Women with breast cancer have the greatest chance of survival if the tumor has not spread into the lymph nodes under the arm or beyond. Standard therapy for breast cancer involves removing the tumor as well as most of the underarm, or axillary, nodes to examine them for cancer cells. This procedure is associated with complications in the majority of women who have the nodes removed.

However, a new method is currently under study that finds and removes just one or a few of the "sentinel" nodes into which the tumor drains lymph fluid. The long-term effectiveness of the procedure, called sentinel lymph node biopsy is still in question, but if clinical trials prove that sentinel node biopsy can control breast cancer, it will be important to know whether the procedure can be done in smaller hospitals.

A key to the success of the procedure appears to be the training and experience of the person performing it. A new study of nearly 1,000 women with breast cancer, presented March 16, 2001, at the annual meeting of the Society of Surgical Oncology, reports that 111 trained teams consisting of surgeons, nuclear medicine physicians, and pathologists -- many of them community-based -- successfully found sentinel nodes 86 percent of the time.

This achievement suggests that sentinel node biopsy can be done effectively in all practice settings, reported Douglas Reintgen, M.D., of the Moffitt Cancer Center in Tampa, Fla. He and his team, supported by a grant from the U.S. Department of Defense, developed a two-day training course for surgeons and their colleagues in nuclear medicine and pathology from 42 institutions around the country.

The participants learned how to identify, or map, sentinel nodes using two procedures. One employs a radioactive marker that accumulates in the lymph nodes into which the tumor drains. The second procedure involves injection of a blue dye that collects in the sentinel node. Each patient's nodes were "mapped" using a combination of these procedures.

To reinforce the training after they returned home, the multidisciplinary groups were required to map the sentinel nodes and then remove all the axillary lymph nodes for their first 25 cases. The complete removal of all nodes allowed the teams to determine if they had accurately identified the sentinel nodes. After this learning phase, complete removal of the axillary nodes was not performed unless the sentinel node was positive for metastatic disease.

At Moffitt, where the surgeons had the greatest experience in the procedures, the rate of success of finding an axillary sentinel node was 93 percent. For all the other institutions in the study, the combined success rate was 85 percent. Reintgen suggested that the overall success rate, which was higher than in previous trials, may be a result of the teams training together, the learning curve involving 25 cases, and the mapping of nodes with two techniques.

"Lymphatic mapping has the potential for changing the standard of surgical care in the breast cancer population," said Reintgen.

For women with a negative sentinel node, the procedure spares them from the more extensive surgery and the resulting potential complications. These complications, seen in more than 80 percent of cases, can include lymphedema, which is an often long-lasting swelling in the arm caused by excess fluid; numbness; a persistent burning sensation; infection; and limited movement of the shoulder.

Reintgen noted that sentinel node biopsy may also change the staging system for breast cancer. What stage a cancer has progressed to determines what kind of treatment is called for. Most lymph fluid drains into the arm, and if a cancer-positive node is found there, the disease is considered Stage II.

But mapping studies show that sometimes the lymph fluid initially drains into nodes under the breast bone or in and around the collarbone. In the current staging system, when these nodes are found to be positive in complete lymph node removal, they are considered Stage III and IV, respectively. Yet, Reintgen said, metastases to these sites probably represent the same biological phenomenon and should likely be staged similarly.

Whether or not lymph nodes contain cancer cells is also a key factor in determining if a woman should have adjuvant treatment, such as chemotherapy or radiation, following surgery to remove the breast tumor.

"When the tumor is small, information on lymph node involvement is particularly crucial to making a decision about adjuvant treatment," said Jeffrey Abrams, M.D., of the National Cancer Institute's Division of Cancer Treatment and Diagnosis. "That's why the two large NCI clinical trials, which are assessing if the sentinel node procedure is comparable to the time-tested standard of complete axillary dissection in terms of cancer recurrences and overall survival, are so important."

The status of lymph node involvement is likely to gain increased clinical significance in the future as improved imaging techniques detect growing numbers of women who have small tumors.

In addition, Abrams said, by removing only one or two nodes, sentinel node biopsy may allow more detailed examination of those nodes for disease. The nodes can be thoroughly sectioned and examined and, as more molecular markers become available for staging cancers, it may become possible -- logistically and economically -- to use them routinely if they need be applied to just one or two nodes. But, for now, sentinel node biopsy remains experimental.