While washing her car, Karen Rudderow nicked her finger on the bumper and developed an infection in the cut. A course of antibiotics would have done the trick for most folks, but Rudderow is a breast cancer survivor. The finger scrape was an ill-fated one. She developed pain and swelling in her arm, a condition known as lymphedema, which is a complication of having had her lymph nodes removed. Since then, she’s had many flare-ups in her right arm, triggered by carrying plates at a fund-raiser and even by vacuuming. At these times, the pain “pounds like a migraine, and the whole inside of my arm is numb,” she describes. She’s become left-handed to maneuver in the world, wears fanny packs instead of purses, and lets others do heavy work for her. She has adjusted to these changes amiably, grateful she’s alive nearly two decades after her breast cancer diagnosis.

Many breast cancer survivors are plagued by lymphedema. That may change soon. Doctors and patients are now wrapping their eager arms around a new technique that rids women of the risk of lymphedema. Called sentinel-node biopsy, the procedure is hailed by many experts as the most important advance in breast surgery since the development of reconstruction for a mastectomy. By pinpointing and removing only one or two key “sentinel” nodes to which a tumor will first drain, doctors can find out whether or not the cancer has spread to the entire lymph-node system of 25 or so nodes. If the sentinel nodes are cancerous, the rest of the nodes must be removed. But if they’re clean, studies have shown the rest of the nodes are also cancer-free and so can stay intact.

Not surprisingly, the greater sophistication of this technique also means it’s more exacting—requiring more science, skill, and scrutiny than demanded by the traditional method of removing all nodes, called auxiliary dissection. But as more and more doctors become trained in it, the sentinel node biopsy may soon become the standard of care. And that’s hopeful news to the estimated 100,000 women a year who must have their lymph nodes checked for the spread of breast cancer.

Here’s how the new procedure works, according to sentinel-node biopsy researcher Michele Gadd, M.D., assistant professor of surgery at Massachusetts General Hospital. The doctor injects the radioactive material around the biopsy cavity or the tumor. Then, the patient is anesthetized, either partially or completely, before the blue dye is injected, which often happens the next morning. “Unlike the radioactive material, the blue dye doesn’t hang around for long,” notes Dr. Gadd.

The doctor next massages the breast for about five minutes, to push the dye into the lymph system, and a small incision is quickly made under the arm, where the sentinel nodes are located. The doctor then “maps” the nodes, looking for traces of the dye and radioactivity that will show up if the cancer has spread. Between one and three nodes are removed, and if negative, no more are taken out. But if they contain a tumor(s), the doctor will proceed to do the full dissection. And finally, the lumpectomy or mastectomy (whatever has been planned) follows.

When 46-year-old Carol Casey of Nebraska underwent her sentinel node biopsy last year, she felt a slight sting from the single injection of radioactive material. “But it wasn’t too painful,” notes this scientist and mother of three boys. Jean Reeve of Florida had a similar experience even though she received six injections. “The radiologist slipped them in so well, they hardly hurt at all,” she says. Both women rejoiced when their nodes were declared clean, and both readily trusted the results. “The cancer center here in Tampa claims a 98% accuracy rate, and that’s good enough for me,” says Reeve.

Indeed, the accuracy of the procedure is still under intense study, as doctors determine whether it can safely replace the auxiliary dissection. After all, if a doctor either misidentifies the sentinel node or misses cancer in this node (called a “false negative” result), the consequences can be disastrous. Cancer can spread, irreversibly and fatally. In general, says Dr. Gadd, the false-negative rate is about 10 percent. That figure may seem less-than-persuasive if you’re wavering about having the procedure done.

But consider this: Because of the flurry of new research and intensive training over the past year or so, there are now proven ways to improve the accuracy of sentinel node biopsy and to judge whether you can trust it. According to Peter Pressman, M.D., clinical professor of surgery at the Albert Einstein School of Medicine, attending surgeon at Lenox Hill and Beth Israel Hospitals, and author of Breast Cancer: The Complete Guide, “accuracy should approach 100% if the patients are properly selected and the team of physicians is experienced.” That means patients who have large tumors or “multi-centric” tumors (appearing in more than one area) aren’t ideal candidates for the procedure, because it’s more likely their tumors have spread to the nodes, he says. Patients who’ve had prior biopsies in which a large amount of tissue was removed should also have the traditional auxiliary dissection, since the “distortion of the breast tissue may interfere with normal lymphatic drainage, making the pattern of drainage difficult to delineate,” he adds. Due to this potential glitch, a patient who has an excisional biopsy is not as good a candidate as one who has a needle biopsy.

The second piece of the equation—the skill and experience of your surgeon and pathologist—is even more important. “The learning curve for the procedure is lessened,” says Dr. Pressman, as more surgeons become adept at doing it and share their knowledge. Also, “there’s more cooperation between surgeons and pathologists,” since the pathologist now has the trickier task of detecting limited disease. The most experienced doctors are usually found at well-known institutions, points out Dr. Pressman. “The American College of Surgical Oncology says that a surgeon has to have done 30 sentinel node biopsies before calling themselves qualified,” says Dr. Gadd.

Of course, you’re safer if the surgeon has gone beyond this threshold. “Some-where between 30 and 50 cases, I knew my ability to be accurate,” says Dr. Pressman, who has done over 100 sentinel node biopsies. Indeed, a new study by experts at the Lynn Sage Comprehen-sive Breast Cancer Center at Northwest-ern University Medical School showed that the number of cases performed by an individual surgeon was a good gauge of ability to accurately identify the sentinel nodes.

Accuracy is also boosted by a technique: The combination of two detection methods, blue dye and a radioactive isotope, is usually more successful than using either one alone. “In rare situations, only one of the methods may be preferred. For instance, if the tumor is very close to the nodes themselves, putting dye directly into that area may not be as easy to see as when you use the isotope alone,” says Dr. Pressman. But apart from these exceptions, the combination works best, as confirmed in a recent report involving 500 cases at Memorial Sloan-Kettering Cancer Center in New York City.

Enthusiasm for sentinel node biopsy is overwhelming. But amid the zeal, it’s important for doctors and patients not to “get too hung up on removing only one node,” reminds Dr. Pressman. Sometimes that’s all it takes to determine whether or not cancer has spread. But if it takes the removal of three nodes to make the same judgment, so be it. That’s still a far cry from 25 nodes, and the potential for a lifetime of discomfort.