TORONTO, OntarioWhen performing lymphoscintigraphy in breast cancer patients, sentinel nodes are seen most clearly if patients stand and hold their arm out, Sunhee Kim, MD, a resident in radiology at Mt. Sinai Hospital, New York, reported at the 52nd Annual Meeting of the Society for Nuclear Medicine (abstracts 1314, 1315). The standing position is superior to supine, and arm out is better than arm up, she told ONI in an interview at the conference. "The arm out position produces better spatial delineation between the nodes," while standing helps separate the breast lesion from the nodes, Dr. Kim said.
There is no standard way of doing lymphoscintigraphy, and the debate on methodology is ongoing, she said. Centers vary as to whether they have patients standing or in a supine position, and whether they hold their arm in or out. There are also differences between centers regarding the amount of contrast agent used, where it is injected, and even whether or not the breast is massaged to help with drug distribution to the lymphatic system.
Dr. Kim presented two studies evaluating the visibility of sentinel nodes in 73 breast cancer patients imaged in six different positions. Patients were scanned while standing with their arm out (90° from the long axis of the body) and again with the arm up in both the anterior and lateral views. They were then scanned in a supine position, anterior view with the arm out and lateral view with the arm up. Scans were done after patients received an injection of sulphur colloid at the areolar skin junction.
The researchers counted the number of sentinel nodes that could be seen in images from each position and measured the distance between the center of the first lymph node and the breast lesion, and the distance between the center of the first node and the second node.
More sentinel lymph nodes were seen in the standing, arm out anterior view than in the supine, arm out anterior view. Similarly, the standing arm up lateral view showed more sentinel nodes than the supine arm up lateral view.
In some patients, it was difficult to distinguish two different sentinel nodes in the arm up position. But with the arm out, "we can see two different nodes very clearly," Dr. Kim said. A second sentinel node was identified in 5.5% and 12.3% of patients in the standing arm out positions (anterior and lateral views, respectively) vs 2.6% in the standing arm up position, anterior/lateral views combined.
Overall, the arm out position provided significantly better spatial delineation between nodes, in both the anterior and lateral views, making it easier to see more than one node, especially when the nodes were close together. "With the arm out, the breast lesion goes down and moves more inward, pulling the lymph node down. That’s why the two lymph nodes can be seen more easily," Dr. Kim said.
In anterior views, the standing position allowed better delineation of the breast lesion from the first node, and the first node from the second node. "If you stand, there’s gravity. It pulls down the lesion, pulls down the lymph nodes, so there is better separation between the nodes and the lesion," she said.
With better visualization comes more certainty about the number of sentinel nodes, she said. "We can report to the surgeon that we can clearly see two sentinel nodes instead of hesitating and saying we’re not sure if it’s one node or two nodes. They can harvest more confidently during the surgery. It saves time and reduces morbidity from lymph node dissection," Dr. Kim said.
Study coauthor, Josef Machac, MD, director of nuclear medicine at Mt. Sinai, said that researchers at the center have been studying methodology for lymphoscintigraphy for the past several years and have found a number of items, aside from posture, that help improve the quality of images. A key factor for improving clarity involves the site of injection of the imaging agent. At Mt. Sinai, earlier published studies have shown that the injection site makes a difference, and doctors there now routinely inject at the areolar skin junction, Dr. Machac told ONI.
The region is close to an area where there are cells that communicate closely with the lymph nodes, and act as a "superhighway" between breast cells and the lymph nodes, he said. "It’s extremely reliable in delivering the colloid into the nearest lymph node, which corresponds to where this lesion drains to," he said.