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Former President Jimmy Carter announced earlier today that he has been diagnosed with melanoma, the most serious form of skin cancer, which has spread to his brain.
What does this mean? Is this the same as brain cancer? If not, what’s the difference?
Cancer that begins in one spot of the body and then spreads to another – called metastasis – is called metastatic cancer.
In the unfortunate case of President Carter, his melanoma started on his skin and has metastasized to the brain, which we would refer to as “brain metastases” or “secondary brain cancer.”
What we commonly refer to simply as “brain cancer,” is cancer that actually begins in various brain cells/tissue (also sometimes referred to as “primary brain cancer.”)
Primary brain cancers and brain tumors are biologically different from brain metastases. Typically, brain metastases retain many, but not all, of the molecular characteristics of its primary cancer (i.e. if breast cancer metastasizes to the brain, the secondary tumor is made up of abnormal breast cells, not of abnormal brain cells. It is thus called metastatic breast cancer, not brain cancer.)
There is no official accounting of, and some significant disagreement regarding, the amount of cancer cases each year that metastasize to the brain. Estimates range on the low end from approximately ~56,000 cases to ~500,000 on the high-end of cancer patients developing brain metastases annually. And studies have cited that the percentage of cancer patients who will develop brain metastases is anywhere from 6-28%.
What we do know is that approximately 80% of cancers have been associated with the ability to metastasize to the brain. In addition to melanoma, like President Carter’s, the four other most common types of cancer to spread to the brain are: lung, breast, renal, and colorectal.
The types of tumors that the National Brain Tumor Society focuses mostly on are all primary brain cancers or brain tumors – glioblastoma, oligodendroglioma, astrocytoma, medulloblastoma, DIPG, meningioma, etc. However, brain metastases are an increasing area of interest for both our organization and the entire neuro-oncology field, as many areas of intersection between these tumors continue to emerge.
One area of strong overlap potential is, in fact, also related to melanoma. Much progress has been made in melanoma treatment in recent years – which has been estimated to metastasize to the brain in nearly 50% of all cases. These lessons are now being explored in brain cancer to see if they can have the same impact on patient survival.
For example, as noted in the Q&A post we did earlier this year with Dr. John Sampson of Duke, the success of early immunotherapies in treating melanoma with brain metastases has provided much of the rationale for researchers who are now studying immunotherapy for brain cancer, including a major trial announced in 2014.
Beyond the issue of metastasis, the trend toward precision medicine is also knocking down traditional borders when it comes to cancer treatments. Coincidently, stories this morning from TIME magazine and NBC News tell of a trial that has shown encouraging results using a drug developed originally for melanoma in other cancers – including glioblastoma – that have the same mutation, called BRAFV600.
We wish our very best to President Carter. Our thoughts are with him and his family today. It is our hope that many of the great strides in melanoma treatment in recent years will help him in his fight. We are also hopeful that some of these same treatments will eventually benefit brain tumor patients.