more than 2 times more likely to be interval cancers than hormone-receptor-positive HER2-negative breast cancers. – Source: www.breastcancer.org