What is the role of a sentinel lymph node biopsy in breast cancer diagnosis
Benjamin O. Anderson, MD
Professor of Surgery, University of Washington School of Medicine
Q: What is the purpose of lymph node biopsy and dissection?
A: The importance of sentinel node biopsy and complete axillary node dissection is for staging the cancer—for understanding how aggressive it is and its potential for spreading to other parts of the body. If someone dies of breast cancer, it’s actually not the cancer in the breast that’s the problem; it’s metastatic spread, where the cancer goes to other organs, that will ultimately overwhelm someone. Knowing whether the cancer is able to spread to the lymph nodes is one of the best predictors we have of the likelihood of the disease showing up in other places, and it allows us to adjust our systemic drug therapy accordingly.
Q: Is biopsy and dissection a way of treating cancer?
A: We don’t think that leaving a significant amount of cancer in the body is a good idea, and cancer does need to be treated, but we’re learning that when the volume of cancer in the lymph nodes is small or microscopic, therapies other than surgery can be effective.
Q: How has the role of sentinel lymph node biopsy changed in recent years?
A: It has been an ongoing evolution. It used to be that the only way we had to assess the lymph nodes was to remove all of them by doing a complete lymph node dissection. Because of studies begun in 1994, we’ve learned that sentinel node biopsy is a reliable way of predicting whether the rest of the nodes have cancer; so, instead of taking out all of the nodes, we take out the first few nodes to which the cancer would have spread, and if those nodes are okay, the rest should be okay. Clinical studies have validated the effectiveness of sentinel lymph node evaluation.
The evolution has continued, and the thinking has followed that if the sentinel node is positive, you need to take out the rest of the nodes both to find out how many nodes are positive and to avoid leaving significant disease behind. Another trial in 2011 showed that in patients with early-stage disease who are being treated with breast-conserving radiation and drug therapy, we can avoid removing the rest of the lymph nodes even when the sentinel node is positive.
Q: Which breast cancer patients should undergo a sentinel lymph node biopsy?
A: Currently, we’re using sentinel node biopsy in Stages I through III; the only cancer with which we’re not comfortable using sentinel node biopsy is inflammatory breast cancer. So, in the great majority of breast cancers, we’re able to use sentinel node biopsy to determine node-positive or node-negative status.
Of those patients who undergo sentinel node biopsy, there’s a subset of patients who can forgo completion of dissection, even when the sentinel node is positive. This subset consists of women with cancers smaller than 5 centimeters who will undergo breast-conserving surgery and radiation. Because we are fairly good at finding early-stage disease, that’s a fairly large group, but it’s not everybody. It is a very specific, focused group in which we have this evidence that we can stop at a sentinel node biopsy, even when it’s positive. Patients who do not fall into this category are those who have neoadjuvant chemotherapy, mastectomy patients, women who have more than two positive sentinel lymph nodes, and those who have undergone partial breast radiation (focusing only on lumpectomy site).
We want to do enough therapy without doing too much. We started with the most aggressive, biggest surgeries, and our data has shown that there is a place that’s enough without doing too much. It is possible to do too little—research in the 1990s showed us that if you do too little surgery, you have excessive recurrence rates. The sentinel node biopsy shows us that there are patients on whom you can do less surgery; but forgoing surgery or going too far can have adverse consequences, and we’re learning more about where that line is.
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