Recently I gave a talk in St. Petersburg, Russia discussing the place of sentinel lymph node biopsy (SLNB) in breast surgery today. As I prepared my slides, I was struck by how much breast surgery has changed in the last 25 years. We’re doing much smaller operations for breast cancer.
THE OLD PARADIGM
By 1990, breast surgery had made a great leap forward. Reliable, randomized, controlled trials had proved that, for smaller breast cancers, breast conservation therapy (BCT, often called a “lumpectomy”) gave as good survival as mastectomy.
The basic rule for breast cancer surgery had become: Remove all the cancer you can find with negative margins; then treat the rest of the breast with radiation therapy.
However, we still used axillary lymph node dissection (ALND) to obtain nodes for examination by a pathologist, because looking for cancer in nodes was the best way we had to estimate the risk that cancer might come back in the future.
If cancer was in the lymph nodes, it indicated enough risk of recurrence to justify treatment with chemotherapy and/ or hormone blocking drugs.
There was, however, already a trend to remove fewer nodes because removing fewer nodes created fewer problems with persistent arm swelling called lymphedema.
If a woman had a larger cancer, we recommended a mastectomy.
A NEW PLAN FOR LARGER CANCERS
About this time, physicians asked if giving chemotherapy before surgery — called neoadjuvant chemotherapy — might be better than giving chemotherapy after surgery. It was a good idea to try, but it turned out survival was about the same whether chemotherapy was given before or after surgery*.
There was, however, a benefit of neoadjuvant chemotherapy for large tumors. If a cancer was too large for BCT, neoadjuvant chemotherapy could make the tumor shrink enough to make BCT feasible.
At least one-third of women with large tumors had their cancer shrink enough to allow BCT. With newer treatment plans, the number of women who become eligible for BCT is greater.
REMOVING FEWER NODES
Physicians also wondered if it was necessary to remove all the axillary nodes to identify women who would benefit from chemotherapy. This led to trials of sentinel lymph node biopsy (SLNB) that injected a blue dye and/ or radioactive tracer into the breast and then followed the dye and/ or tracer to identify the sentinel node(s) most closely associated with the cancer.
If there was no cancer in the so-called “sentinel node(s)”, other nodes were left alone. Removing only the sentinel node reduced the chance of lymphedema to less than 5 percent in most studies.
IS A NEGATIVE SENTINEL NODE RELIABLE?
Or, if the sentinel node is negative, what’s the chance that cancer was present in another node and was missed?
The best way to answer this question was to follow women who had no cancer in a SLNB and did not have an ALND for that reason.
Multiple studies have found that, after a negative SLNB, cancer reoccurs in another node less than 1 percent of the time. This might sound unacceptable for cancer to reoccur in the axilla (armpit) even 1 percent of the time, until we are reminded that cancer can reoccur in the axilla even if the patient has a full ALND.
Specifically, more surgery does not always guarantee better results, which is why use of ALND dropped by almost 60 percent between 1998 and 2004.
WHEN THERE IS CANCER IN THE SENTINEL NODE
There is no consensus on whether to do a full ALND on every woman with a positive sentinel node. There is, however, a strong trend to limit ALND to women with larger amounts of cancer in the node, which means not to do ALND if there is only a little cancer in the sentinel node.
For example, a micrometastasis – a spot of cancer between 0.2 and 2.0 millimeters in a node – is uncommon. When a full ALND was done for micrometastisis, most women did not have more positive nodes. For this reason, surgeons began to omit ALND if there was only a micrometastasis. In follow up of these women, the risk of cancer reoccurring in the axilla — if they did not do an ALND — was about the same as when the sentinel node was truly negative.
More recently, a randomized trial intentionally compared doing an ALND to no ALND for women with a positive SLNB, including metastases larger than a micrometastasis. This was for women who were having radiation therapy as part of BCT. Not only was there no decrease in survival when ALND was omitted, but there was no increase in axillary recurrence of cancer even though the study included women with up to two positive nodes.
These results show that chemotherapy and radiation therapy after BCT surgery are sufficient to limit further cancer growth. This is why use of SLNB alone – even with a small amount of cancer in a node – doubled to nearly 40 percent of cases by 2004.
THE NEW PARADIGM
In 2013, if a woman has a small cancer in her breast, the recommended plan is still surgery to remove cancer, leaving the rest of the breast. This is usually combined with SLNB and radiation therapy.
In contrast, the paradigm has changed significantly for larger tumors. When the cancer is too big for BCT, biopsies are done to confirm the diagnosis, and the patient is given chemotherapy before surgery because it will often shrink the cancer to a size that will allow preserving the rest of her breast.
Neoadjuvant chemotherapy is more common, but in some cases, physicians recommend neoadjuvant hormone based treatment instead.
THE NEXT QUESTION
After neoadjuvant chemotherapy, SLNB does predict additional positive nodes well. What is not yet proven is whether SLNB is sufficiently reliable after neoadjuvant chemotherapy to omit ALND. There is no long-term data that the risk of cancer coming back in the axilla is acceptably low in the situation of a negative sentinel node after neoadjuvant drug therapy.
BREAST SURGERY FOR 2014
We’ve shifted the way we treat breast cancer. SNLB is part of the story, but one can’t talk about SLNB without also considering the role of neoadjuvant drug therapy in reducing the extent of surgery for breast cancer.
Neoadjuvant treatments have enabled us to do smaller operations for many women who are diagnosed with larger cancers.
Neoadjuvant therapy and SLNB are two parts of the same story. That’s progress!
*Breast cancer is usually present – but too small to detect – for several years before it is found. Because of this several-year time course, moving chemotherapy a month or so earlier or later is relatively minor difference compared to the much longer “life-cycle” of the cancer up to that point.