Lymphatic mapping and sentinel node biopsy, when used to determine how far the cancer has progressed into the lymph nodes, can help some patients avoid the pain and discomfort of full armpit node removal, which often causes swelling, numbness and infection.
The surgical technique hasn't been used until now in women with large breast tumors because of a lack of data proving its reliability.
But the new study from the University of North Carolina at Chapel Hill School of Medicine may provide that research evidence.
The findings, published in the September issue of the American Journal of Surgery, show that sentinel node biopsy, when performed before chemotherapy is given to shrink the tumor, is very reliable, the UNC researchers said.
The study suggests that sentinel node biopsy is an option that might benefit all women with breast cancers, said Dr. David W. Ollila, the study's lead author. Ollila is an associate professor of surgery at UNC and a member of the UNC Lineberger Comprehensive Cancer Center.
"I think any woman diagnosed with breast cancer should ask her physician what role this technique might play in her overall treatment," Ollila said.
Lymphatic mapping and sentinel lymphadenectomy before chemotherapy is the standard of care for patients with small breast cancers. But its use in large breast cancers has been controversial because of lack of reliability, he said.
"Our study indicates that women with large breast cancers can derive a benefit from the sentinel node technology just like women with small breast cancers," Ollila added.
In sentinel node biopsy, a surgeon injects the area near the tumor with a blue dye, which follows the path that tumor cells most likely would take from the tumor to the lymph nodes. The surgeon removes only the nodes that initially absorb the dye. These are thought to be the "sentinel" nodes, the nodes to which cancer cells are most likely to travel. If the biopsy finds no cancer in the sentinel nodes, then no further nodes are removed.
Subjects in the study were 21 breast cancer patients with tumors large enough in relation to the size of the breast that the breast could not be preserved.
Such patients typically receive neoadjuvant chemotherapy to shrink the tumor before surgery, to decrease chances of recurrence and, for a small number of women, to make it feasible to have a lumpectomy rather than a mastectomy.
Before neoadjuvant chemotherapy, the researchers performed sentinel node biopsy, modifying the technique slightly for larger cancers by using a larger volume of dye and more injections.
If the procedure showed disease in the sentinel node or if the tumor was larger than five centimeters, all the axillary nodes were removed, and the patient received chemotherapy and surgery. If the biopsy showed tumor-free sentinel nodes, and the tumor was less than five centimeters in diameter, no further lymph nodes were removed and the patient received chemotherapy and tumor removal.
In an average of 36 months of post-treatment follow-up, none of the patients showed progression of cancer in the lymph nodes. The sentinel node biopsy accurately predicted node involvement, with a false negative rate of 0 percent, Ollila said.
Some surgeons advocate performing sentinel node biopsy in women with large tumors only after chemotherapy to discover how much of the tumor is left behind. However, these results show that performing the procedure before treatment provides a more accurate picture of lymph node involvement, Ollila said.
"If sentinel node biopsy is done after chemotherapy, the false negative rate skyrockets," he said.
Published studies show false negative rates as high as 33 percent when the procedure is performed only after chemotherapy. False negatives may result, for example, when chemotherapy kills cancer cells in the sentinel node but not in other nodes.
"We're looking at a way in which the patient has definitive breast cancer and nodal staging before she ever undergoes chemotherapy, so we know exactly where she starts," Ollila said. "Performing this procedure before neoadjuvant chemotherapy makes it easier for the medical oncologist and the radiation oncologist to know exactly what they need to do."
Other authors of the study are UNC Lineberger and medical school faculty members Drs. Carolyn Sartor, assistant professor of radiation oncology; Lisa A. Carey, assistant professor of medicine; and Nancy Klauber-DeMore, assistant professor of surgery. Dr. Heather B. Neuman, a resident in the department of surgery, also is co-author.