Predicting the Course of Metastatic Breast Cancer: Not a Simple Path
Suppose a mathematician could tell you the chances that your cancer would spread and how long you are likely to live if it does metastasize? Would you want to know? Metastasis, becoming Stage 4, is what every cancer patient fears when she first hears her diagnosis. A new mathematical model could give you more specific information about your prognosis.
Fiction vs. fact
“The cancer has spread. There’s nothing we can do.” That’s the script of every tearjerker cancer novel and movie. In the movie version, a montage shows a few sun-lit weeks of our heroine doing what she loves best accompanied by glorious background music. Then she lies in her hospital bed looking lovely, if a bit pale, as her family says goodbye. The end.
The facts are quite different. For most metastatic patients, the doctors can do something. Stage 4 patients can live productive lives for years. Yes, the vast majority will be in treatment forever with doctors’ appointments challenging their ability to hold down a regular job; however, many manage to find the time and energy for what is most important to them. However, there is also a darker side the movies don't show. Unlike the fictional version, the path to death often is marked by increasing pain and disability, not a quick transition.
Another fact missing from the information we get from both the media and our doctors is that the site of the metastasis determines both the length of survival and the quality of life for the patient.
Researchers at the University of Southern California used computer programming and statistical modeling to view all the different ways breast cancer can spread and what influence that site had on survival. They looked at the records of 446 patients at Sloan Kettering Memorial Hospital who had no metastasis when they were diagnosed, but who eventually reached Stage 4. They tracked the progress of the cancer’s spread over a ten year period or until the patient died. They sorted out this information for all the patients regardless of subtype and then looked at it again based on the patients’ hormonal receptor and HER2 status.
They used a model called a spatiotemporal progression diagram that looks like a series of color-coded concentric circles showing the pathways that the cancers spread. The model predicts survival based on the pattern of disease progression.
Many of their findings will be encouraging to patients who worry about becoming Stage 4 or who just found out that they have a metastasis to a single site. They found that about two-thirds of the patients lived ten years if their metastasis was to a single site. And site mattered. Ninety percent of patients whose cancer spread from breast to bone were still alive five years later compared to twenty percent of those whose first metastasis site was the brain. Fortunately, bone is the most common site for metastasis while it is unusual for breast cancer to go first to the brain. About two-thirds of the women who had a single-site metastasis to the lung were still alive at the end of the ten year period studied. Not surprisingly, the more organs involved at the time metastasis was diagnosed, the worse the prognosis.
I personally would have found this kind of information helpful to me when I was diagnosed. I knew that the majority of people diagnosed with inflammatory breast cancer would become Stage 4 within two years. Although I feared dying, I feared even more that a metastasis to my brain would affect my thinking. If I had seen the chart for HER2 positive patients, I could have spent much less energy on that worry. Only a tiny fraction of people with my type of cancer have a first or even second metastasis to the brain.
No more stereotypes
It’s vital to keep in mind that this model is based on 446 women at a specific hospital between 1975 and 2009. Treatment for metastatic breast cancer has advanced since their diagnosis. It will be important to know if similar results occur with a larger sample from a wider distribution of institutions. But this information is important in changing our thinking away from a one-scenario-fits-all model.
Our perceptions of Stage IV patients are molded by our experience with a friend or family member. If we know someone who has held down a job for the last six years missing work only for doctors’ appointments, we tend to think of metastatic breast cancer as a treatable condition. If we watched our mother decline quickly, unable to find enough breath to hold a grandchild, we hear a diagnosis of Stage IV very differently.
This math model shows us that our perceptions are stereotypes. Of 350 patients in one of the models, there were 207 distinct pathways that breast cancer spread. Each of those pathways came with a different set of symptoms and a different life expectancy.
Although we hear sad stories every day about breast cancer deaths, when we are in the doctor’s office for ourselves or a loved one, we need to ask more questions about our specific situation. We need to understand how our disease is similar or different from that of another Stage 4 sister. Then with appropriate facts, we can make plans.
See more helpful articles:
Newton, P. et al. Spatiotemporal progression of metastatic breast cancer: a Markov chain model highlighting the role of early metastatic sites. npj Breast Cancer. October 21, 2015. Accessed from http://www.nature.com/articles/npjbcancer201518#f1 January 26, 2016.
Pham, X. Math Model of Breast Cancer Metastasis Predicts Survival. Labroots. November 25, 2015. Accessed from http://www.labroots.com/trending/id/1981/math-model-of-breast-cancer-metastasis-predicts-survival/clinical-and-molecular-dx January 26, 2016.