Although a number of surgeons have switched from random dissection of multiple axillary nodes to sentinel node biopsy, the optimal technique for performing such a biopsy remains controversial with multiple techniques in use, noted D. Scott Lind, M.D., lead author of the retrospective study.

"With respect to treating breast cancer, we have become much, much less invasive and less radical," said Lind. "In the last century we went from radical mastectomy to learning that you can do breast-conserving therapy and can spare the patient the morbidity of taking the whole breast off, with equivalent outcomes. In the last 10 years, nearly every patient who previously would have undergone axillary dissection undergoes sentinel node biopsy. The problem is that's rapidly becoming the standard of care without a standard technique. A lot of people are doing it in different ways."

Typically, a surgeon injects a small amount of a radioactive tracer around the patient's tumor, and then locates the sentinel node with a hand-held device used to detect the tracer's path. A blue dye also is injected into the breast tissue to help visually confirm the node's location. However, surgeons continue to debate the ideal site for tracer injection, with many surgeons noting that it can be technically very difficult to inject the radiotracer directly into the area of the original tumor, according to Lind.

In the current study, an American team retrospectively studied 118 patients who were grouped into three categories based on radiotracer injection technique: One group (65) had injection into the skin over the tumor, 6 had injection into the breast tissue around the tumor, and 47 had dual injection. Overall, at least one sentinel node was identified in 98.3 percent of patients. A sentinel node was identified in 98.5 percent of patients who received injection in the skin above the tumor, 83.3 percent of those who received injection around the tumor, and 100 percent of those who received both injections.

Although the results showed that injection into the skin overlying the area of the tumor is an accurate localizing technique, dual injection increased the accuracy of identification by detecting abnormal patterns of lymph fluid drainage, something that is found in up to 20 percent of breast cancer patients, Lind said. Practitioners then could target radiation treatments accordingly, sparing radiation to unnecessary tissues.

The study's authors also questioned the need for using blue dye, which is associated with rare but serious allergic reactions. The research group has abandoned its use, although it continues to be commonly used in the U.S.

"We found that using the two injection sites allows us to reliably identify the sentinel node in the most effective fashion," Lind said. "And it probably has some advantages because we won't have to worry about patients having reactions to blue dye, and we can identify nonaxillary sites of disease that may affect treatment planning. This is particularly important with the new breast cancer staging system coming out in January, which will incorporate sentinel node results."