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  • Making Sense of Breast Cancer Statistics

    Headlines & Helpful Information, Research

     

    Last month the American Cancer Society released the annual update to its “Cancer Facts and Figures,” which is one of the main sources for cancer data.  News of its release mostly centered on the fact that cancer incidence and mortality rates in the U.S. in general are declining thanks in part to steady declines in smoking, as well as advances in treatment and early detection. 

    This is all great news.  Yet some casual observers of the report noticed something that may seem confusing.  Early detection and effective treatment have improved the mortality rate for breast cancer by 40 percent between 1989 and 2016 (the most recent year for which data is available due to the significant lag required to collect and analyze it properly), yet the estimated number of breast cancer deaths (based on national mortality data between 2002-2016) has increased to more than 42,000 in 2019.  How can that be?

    The simple answer is that while the mortality rate and the actual number of deaths are both important numbers, they are used to answer two different questions.  The number of deaths show us how far we still have to go to discover and deliver the cures, while the mortality rate tells us whether we are making progress and which populations are not benefiting as much from that progress, requiring focused efforts.

    We expect the number of cases of breast cancer to increase over time because the population in the U.S. is growing.  The more people there are, the more cancers there will be.  Our population is also living longer.  Since your risk of breast cancer increases as you get older, we expect to have more breast cancers over time.  Without significant breakthroughs in treatment or improvements in access to quality care, we could expect the actual number of deaths to remain consistent or grow with the growth in population and overall incidence. 

    That’s why Susan G. Komen is focused on the estimated number of deaths per year in the U.S., which increased from approximately 41,000 to more than 42,000 since last year’s report.  Focusing on the actual number forces us to look past the good news of the decline in death rates to the underlying challenges of metastatic breast cancer and the racial/ethnic disparities that still exist. 

    That’s why in 2016 we announced a Bold Goal to cut that number in half by 2026.  We can reduce the current number of deaths by focusing on research breakthroughs that will lead to better treatments for aggressive and metastatic breast cancer; detecting recurrence earlier; and working to overcome the many barriers that prevent women from getting the care they need.  And while it may take some time to take effect and to show up in the data, which are always several years behind current activities, we have begun to lay the foundation for this progress – investing 70 percent of our 2018 research funding in grants that address metastatic breast cancer and treatment resistance, and launching a focused effort to improve death rates among African-American women in the communities where the disparity between the rates of African-American women and their white neighbors is the greatest.

    But how do we know where to target those efforts?  That’s where death rates are informative.  Death rates are adjusted for both age and size of the population and can, therefore, be used to compare deaths over time and among different populations.  For example, it is estimated that this year in Washington, D.C. there will be 100 breast cancer deaths, while in California there will be 4,560 deaths.  Just looking at the raw numbers, California has the higher number of breast cancer deaths.  Yet the raw numbers don’t take into account the number of people who live there or the age and race/ethnicity of the women in the different areas. 

    To better understand the burden of breast cancer in each area we look at the number of deaths per 100,000 people, called the death rate (or mortality rate).  When we do this, the ACS report shows there were 28.3 deaths per 100,000 people in Washington, D.C. compared to just 19.8 deaths per 100,000 in California.  By looking at the death rates we can see women who live in Washington, D.C. have higher mortality (and thus, lower survival) than women in California.  That said, there are certainly specific communities and racial/ethnic populations in California that have higher death rates than the statewide number, and which therefore require special attention.

    Overall breast cancer death rates increased slowly by 0.4 percent per year from 1975 to 1989, but since have decreased rapidly, by almost 2 percent per year for a total decline of 40 percent through 2016.  This decline in mortality is due to improved breast cancer treatment and early detection (after mammography was shown to be an effective screening tool in the late 1980s, the self-reported use of mammography in the U.S. quickly increased from 29 percent of women 40 years and older in 1987 to 70 percent by 2000).

    While we should be excited about the improvement in death rates, the numbers also show that not all women have benefited equally.  There is a striking difference in mortality trends between African-American and white women beginning in the early 1980s.  Currently, African-American women are, on average, about 40 percent more likely to die from breast cancer than their white counterparts.  This disparity is due to a combination of factors, including the timing and quality of care received and the fact that African-American women are more likely to be diagnosed younger, with a more aggressive form of the disease.  It is also influenced by other health factors, such as obesity, as well as the ability to complete treatment, as prescribed.    

    We know no single organization can do this – it takes everyone, working together. But we are committed to building on our role as leaders, conveners and collaborators to save lives.  To do less is unacceptable.

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