On April 17, the FDA approved a new drug called Tukysa (tucatinib) for use in combination with chemotherapy for patients with HER2-positive breast cancer that has metastasized to the brain.
All new treatment options are good news, but this is particularly good news because:
- HER2-positive breast cancer is not as common as HER2-negative, thankfully, because it tends to spread and grow faster than its negative counterpart;
- Clinical trials often exclude patients whose cancer has spread to the brain.
According to the US National Cancer Institute:
“The approval applies to patients whose cancer has spread to the brain, which occurs in more than 25% of people with metastatic HER2-positive breast cancer and is typically very difficult to treat.”
Bone and brain metastasis
Breast cancer and other cancers that metastasize often go to the bones, including the spine, which is an expressway to the brain.
As noted already, HER2-positive breast cancer tends to spread and grow faster than HER2-negative breast cancer. Cancer cells that are HER2 negative, which is my status, tend to grow more slowly. They are also less likely to recur or metastasize, though clearly my cancer didn’t get that memo.
As somebody with bone metastasis in the spine (here’s looking at you, T12), the thought of further metastases along that column, or the collapse of the vertebrae itself, is frightening. To any one with brain metastases, you have my deepest respect, most urgent prayers, and virtual showering of love.
The longhand for HER2 shorthand
HER2 is a much faster, easier way to say human epidermal growth factor receptor 2.
HER2 plays a big role in regulating cell growth and cell-to-cell communication, including a role in the development of breast cancer cells. The HER2 gene makes HER2 proteins, which are receptors on the surface of breast cells that under normal conditions control how a healthy breast cell grows, divides, and repairs itself. Under abnormal conditions, the HER2 gene makes too many copies of itself—another example of too much of a good thing becoming a bad thing, like too much wine or ice cream.
Extra HER2 genes don’t just sit around with nothing to do; they cause breast cells to grow and divide uncontrollably. The medical and scientific communities label this gene amplification and protein overexpression.
Positive and negative status can change
It turns out that positive can become negative over time and vice versa. Also, test results are sometimes borderline, and it is also possible for one area of breast cancer tissue to test positive and another area to be negative. In these or other gray-area situations, oncologists can have tissue samples retested to gain clarity, because treatment options vary between them.
HR is HER2’s BFF
I would be remiss talking about HER2 status without mentioning HR—hormone receptor—status. One of the first things every oncologist probably explains to patients with breast cancer is their HER2 and HR status. HR usually is described as either ER for estrogen receptive or PR for progesterone receptive. Like their BFF HER2, hormone receptors can also be positive or negative. And they are BFFs because they always go together.
I’ll do my best to explain HR status in plain English in another post. Meanwhile, the advances made in understanding the effects of hormones and human epidermal growth factor are good news.
The more treatment options, the better
HER2-targeted treatments can be highly effective. Even in the more aggressive HER2 positive cancers, the prognosis can be good, thank you modern medicine. More treatment options deliver more ways to address the unique aspects of every cancer.
For anyone with a cancer diagnosis that fits the profile for this new treatment, you now have another weapon to fight your battle. If the trial is not offered to you, ask—always ask.
May there soon be only one HER2 status—neutral.