MBCN Responds: Metastatic Recurrence Rate Statistics

Editor’s note: Blogger Ann Silberman has asked that we link to the blog in question. We have added her name and said link.

Recently,  metastatic breast cancer blogger Ann Silberman questioned some frequently cited statistics concerning the number of people treated for early stage breast cancer who go on to have a metastatic recurrence. The blogger suggested that the Metastatic Breast Cancer Network (MBCN) was the source for a Facebook graphic which decries the number of early stage breast cancer patients who go on to have a metastatic recurrence. MBCN is not the source for this artwork–the graphic’s creator has indicated she corresponded with another breast cancer organization to arrive at the stated number.

MBCN also would like to note the discrepancy between the blogger’s account of the given statistic and what the MBCN site actually says. Please note that the statement on our website is carefully worded. It says: “It is estimated that 20 to 30% of all breast cancer cases will become metastatic.”  Here is a screenshot of the MBCN webpage:

Why Does MBCN Have This Statement on its Website?

The numbers were cited by an oncologist who treats and does research on behalf of metastatic breast cancer patients. More significantly, it highlights a critically important issue: Despite excellent standard of care for people with early stage patients, some patients go on to receive a metastatic diagnosis 5, 10, 15 and even  20 years later. Scientists do not know why this happens–and unfortunately, there is no cure for metastatic breast cancer.

Why Is the Recurrence Rate So Important?

We need the public and early stage patients to support metastatic research because no one can be told with absolute confidence that they are cured after treatment for early stage breast cancer. Note this 2011 presentation:

Source: Musa Mayer, http://advancedbc.org/files/Mayer_NBCC_2011_0.pdf

Why Is is it So Difficult to Find MBC Reccurence Rates?

Oncologists and researchers often refer to the heterogeneity of breast cancer, meaning it isn’t one disease. Triple-negative subtype, for example generally have a higher metastatic recurrence risk vs. the hormone-positive disease. Tumor size and node involvement also can play a role in an individual’s risk for recurrence. The more conservative 20-30% figure MBCN uses is an aggregate number that includes Stages I-III, with much lower percentages for Stage I.

Another reason for the scarcity of statistics is that patients with recurrences are not counted.

• NCI and SEER databases record  incidence, initial treatment and mortality data. Most people do NOT present with metastatic diagnosis. The cancer registry does not track recurrence—which is how the majority of people are thrust into the metastatic breast cancer ranks.
• We estimate that there are 150,000 US people currently living with metastatic breast cancer, but we don’t know exact numbers.
• We know for sure that almost 40,000 US people die from breast cancer every year. We know that 5 to10 percent of those with metastatic breast cancer were Stage IV from their first diagnosis. So what about the 90 to 95% of those 150,000 currently living with metastatic breast cancer  who were previously treated for early stage breast cancer? The cancer registry does not track them—until they die. (Here is a general explanation of how cancer registries work. And here is an overview of some epidemiology basics.)

What Is MBCN Doing to Ensure People with MBC are Counted?

MBCN is a founding member of the Metastatic Breast Cancer Alliance which is currently collaborating with other agencies and registries to initiate a epidemiology pilot study designed to achieve more accurate data about the prevalance and disease course of MBC. On August 11, 2015, the Alliance will offer a free webinar to provide an update on its activities.

Is This Statistic Too High or Too Low?

We don’t know– and frankly no one does. As noted above,  there are currently massive gaps in how people with metastatic breast cancer are counted.  But there are certainly some who feel strongly the number is lower rather than higher.  The following is from ACS Breast Cancer Facts and Figures 2013-14

Breast Cancer Survival and Stage at Diagnosis

 Relative survival rates are an estimate of the number of patients who will survive for a given time after a cancer diagnosis.  It differs from observed survival in that it accounts for deaths from other causes by comparing among cancer patient to survival among people of the same age and race who have not been diagnosed with cancer.  

 Based on the most recent data, relative survival rates for women diagnosed with breast cancer are:

•  89% at 5 years after diagnosis
• 83% after 10 years
• 78% after 15 years

“Of course, women keep dying of MBC longer than 15 years after their initial diagnoses,” notes Musa Mayer, patient advocate and Member, Steering (Executive) Committee, Metastatic Breast Cancer Alliance. “According to SEER statistics:  18 year relative survival for patients diagnosed from 1990-1994 is 71% which takes us really close to the 30% figure.  However, it’s important to bear in mind that none of these patients would have been offered Herceptin, not even in the metastatic setting.  With adjuvant Herceptin cutting recurrence rates in half, this is a big difference.  Fewer hormonal options existed as well.”

Unfortunately, Herceptin is not an option for all breast cancer patients. HER2 positive breast cancer--i.e., the subtype Herceptin targets–accounts for about 15 to 20 percent of all breast cancers;  ER/PR+; HER2-  is the most common subtype, accounting for 65% of breast cancer cases;  the triple negative subtype accounts for 15% of breast cancer cases.

What About Mortality Rates?

Some argue that mortality numbers tell the story more precisely than survival numbers. Screening skews the survival numbers:  The more we screen, the more we diagnose and treat women with breast cancers that would not have been a threat to their lives,  so it looks like relative survival for early stage breast cancer is 89 percent.  Yet an estimated 40,000 US people die annually from metastatic breast cancer.

Earlier this year, Dr. Aaron E. Carroll wrote a New York Times article called “Why Survival Rate Is Not the Best Way to Judge Cancer Spending.” His explanation of over diagnosis bias is compelling:

Let’s say that a certain number of cases of [mythical]  thumb cancer that are detectable by scan never progress to a lump. That means some subclinical cases that would never lead to death are now being counted as diagnoses.

Since they were never dangerous, and we’re now picking them up by scans, they’re improving our survival rates. But they do nothing for mortality rates because no fewer people are dying. . . For many cancers, we’ve been diagnosing significantly more cases, but making little headway in mortality rates.

What’s Next?

MBCN prides itself on being a credible source of information for the metastatic breast cancer community. Unfortunately even the most well-meaning individual can misinterpret and/or  misattribute statistics. We do our best to present accurate information–we ask others to do likewise.

We understand the keen interest in recurrence statistics. We are doing a literature search and will report those findings shortly–but we expect those findings will closely track with all that we have said here.

We are working to change how metastatic breast cancer recurrences are tracked. But in 2015 this information remains undocumented. On the positive side, there have been some advances in the adjuvant treatment of early breast cancer over the past decade. This includes the use of adjuvant Herceptin, the use of adjuvant taxanes with AC regimens in triple-negative breast cancers and some incremental improvements in  hormonal treatment. And yet we still lose 110 US people to metastatic breast cancer every day. Clearly much work remains to be done.

Finally, we urge people not to apply  population-based statistics to their individual cases–we are each statistics of one!