Not many years ago, physicians believed cutting off a woman’s breast was the best way to save her from cancer, even if only a tiny lump of breast tissue was diseased.
That approach fell into disfavor after rigorous studies proved that breast-conserving lumpectomy, followed by radiation, is as effective as mastectomy for women with early-stage cancer.
Now, surgeons are hoping to become even more discriminating with their scalpels: They want to spare not only the breast, but lymph nodes as well.
As a standard part of breast cancer surgery, the doctor cuts out at least a dozen lymph nodes from the armpit so they can be examined for any microscopic spread of cancer - even though only 20 percent of patients have cancerous nodes. It’s an invasive and painful operation that occasionally can leave women with permanent, disabling swelling.
In an experimental procedure, doctors are using a radioactive tracer to zero in on what is known as the “sentinel” node - the first destination of cancer cells shed by a breast tumor. The technique exploits the fact that foreign particles migrate through the lymphatic system in a set sequence.
If the sentinel lymph node in the sequence is cancer-free, other nodes are almost sure to be, making their removal unnecessary.
In the minority of cases in which the sentinel node is cancerous, further lymph node surgery is needed, as well as aggressive chemotherapy.
Sentinel node biopsy already is widely used for melanoma, a deadly form of skin cancer, and is being looked at for treatment of colon and prostate cancers.
“Patients have a lot fewer side effects, a lot less discomfort, and they heal quicker,” said Hiram S. Cody 3rd, a breast surgeon at Memorial Sloan-Kettering Cancer Center in New York.
“The procedure can be done under local anesthesia, and the patient can go home that day. I think it will be adopted very rapidly (for breast cancer). There’s lots of interest in it all over.”
Sentinel node biopsy was pioneered in the early 1990s after melanoma expert Donald Morton, director of the John Wayne Cancer Institute in Santa Monica, Calif., showed he could trace the flow of the lymphatic system by injecting special dyes at the site of a melanoma tumor.
The lymphatic system - a maze-like network of vessels, ducts and organs - carries a colorless fluid, called lymph, from tissues to the bloodstream. The lima-bean-sized nodes, which are packed with disease-fighting white blood cells, work to filter impurities.
Other researchers substituted a radioactive material for Morton’s tracing dye which, when used with a radiation meter, provides an audible clue about where to cut the skin. Both the radioisotope and dye now are used by surgeons, sometimes in combination.
Even so, finding the first destination of cancer cells can be tricky. The sentinel is not necessarily the node closest to a tumor. It may be a pair of nodes. A centrally located melanoma may spread to a sentinel node on each side of the body. And, for reasons that are unclear, a sentinel node simply can’t be found in about 5 percent of patients.
In studies of melanoma patients who received both sentinel node biopsy and regular lymph node surgery, sentinel nodes accurately revealed whether cancer had spread in all but a few cases. At Fox Chase Cancer Center, for example, sentinel node biopsy has proved to be 97 percent accurate.
“This is state of the art and should be done in every patient,” said Burton Eisenberg, chairman of surgical oncology at Fox Chase. “Rather than simply subject everyone to an operation which we’re not sure they need, now we can selectively subject them to an operation that is more precise.”
Recent studies of breast cancer patients suggest the procedure is just as reliable for them. For example, Memorial Sloan-Kettering found that the method missed only one cancer among 48 patients with tumors smaller than 2 centimeters; it missed two cancers among 12 patients with tumors larger than 2 centimeters.
Based on these results, Memorial Sloan-Kettering now is offering sentinel node biopsy alone to patients with tumors smaller than 2 centimeters.
“Nothing is 100 percent accurate,” said breast surgeon Cody. “But we feel the likelihood of missing something is extremely small in this group.”
But because the stakes are higher with breast cancer than with melanoma, other surgeons want more data.
With melanoma, sentinel node biopsy ends the agonizing choice between guessing which nodes to cut out - several node clusters might be near a tumor - and watching and waiting, another acceptable approach.
With breast cancer, the vulnerable lymph nodes are obvious - and finding cancer there as soon as possible is crucial to survival. The condition of the nodes helps surgeons select from an arsenal of powerful chemotherapies.
“The single most important variable in how breast cancer patients are going to do,” said Thomas G. Frazier, a surgical oncologist at Bryn Mawr Hospital near Philadelphia, “is what their nodes show.”
So far, a study Frazier is leading has found sentinel node biopsy 97 percent accurate, he said. The goal is to do the new procedure, verified by standard node surgery, on 50 patients, then decide whether to offer the procedure alone.
Meanwhile, the University of Vermont, a leader in the technique, has proposed the ultimate test: a study in which breast cancer patients randomly would be assigned to receive sentinel node biopsy or standard node surgery, then would be followed to compare their survival rates.
A randomized trial is what convinced the medical community that lumpectomy is as effective as mastectomy.
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