Kathy D. Miller, MD; Larry Norton, MD


June 10, 2013

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Kathy D. Miller, MD: Hello. I am Kathy Miller, Associate Professor of Medicine at Indiana University School of Medicine in Indianapolis. Welcome to Medscape Oncology, Insights on Breast Cancer, coming to you from the 2013 Annual Meeting of the American Society of Clinical Oncology (ASCO®). Today I am honored to be joined by Dr. Larry Norton, Professor at the Weill Cornell Medical College and Deputy Physician-in-Chief of Breast Cancer Programs at the Memorial Sloan-Kettering Cancer Center in New York.

How Cancer Cells Set Up Shop in the Axilla

Dr. Miller: Let's start with local therapy.We saw another important phase 3 study[1] in local therapy this year that looked at women who had a positive sentinel node and randomly assigned them to additional axillary surgery or focused axillary radiation, extending to a dedicated axillary field. In this day and age, who still needs a full axillary dissection?

Larry Norton, MD: It is a very interesting topic because it has 2 parts. One is the practical aspect of how to take care of patients. The other part is the theoretical consideration. When I was in medical school, we knew how breast cancer spread. It gained access to the lymphatics, and the lymphatics took it to the axilla. The axilla acts as a filter. It broke through the filter to the rest of the body. That was always the concept behind a radical mastectomy: that you remove everything, getting all of the cells out, so that they don't spread to any other part of the body. Starting with the work of Bernie Fisher[2] and all of the work of the National Surgical Adjuvant Breast and Bowel Project,[3]and the evolution of thought about the anatomy of metastases, clearly that is not what happens. The simple linear-flow concept of how breast cancer spreads is not really applicable.

On the other hand, we know that there is a linear flow, because that is what sentinel mapping tells us. With sentinel mapping, we know which node is picking up the drainage from the breast, and if that is clean, it is unlikely that any other nodes are positive. We have this complicated biological problem that can be sorted out with site-specific metastases. Cancer cells don't go somewhere because of mechanical pressures. They probably have access to the entire body, and what matters is where they form colonies and stay, which in turn depends on the microenvironment.

There is a signal in the cancer cell -- a signature. We know a lot about that signature already, but we are learning more. It tells the cells that they can set up shop in the axilla. That carries some prognostic significance, but those genes don't overlap very well with genes that determine metastases to the lung, brain, or bone. There are separate gene sets with some overlap. The significance and control of the axilla from a theoretical point of view is not as simple as what we were taught in medical school, and that guided surgical decision-making for a very long time.


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