Page 92 - MBCA_FULL REPORT_FINAL_FOR_WEB

Data from the NCI SEER Registries

Since 1973, the SEER registries of the NCI have been collecting population-based information
on cancer cases and the initial course of treatment. These registries include 9 states, 5
metropolitan areas, and the Alaskan Native Tumor Registry. Together they represent about
28% of the entire US population, broadened in the past 20 years to offer a truly representative
cross-section of the country with regard to our ethnic, immigrant, racial, educational, and
socioeconomic diversity. Analyzing SEER data enables researchers and policy makers to
An estimated 3.1 monitor cancer trends and gather data on incidence, the extent of disease at diagnosis, initial
million women in the therapy, mortality, and survival.
US have a history
of invasive breast Unfortunately, because only incidence, initial treatment, and mortality are captured in the SEER
cancer. We have registries, and recurrent cancer is not tracked, the data on all metastatic cancers, including
no way of knowing MBC are limited.
how many of these
people are actually
living with MBC.
Incidence

The actual number of new cases of MBC diagnosed each year is unknown. This is because
SEER only records the 5% of newly diagnosed breast cancer patients who have de novo MBC.
However, most patients with MBC were first diagnosed at earlier stages of breast cancer that
then recurs, months to years later [30] . An estimated 20% to 30% of early stage breast cancer
patients will develop MBC sooner or later. The SEER registries do not capture this much larger
percentage. As a result, the actual annual incidence of MBC remains unknown.

Prevalence

The prevalence of breast cancer is increasing. Today, an estimated 3.1 million women living
in the US already have a history of invasive breast cancer, and in 2014, an estimated 232,670
women will be newly diagnosed [99] . However, we have no way of knowing how many of these
people are actually living with MBC as a chronic, progressive, and ultimately fatal disease or how
many are “cured” of the disease, meaning they will go on to die of other causes. After early stage
breast cancer is treated, it can lie dormant for as many as 20 or more years, with no way of
determining whether it is actually cured or in a temporary state where there is “no evidence of
disease.” This complicates the already challenging assessment of MBC prevalence. Neither the
total number of people living with MBC nor its burden in society can currently be determined.

Creative methods have therefore been used to estimate the prevalence of MBC. The duration
of survival of patients with MBC (itself an estimate based on data from clinical trials involving
highly selected patients), multiplied by the annual number of breast cancer deaths, has
been used to approximate MBC prevalence. Estimating survival duration is complicated by
significant variability related to the type of MBC and the treatment received. With good access
to care and favorable tumor biology, some MBC patients can live for a decade or more. Using
more sophisticated techniques, Australian biostatisticians have modeled the prevalence of
MBC using the New South Wales cancer registry, estimating the prevalence as 3 to 4 times the
number of annual deaths from breast cancer [100] . This approach is based on the fact that at
least 90% of breast cancer deaths occur as a result of complications related to MBC.
92