The Silver Bullet, and not the one the Lone Ranger carried, is a drug that goes specifically and only to a breast cancer cell to kill it. We have had some not so perfect silver bullets in the past, but newer target therapies are turning out to act like silver bullets should. But first, a review.
Cancer cells exhibit uncontrolled growth in that they grow anywhere and everywhere. Imagine you are baking a cake and you pour the batter into a pan to shape the cake. After baking, you expect a cake in the shape of your pan. But now imagine that the cake grew right through the pan, that is, the cake did not respect the walls of your pan but grew right through the pan and into the walls of the oven. This is what cancer does.
So, how do we stop the growth of cancer. First, you cut out the cancer much like you clean the oven. Then you attack the cancer with chemicals, only Mr. Clean won’t kill cancer. We must use chemotherapy, a set of drugs that kills cancer indiscriminately. As such, not all chemotherapies work for all cancers with some recipes working better for certain cancers and other recipes working against other cancers. The problem is that we get sick too, as some of our healthy cells also get killed by the chemotherapy.
In the 1950s, researchers identified targeted therapies for both prostate and breast cancer. These findings were lead by Charles Huggins, a surgeon from the University of Chicago, who later won a Nobel Prize in Medicine for these discoveries. Dr. Huggins discovered that the breast cancer can grow in response to estrogen stimulation and that by blocking estrogen, these breast cancers can shrink and die, that is you could starve an estrogen-fed breast cancer to death. The era of targeted therapies was born. Cancers no longer had to be treated with a shotgun approach, instead a targeted therapy to the cancer itself could be used.
In breast cancer, first there was tamoxifen and then the aromatase inhibitors to treat estrogen-fed (ER-positive) breast cancers. Then in the early 2000s, Herceptin became a targeted therapy for breast cancers that have the Her2 receptor. And while the estrogen blockers affected the whole body, Her2 tended to have limited side effects and was real close to being a SIlver Bullet. Now we are coupling a chemotherapy agent to Herceptin for a truly SIlver Bullet that is very effective and has very few side effects, i.e. it kills cancer but not you.
There is still a large group of breast cancers that do not have receptors to estrogen or to Her2, meaning there is a group of breast cancers that grow intrinsically and do not need to be stimulated by estrogen or Her2 to grow. These tumors are known as Triple Negative Breast Cancer, because they do not have a receptor for estrogen, progesterone or Her2.
Triple Negative Breast Cancers are very aggressive. Some will respond to treatment, but for those that do not, we need other options. In another post, we will discuss targeted therapies for those women with Triple Negative Breast Cancers and specifically those who also carry the BRCA mutation or the Breast Cancer Gene.