TAMPA, Fla--Sentinel lymph node evaluation can eliminate the need for total axillary dissection in 75% of breast cancer patients, Alan Shons, MD, said at the 20th Annual San Antonio Breast Cancer Symposium.
This conclusion comes from a series of 243 patients at the H. Lee Moffitt Cancer Center; the sentinel node was identified in 224 cases and was positive in 54 cases.
There was one false-negative finding, which Dr. Shons called a "skip" metastasis, meaning that the cancer cells bypassed the sentinel node and were found in an adjacent node. Complete axillary dissection performed in 156 patients revealed no other cancerous nodes in patients who had negative sentinel nodes.
The series also showed that even small tumors have metastatic potential that warrants evaluation of the sentinel lymph node, said Dr. Shons, a surgical oncologist at the University of South Florida H. Lee Moffitt Cancer Center.
Up to 3 hours preoperatively, technetium-labeled sulfacolloid solution is injected, which allows for a lymphoscintigram. Then 5 to 10 minutes prior to surgical preparation, a blue dye is injected around the tumor or biopsy cavity.
"The preoperative lymphoscintigram may be helpful in some cases, but the location of the incision in the axilla has become a standard location, so I dont think lymphoscintigraphy is really necessary," Dr. Shons said.
If the patient has a lumpectomy, the tumor is removed and an incision is made in the axilla to look for a blue lymphatic that leads to the blue-stained sentinel node. A gamma probe can be used for confirmation. For mastectomy patients, the specimen is reflective of the chest wall, revealing the lymphatic that leads to the blue-colored sentinel node.
Intraoperatively, the sentinel node is evaluated by imprint cytology. Postoperatively, the node is submitted for permanent analysis and cytokeratin immunostaining.
"If the imprint cytology is positive, we proceed immediately with axillary dissection," Dr. Shons said. "If the cytology is negative, we do nothing more with the axilla at that time. If the postoperative evaluation comes back positive, the patient then returns for a delayed axillary dissection."
In the 243-patient series, the likelihood of nodal metastasis increased with tumor size, but even some small tumors were associated with metastasis. Of 54 patients who had tumors ranging in size from 0.1 to 1 cm, six had positive sentinel lymph nodes (see table).
Of the 55 patients with metastatic disease, the disease had not spread beyond the sentinel node in 26. Additionally, Dr. Shons and his colleagues found positive sentinel nodes in two patients who had histologically proven ductal carcinoma in situ (DCIS).
In a previous series involving 397 sentinel lymph node evaluations, the addition of cytokeratin staining upstaged 35 patients by identifying micrometastases that were missed by imprint cytology. Moreover, 28 of the 35 nodes appeared negative by permanent histology.
"The bottom line," he said, "is that we were able to upstage about 10% of the patients who, by normal techniques, would be considered to have negative nodes."