Sentinel Lymph Node Studies Considered Practice-Changing

In two separate early-stage breast cancer studies, researchers examined the benefit of testing for traveling cancer cells that may have broken off the tumor site and additional surgery if those roaming cells were found.

For patients who do not have an enlarged, underarm lymph node that can be felt on examination, surgeons will often remove the node most likely to drain the tumor site, called the sentinel lymph node. They then examine it for cancer cells from the tumor. If cancer cells are present, the surgeon may go in and remove additional lymph nodes to reduce the spread of cancer—a process called axillary lymph node dissection (ALND). However, in some cases, the sentinel lymph node is clean, but there may be additional involved nodes left behind. Surgeons are hesitant to perform the procedure across the board, though, because ALND increases the risk of long-term arm swelling, a condition called lymphedema, as well as pain and risk of infection.

In one study, researchers found that the common practice of ALND after a positive sentinel lymph node may not confer any survival or recurrence advantage. After examining 991 women who had a positive sentinel node and then randomizing them to either ALND or no ALND, researchers found that after a median of six years follow-up, there was no survival advantage to the procedure. The five-year overall survival for both groups hovered around 92 percent. The disease-free survival and local recurrence rates were also similar in each group. Investigators concluded that ALND should no longer be common practice for some patients who have clinically node-negative disease and will receive radiation and chemotherapy, due to the long-term side effects of ALND.

In the other study, researchers wondered whether using more sensitive techniques, namely immunohistochemistry (IHC), to look for stray cancer cells in the sentinel lymph node and bone marrow, could better predict individuals who are higher risk for metastases. Researchers examined sentinel lymph nodes and bone marrow from 5,539 women who underwent lumpectomies for early-stage breast cancer. Using standard histology, 23.9 percent of patients were found to have positive sentinel lymph nodes. Using the more sensitive IHC, researchers found an additional 10.5 percent of patients to have cancer in their sentinel lymph nodes. Although IHC found additional micrometastases, survival at five years was similar in both groups—95.1 percent with IHC-detected micrometastases compared with 92.8 percent with standard pathology. When researchers examined patients’ bone marrow, they found another 3 percent with micrometastases. At five years, 90.2 of women with IHC-detected micrometastases in their bone marrow were alive compared with 95.1 percent of women with no micrometastases. However, William C. Wood, MD, of Emory University, who gave the discussion after the study presentation, noted that while bone marrow metastases predicts a higher risk of death, it doesn’t offer additional information that can be used for treatment decisions.