Following a metastatic breast cancer diagnosis, what tests are essential? Dr. Lisa Flaum reviews the role of key tests, and the impact of molecular (genetic) test results on treatment decisions.
Dr. Lisa Flaum is a Medical Oncologist at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University. Learn more here.
When someone has either a diagnosis or a suspected diagnosis of metastatic cancer, meaning a diagnosis of cancer that has spread somewhere outside of the breast. And the most important initial step is establishing a tissue diagnosis. So, we could have our suspicions based on imaging, based on symptoms, but the most important thing is to confirm it. And usually that confirmation involves some type of tissue biopsy. So, collecting cells, examining them under the microscope, making sure that the diagnosis in fact, is cancer. Making sure that the cancer has spread from the breast, which is something that is definable under the microscope for the most part. And then evaluating various molecular markers within the tumor itself that are critical to guiding treatment.
So, in addition to the tissue diagnosis, the other important first step is what we call cancer staging. So, establishing the extent of the tumor within the body, which typically involves some type of scans, which may be variable depending on the situation or depending on the physician often could be a CT scan and a bone scan, maybe a PET scan. There may be an MRI.
So, a number of different tests that help us establish where the tumor is at baseline, so we can better understand the anatomy, but also to follow down the road to establish whether any given treatment is working. There are also maybe discussions of other types of molecular testing beyond what we determined in terms of the traditional biologic markers. You might hear the terms next generation sequencing tests like Foundation, Guardant, Tempus, which better define the cancer’s biology, which increasingly is becoming useful in terms of targeting treatment to someone’s specific cancer.
So, the molecular tests are looking at a few different things. So, first and foremost from a breast cancer standpoint, the most important basic molecular markers are what we consider to be the four main receptors, which is the estrogen and progesterone receptor, which dictates whether a given tumor is driven by estrogen and importantly dictates whether anti-estrogen therapy is going to be an appropriate component of the treatment. The other basic marker is called HER2, which is a protein that’s over-expressed.
In about 20% of breast cancer patient cells, and it’s also very critical in terms of guiding treatment. For specific types of breast cancer, once we know those preliminary molecular markers, then there’s an array of other types of anomalies within the tumor itself that could help to guide specific treatment. So, a couple of examples, and I can talk about that when you talk about treatment. If someone has a genetic predisposition to breast cancer with a BRCA mutation, there’s a specific treatment that might be appropriate. More recently, there’s another abnormality that can be detected by these tests called a PI3-Kinase mutation that identifies a population of patients who could be appropriate for another type of targeted therapy. So, for an individual, knowing what their particular profile is, whether or not those treatments are going to be indicated right at the beginning of treatment or maybe something that we use down the road. Inevitably, they’re going to help us understand what our tools are when we’re helping to make those decisions.