American women with metastatic breast cancer (MBC), the only form of the disease that is deadly, are now living longer than they did in the early 1990s, according to new research.
The investigators also provide, for the first time, an estimate of the number of women living with MBC in the United States.
The team, led by Angela Mariotto, PhD, an epidemiologist at the National Cancer Institute (NCI), specifically investigated women who had been diagnosed with de novo MBC (ie, cases in which the original diagnosis was metastatic, not cases of early-stage disease progression). They found that overall survival had improved in recent years compared to the early 1990s.
For all age groups (including patients aged 85 years and older), the median relative survival improved from 16.7 months to 26.9 months from the periods 1992-1994 to 2005-2012.
"This study confirms what we have known intuitively...that women are living longer with the disease," said Richard Bleicher, MD, a breast surgeon at Fox Chase Cancer Center in Philadelphia, Pennsylvania, who was asked for comment.
This study confirms what we have known intuitively Dr Richard Bleicher
The study was published online on May 18 in Cancer Epidemiology, Biomarkers and Prevention.
The researchers also reported that 5-year relative overall survival rates increased across all age groups.
For example, the 5-year rate among women aged 15 to 49 years who were initially diagnosed with de novo MBC doubled from 18% to 36% in the period 1992-1994 vs 2005-2012. However, the gains among other age groups between these two periods were not as dramatic.
"Even though metastatic breast cancer is incurable, in some cases we can convert metastatic disease to a chronic, long-term disease that has a good quality of life," commented Dr Bleicher.
The improvement in survival in de novo MBC is likely due to treatment and the aging of the US population, say the study authors.
However, they also say that the improvement may be partially due to changes in stage migration, because fewer stage III cancers and more stage IV cancers are being diagnosed. The shift may be the result of improved imaging, they say.
But David Mankoff, MD, a radiologist at the University of Pennsylvania in Philadelphia, was hesitant to have his specialty credited here and said the "more likely" explanation for the survival gains is improved therapeutics.
Dr Mankoff, who was asked for comment, also noted that in the absence of symptoms, imaging for the purposes of systemic staging is not generally appropriate for patients with early-stage disease.
A novel finding in the study is its estimation that, as of January 1, 2017, more than 150,000 US women were living with MBC, and that 3 of 4 had initially been diagnosed with early-stage disease.
Furthermore, the authors estimate that the number of women with MBC is growing.
They estimate that the number increased by 4% from 1990 to 2000 and by 17% from 2000 to 2010, and they project a further increase by 31% from 2010 to 2020.
These tallies are estimates because they include both de novo disease and metastatic disease that is a result of recurrence or progression of breast cancer that was initially diagnosed at an earlier stage.
The study authors explain that there are no nationally representative data that capture metastatic recurrence. This is important because the vast majority of cases are metastatic recurrences; de novo cases account for only a minority of MBCs in the United States.
However, as the study authors say, "Currently, registries in the United States do not routinely collect or report recurrence data."
That fact is "incredibly frustrating," said Beth Caldwell of Seattle, Washington, a married mother of two young children who was initially diagnosed with MBC.
The NCI goes on and on about how hard it is to collect recurrence data.Beth Caldwell
"The NCI goes on and on about how hard it is to collect recurrence data, but I have yet to hear an explanation as to why it's so hard that makes any sense. If Congress mandated that SEER include tracking of recurrences, it would, period," she told Medscape Medical News.
In a press statement that accompanied the new study, the NCI explained the lack of recurrence tracking this way: "Collecting recurrence data has been challenging for cancer registries because recurrence can be diagnosed through diverse methods and in a variety of locations."
However, the NCI also stated that it is funding pilot studies "aimed at identifying ways to leverage existing data and informatics methods to efficiently capture information on recurrent disease."
Caldwell, who said she was "happy" to see the new study, also observed that it was a long time coming and asserted that the study was prompted by activists.
"Without the advocacy of advocates ― in particular, Katherine O'Brien, of the Metastatic Breast Cancer Network ― this study never would have come to pass," said Caldwell, who has spent time as an activist.
A couple of years ago, O'Brien spearheaded the creation of an online petition on change.org calling on the NCI's SEER, the CDC, and all cancer registries to start counting all people living with MBC, including those whose early-stage disease progressed. The petition has nearly 7500 signatures.
Notably, two of the study authors, including Musa Mayer, of the Metastatic Breast Cancer Alliance, are from breast cancer advocacy organizations. Mayer is noted, among other things, for her mantra about the need to fully tally metastatic breast cancer cases in the United States: "What we don't count, we can't plan for."
The study authors, in their estimate of how many people are living with metastatic disease, applied a "back-calculation" method to breast cancer mortality and survival data from the SEER Program.
Carol DeSantis, MPH, director of Breast and Gynecological Cancer Surveillance at the American Cancer Society, who was not involved with the study, thinks the approach is sound.
"The authors make reasonable assumptions in their estimate of the number of women with MBC," she told Medscape Medical News.
"In a perfect world, registries would collect data on recurrence, but until then, the model these investigators have come up with helps give us a better sense of the prevalence of metastatic breast cancer," she said.
The study was supported by the National Cancer Institute of the National Institute of Health. The authors and commentators have disclosed no relevant financial relationships.