(March 11, 2009 - Insidermedicine) Dr. Gretchen Kimmick, MD, MS, discusses what she would do if she had breast cancer and was going to be evaluated with molecular testing. Dr. Kimmick is Associate Professor of Medicine at Duke University School of Medicine. She is also a medical oncologist with the multidisciplinary Breast Program at Duke University.
At the 2008 Breast Cancer Symposium in San Antonio, we spoke with Dr. Gretchen Kimmick; who is Associate Professor of Medicine at Duke University School of Medicine. Dr. Kimmick is a Medical Oncologist with the multidisciplinary Breast Program at Duke University.
What is personalized molecular treatment?
Dr. Kimmick: Every breast cancer patient is a case in herself. And we make decisions about treatment based on the person and the cancer. So we have always personalized treatment. The level of personalization is getting different because we are increasing technology. The definition of personalized medicine now involves genomics. And it’s the genes actually in the tumor that are directing personalizing cancer treatment.
How does this treatment work?
Dr. Kimmick: When a woman is diagnosed with cancer we do a biopsy of the cancer to confirm the diagnosis and that piece of tissue can be sent off for testing. And it is sent off for things like hormone receptors, HER2, and those things are unique to anybody's cancer. Now we also send it off to do genetic testing. Where they do genomics of the specific genes in the cancer. And we are trying to learn about how the expression of certain genes in cancer can make us better able to treat specific cancers in patients.
How widely available are these tests?
Dr. Kimmick: There is one that is very widely available, actually two, MammaPrint and Ocotype DX. They are gene expression profiles that help us determine the risk of cancer coming back in women who have cancers that are hormone receptor positive mostly. They help us determine risk. The risk is based on population from a clinical trial so the tests still give a risk that can't tell 100% whether someone's cancer could come back or not. But they do help us determine better what that risk is. This is based not just on a population of women with similar characteristics, but more specifically to the pattern of gene expression within the tumor.
How do the results of these test affect treatment?
Dr. Kimmick: Some women who have small cancers don't need chemotherapy. We have always struggled with trying to determine which of those women don't need chemotherapy. For example if I see a woman who is very young and she has a tumor that is low grade, hormone receptor positive, and small, maybe I don't have to give her chemotherapy which could potentially cause lifelong side effects and may not even be necessary for her. So these tests are allowing us to define level of risk a little bit more that we were able to before. So she might have an Ocotype DX or a MammaPrint sent that shows that the risk of her cancer coming back is very low. And we might decide that she doesn't need chemotherapy, which is fantastic. Or we might decide based on the result of that test that chemotherapy really is likely to help her.
Are these results applicable to other members of my family?
Dr. Kimmick: Results done on cancer cells are not transferable to other members of your family. So while it is a genetic test, it is not a germ line. The difference between the tests we do on cancer cells and gene tests we do on cells that represent the composition of your whole body. BRCA1 and BRCA2 for instance are genes that increase risk of breast cancer. Those genes when they are changed in certain ways increase a risk in a family. And those tests are done in our white cells in our blood, which are germ line cells. So they represent tissue everywhere in our body. And just happen to increase risk of breast and ovarian cancer, as well as other cancers. Whereas the genetic tests on tumors don't.
Are there any other molecular tests on the horizon?
Dr. Kimmick: I think that there are a lot of gene tests out there that are probably going to come around. They are called genetic expression profiles, and there are probably going to be a lot of them. And they will be compared and tried in different populations. So that will help us but there are also going to be specific genes that we find that tell us what treatments work, like HER2. It’s a gene that turns on the 2nd human epidermal growth factor receptor and tells us that Herceptin will work. That’s a great example of the type of tests that we are doing right now.
If I had breast cancer and was going to be evaluated with molecular testing...
Dr. Kimmick: If I had a diagnosis of breast cancer and were evaluated with genomic testing of the tumor, I would want to make sure that the cancer was in the right category to where testing was appropriate. And right now testing is appropriate in women who have hormone receptor positive, node negative breast cancers. And it helps us determine if chemotherapy is worth doing in that case.