Despite major progress in treating breast cancer, a troubling new study shows that the number of people diagnosed with advanced, stage IV breast cancer has been steadily climbing over the past decade. This type of cancer, also called metastatic breast cancer, is the most serious form of the disease because it has already spread to other parts of the body by the time it is found.

Researchers from the Dana-Farber Cancer Institute in Boston analyzed data from a large U.S. government cancer database called SEER, which tracks cancer cases across the country. They looked at more than 761,000 patients who were diagnosed with breast cancer between January 2010 and December 2021. Their findings were published in the journal JAMA Network Open and have sparked important conversations among doctors and patient advocates.

What the Numbers Show: A Clear Upward Trend

The study found that the rate of new stage IV breast cancer cases among women rose from 9.5 cases per 100,000 women in 2010 to 11.2 cases per 100,000 women in 2021. This represents an annual increase of about 1.2 percent each year, a change that researchers say is statistically significant and cannot be explained by chance alone.

Men also saw a sharp increase in advanced breast cancer diagnoses. The rate among men went from 0.12 cases per 100,000 in 2010 to 0.20 cases per 100,000 in 2021. That is an annual increase of 3.7 percent. While breast cancer in men is rare, this rise is considered significant by the research team.

Dr. José P. Leone, the lead author of the study, noted that earlier research had found the rate of stage IV breast cancer to be stable before 2010, even as mammography and other screening tools became more common. “In contrast, our findings demonstrate a significant increase beginning in 2010, including among screening-eligible age groups,” he and his colleagues wrote. “The underlying drivers remain uncertain and may reflect population-level changes in risk factors, screening patterns, or access to care.”

Which Groups Are Most Affected?

The increase in stage IV breast cancer was not limited to one age group or ethnicity. The researchers found that the rate went up across all age groups and across nearly all racial and ethnic backgrounds. However, some groups experienced a steeper climb than others.

• Younger women under 40 had the highest overall increase in advanced breast cancer, with an annual rise of 3.1 percent. This increase was mostly driven by hormone receptor-positive cancers.
• Women over age 74 saw the biggest increase in triple-negative breast cancer, a particularly aggressive subtype, with an annual rise of 4.3 percent.
• Asian and Pacific Islander patients had the highest annual increase in stage IV breast cancer overall, at 3.4 percent per year.

These findings are especially concerning because younger women are not routinely screened for breast cancer, and older women may face barriers to regular mammograms. The study highlights that advanced breast cancer is not just a disease of older women, but increasingly affects people of all ages.

Breaking Down the Cancer Subtypes

Breast cancer is not one single disease. It has several subtypes, each with different growth patterns and treatment options. The researchers looked at how rates of stage IV disease changed for each major subtype.

The increases were statistically significant for three subtypes:

• Triple-negative breast cancer: Annual increase of 2.7 percent
• HR-positive/HER2-negative breast cancer: Annual increase of 2.0 percent
• HR-positive/HER2-positive breast cancer: Annual increase of 1.6 percent

For HR-negative/HER2-positive breast cancer, the increase was 1.3 percent per year, but this change was not considered statistically significant, meaning it could have happened by random chance.

The Good News: Survival Is Improving

While the rising number of advanced breast cancer cases is alarming, the study also brought some encouraging news. Overall survival among patients with stage IV breast cancer improved in each successive year of the study period. This means that people diagnosed more recently are living longer than those diagnosed earlier in the decade.

The improvement was seen in most subtypes:

• HR-positive/HER2-negative: Survival improved significantly each year
• HR-positive/HER2-positive: Survival improved significantly each year
• HR-negative/HER2-positive: Survival improved significantly each year

However, the improvement in survival for triple-negative breast cancer was not statistically significant. Dr. Leone and his team said this likely reflects “ongoing therapeutic challenges in this subgroup.” Triple-negative breast cancer remains harder to treat because it lacks the hormone receptors and HER2 proteins that many targeted therapies are designed to attack.

The researchers believe the overall survival improvements are largely due to advances in systemic therapy, including better chemotherapy drugs, targeted therapies, and immunotherapy treatments that have become available over the past decade.

Why Is This Happening? Experts Weigh In

The study did not identify a single cause for the rising rate of advanced breast cancer. However, the researchers offered several possible explanations. These include changes in risk factors across the population, such as rising obesity rates, delayed childbearing, and fewer women breastfeeding. Changes in screening patterns may also play a role. For example, if fewer women are getting regular mammograms, cancers may be found later, at a more advanced stage.

Access to care is another important factor. People without health insurance or with limited access to regular medical checkups may not get screened as often, and they may delay seeking care when they notice symptoms. This can lead to a diagnosis at a later, more dangerous stage.

Dr. Laura C. Pinheiro, an expert from Weill Cornell Medicine in New York City, wrote a commentary that accompanied the study. She agreed that identifying the risk factors behind the rising numbers is crucial. But she also emphasized the need to support the growing number of patients who are already living with advanced breast cancer.

“Given the tremendous physical, psychosocial, and financial burden experienced by these patients, we should prioritize supporting adults with advanced cancer throughout the cancer care continuum,” Dr. Pinheiro wrote.

What This Means for You: Practical Takeaways

This study serves as an important reminder for everyone, whether you have a personal history of breast cancer or not. Here are some practical steps you can take based on these findings:

• Know your risk factors. While some risk factors like age and family history cannot be changed, others can be managed. Maintaining a healthy weight, staying physically active, limiting alcohol intake, and breastfeeding if possible may help lower your risk.
• Stay on top of screening. Mammograms remain the best tool for finding breast cancer early, when it is most treatable. Talk to your doctor about when to start screening and how often to get mammograms based on your personal risk.
• Pay attention to your body. Know the signs of breast cancer, including lumps, skin changes, nipple discharge, or swelling in the breast or armpit. If you notice anything unusual, do not wait. See a doctor right away.
• Do not ignore symptoms because you are young. Breast cancer can happen at any age. The study found the sharpest increase in advanced disease among women under 40. If you are under 40 and notice changes in your breasts, take them seriously.
• Advocate for yourself. If you feel something is wrong, push for answers. Ask your doctor about genetic testing if you have a strong family history of breast or ovarian cancer. Knowing your genetic risk can help you and your doctor make a plan for early detection and prevention.

The Bigger Picture

The study had some limitations that are important to keep in mind. The SEER database does not include information about whether patients had mammograms, what their lifestyle habits were, or details about their socioeconomic status. This means the researchers could not directly link the rise in advanced breast cancer to specific causes like obesity or lack of screening.

Still, the findings are a clear signal that more research is needed. As Dr. Leone and his team wrote, “These findings suggest that efforts are needed to determine factors contributing to these increases and to identify breast cancer before patients present with de novo stage IV disease.”

For patients already living with metastatic breast cancer, the improvements in survival offer hope. But the rising number of new cases is a wake-up call for the medical community and the public alike. Early detection, better access to care, and continued investment in new treatments will be essential to reversing this trend.

Source: MedPage Today