Where is the Data? The Epidemiology of Metastatic Breast Cancer

Today, we are missing important data. We don't know how many people are living with metastatic breast cancer (MBC), how many early stage breast cancer patients have recurrences, and how the incidence and outcome of MBC have changed over time for the common subtypes of breast cancer.
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Today, we are missing important data. We don't know how many people are living with metastatic breast cancer (MBC), how many early stage breast cancer patients have recurrences, and how the incidence and outcome of MBC have changed over time for the common subtypes of breast cancer.

There are 3.5 million women and men in the US that have had a history of breast cancer, but of these, we do not know how many are living with MBC today. A lack of information on the incidence and prevalence of MBC is a critical issue: it hinders an understanding of the scope of MBC and limits the ability to convey the urgency for more research and the development and deployment of support services. It is impossible to effectively advocate for this group of patients without key data about the population and the disease, for which there is no cure.

In contrast, consider the numbers that inform decisions in other critical diseases. More than 23,000 people in the mainland US and Puerto Rico have contracted the Zika virus, according to the Centers for Disease Control and Prevention (CDC), including 2,000 pregnant women. The CDC estimates 21 babies have been born with birth defects related to Zika.

How is it that we have such solid estimates, and nuanced details, of a new health threat but we don't have accurate statistics on a disease that kills 41,000 women and 500 men each year in the US?

The Metastatic Breast Cancer (MBC) Alliance is a coalition of more than 40 groups and individuals including nonprofit organizations, people living with MBC, pharmaceutical companies and advocates working together to make advances against MBC and address the needs of MBC patients. Our 2014 Landscape Analysis report highlighted key missing information about the epidemiology of metastatic breast cancer.

Key unanswered questions related to the epidemiology of MBC are:
  1. Prevalence: How many people with MBC are alive today? Is prevalence changing over time? What proportion of patients are diagnosed first with Stage IV de novo disease versus those whose disease recurs as MBC months to years after their initial treatment?
  2. Incidence: How many early stage patients go on to experience distant metastatic recurrence of breast cancer? Does incidence vary by tumor type or stage at diagnosis, and what is the median time to recurrence?
  3. Outcomes: How does outcome (length of survival) of MBC vary by tumor subtype, by de novo versus recurrent disease? Have new treatments impacted outcome? What is the quality of life of people with MBC, and how does treatment affect these issues?
In October 2016, the MBC Alliance launched a new campaign,
. The objectives are to:
  • Broaden the public's understanding of MBC;
  • Provide facts about this incurable disease and share personal stories from those living with MBC;
  • Encourage the public to sign a petition urging Congress to give our national cancer registries, including the NCI SEER and CDC National Program of Cancer registries, the mandate and necessary funding to collect accurate statistics for those living with metastatic breast cancer.

The MBC Alliance does more than urge Congress, or others, to solve these challenges. The Alliance is actively working with NCI's Surveillance, Epidemiology, and End Results (SEER) Program and with state-level and individual hospital cancer registries to understand these issues and work collaboratively towards solutions. Epidemiologists at NCI SEER are developing better estimates of incidence, prevalence and outcomes of MBC by utilizing sophisticated statistical modeling techniques that have been effectively used at individual hospitals and in other countries. The aim is to better estimate both the numbers of MBC patients in the US and MBC outcomes as they change over time. In concert with this effort, the MBC Alliance and the NCI SEER registry leadership, in partnership with the American Cancer Society, are developing tools to study quality of life at the population level and understand patient-reported outcomes and patient-generated quality of life data.

Capturing actual data on MBC recurrence and outcomes is particularly challenging as recurrences often occur many years after treatment for early stage breast cancer is completed. Once cancer treatment is completed, many patients return to their primary care physician and are not actively monitored by their cancer care team. Over the course of time, between when treatment ends and a recurrence occurs, which can be five or more years, a patient may have moved away from her/his oncologist where the primary cancer was treated.

Even when a patient is under the care of the cancer center where they were initially treated, recurrences may not be easily identified. For example, a patient might experience pain in her joints or bones, but if many years have elapsed since diagnosis, medical professionals may think first of a sports injury, arthritis or just plain aging. It is only when a scan reveals metastatic cancer in the bone that a recurrence is identified.

These are examples of how complicated it can be to track recurrences of breast cancer among the 3.5 million women and men in the US alive today with a history of breast cancer. Yet over time, an estimated 20 to 30 percent of these patients will eventually experience a metastatic recurrence. With 250,000 new breast cancer cases every year, the tasks of tracking recurrence, outcomes and quality of life is daunting and the current healthcare systems in place in the US are simply not designed to track recurrent disease.

Existing cancer registries were designed in an era when MBC patients--and indeed people with all forms of metastatic cancers--did not live more than a few months. Today, advances in medicine can prolong the life of patients with metastatic cancers for many years, and thus changes in cancer registries are increasingly important. The National Cancer Moonshot, "big data" efforts in cancer genomics and research and a move towards standards for electronic medical records may make it possible to one day to track the entire course of MBC and other diseases, including incidence, treatment and outcome information. In the meantime, improvements in existing cancer registries will illuminate key information about metastatic cancers.

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