Physicians once 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 can occasionally leave women with permanent, disabling swelling.
In a new 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 where the sentinel node is cancerous, further node surgery is needed, as well as aggressive chemotherapy.
Sentinel node biopsy is already 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 less side effects, a lot less discomfort, and they heal quicker,” said Hiram Cody III, 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-size nodes, which are packed with disease-fighting white blood cells, work to filter impurities.
Other researchers substituted a radio- active 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 are now 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 even 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, it has proved 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, we can now 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 is offering sentinel node biopsy alone to patients with tumors smaller than 2 centimeters.
“Nothing is 100 percent accurate,” said surgeon Cody. “We feel the likelihood of missing something is extremely small in this group.”
But because the stakes are higher with breast cancer than 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–or 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.
