8 Things You May Not Know About Breast Cancer

Breast cancer and breast cancer treatment are ever-evolving topics, especially now that it is most common and second deadliest cancer, after lung cancer, affecting women in the United States.

In 2024, one out of every eight women in the United States will develop breast cancer and approximately 42,250 women will die from it, according to American Cancer Society projections in its annual “Cancer Facts & Figures” report for 2024.

October has been designated Breast Cancer Awareness Month since 1985. We are kicking off the month with a quick rundown of eight facts about breast cancer.

Incidence is up, mortality is down

Incidence of invasive breast cancer has been creeping up by 0.6% per year since the mid-2000s, according to the American Cancer Society’s “Facts & Figures 2024” report. Excess weight — obesity increases breast cancer risk — and reproductive patterns — women having children later in life and fewer of them — are possible causes, according to the report. Meanwhile, the mortality rate has been declining from the peak year in 1989. Reasons for the decline include improved early detection and treatment. The American Cancer Society has calculated that 500,000 fewer deaths from breast cancer have occurred because the mortality rate declined from the 1989 peak.

The rising incidence is especially high among Asian and Pacific Islander Women

Between 2015 and 2019, the incidence of breast cancer among Asian and Pacific Islander women rose 2.1% annually, according to the American Association for Cancer Research’s (AACR) annual cancer disparities report. That increase was the highest for any racial and ethnic group during that period; for non-Hispanic White women, for example, the annual incidence increase was 0.5%.

Incidence, treatment of triple-negative breast cancer is not equal

Triple-negative breast cancer is an aggressive type of invasive breast cancer that disproportionately affects Black women. (It is called triple negative because the cancer cells lack estrogen, progesterone and human epidermal growth factor 2 receptors). Black women are about twice as likely to be diagnosed with triple-negative breast cancer as any other racial or ethnic group, according to the American Cancer Society. According to the AACR’s cancer disparities report, the disparity extends to treatment: Black patients with triple-negative breast cancer are 18% less likely to receive guideline-adherent treatment (including surgery, radiation, and/or chemotherapy) compared with White patients.

Breast cancer screening should start at age 40 for all women

The U.S. Preventive Services Task Force had previously recommended that women in their 40s make an individual decision, in consultation with a clinician, about whether to start breast screening. This year, the task force tightened up their recommendations to say that all women should get screened every other year starting when they turn 40, through 74. The task force also “urgently called” for more research disparities across screening and treatment experienced by Black, Hispanic, Latina, Asian, Pacific Islander, Native American and Alaska Native women.

3D mammography is racking up positive results

The technology for breast cancer screening has improved, but there are multiple juries still out about which technology should be used for which women and the tradeoffs of increased detection and false positives. Digital breast tomosynthesis (DBT), often referred to as 3D mammography, has been shown to increase the detection of breast cancer compared with traditional two-dimensional digital mammography (DM). Results of a retrospective study published in Radiology this month showed that it was also associated with fewer callbacks for more screening. These findings come after other positive findings, and the lead author heralded the results as a game changer. But researchers are still conducting studies of DBT to figure out how, and for whom, it should be used.

Women must be told about breast density

All mammography facilities in the United States are now required to notify women about their breast density. Dense breasts — which means breasts that have a greater proportion of fibrous, connective tissue and glandular tissue in contrast to fatty tissue — are associated with a higher risk of breast cancer. Dense breasts also make it harder to detect early breast cancer with mammography. The FDA rule went into effect on Sept. 10, 2024.

This antibody-drug conjugate looks promising

Antibody-drug conjugates (ADCs) that use monoclonal antibodies to hone in on cancer cells and then deliver “payloads” of cancer-killing agents to those cells are coming on strong in oncology, and breast cancer is no exception. Results presented at the American Society of Clinical Oncology earlier this year at the annual meeting in Chicago showed better results on a variety of endpoints — overall response, compete response, progression-free survival — for an ADC, Enhertu (trastuzumab deruxtecan), than for chemotherapy among patients with patients with HR-positive, HER2-low and HER2-ultralow metastatic breast cancers after they had been treated with one or more lines of endocrine therapy. The patients treated with Enhertu did, though, have a higher treatment discontinuation rate associated with adverse events compared with patients treated with chemotherapy (14.3% vs. 9.4%).

Metastatic breast cancer diagnosis ticks up after COVID-19 dip in screening, diagnosis

Cancer incidence rates fell substantially in 2020 during the first year of the COVID-19 pandemic. Cancer experts chalked it up to the massive disruption of cancer screening, including screening of breast cancer and diagnosis. As a result, many of those experts believed that there would be a spate of cancer diagnoses and of diagnoses being made at a later stage. Results reported by National Cancer Institute researchers in the Journal of the National Cancer Institute (JNCI) showed no such spurt occurred in 2021 for many cancers. Metastatic breast cancer was, however, a notable exception, with a significantly higher observed rate than the expected (a rate ratio of 1.09).

“The increased incidence of distant-stage breast cancer in 2021 compared with the expected rates indicates that the suspension of breast cancer screening during the pandemic and a potential rebound effect may have contributed to the higher observe rate of distance breast cancer in 2021,” lead author Nadia Howlader, Ph.D., and her colleagues said in the JNCI article.