Using magnetism to target breast tumors

A stainless steel seed no bigger than a grain of rice is helping breast surgeons at Baylor St. Luke’s Medical Center remove tumors, while preserving as much healthy tissue as possible.

“Our patients face two problems with early breast cancer,” said Alastair Thompson, M.D., a Baylor St. Luke’s breast surgeon. “First, with a small, impossible-to-feel breast cancer, how do we find it in the operating room? Second, we need to identify the sentinel lymph nodes that drain the fluid coming from the cancer and sit in the armpit.”

Thompson, along with Stacey Carter, M.D., and Elizabeth Bonefas, M.D., are the first surgeons in the region to employ the Sentimag system, which uses magnetism to locate cancerous tissue in the breast and nearby lymph nodes during surgery.

Days before surgery, a radiologist will place the stainless steel seed—known as a Magseed—within the cancerous area so surgeons will be able to pinpoint the tissue to be removed in the operating room using Sentimag’s magnetic sensing probe.

“We can detect the seed with our magnetizer and identify which small area of tissue to take out,” said Thompson, section chief and professor of breast surgery at Baylor College of Medicine.

Just before operating, surgeons will also inject a dye under the nipple that contains protective coated iron oxide—known as the Magtrace marker. These tiny iron particles will enter the lymphatic system and travel to the nodes most likely to contain cancer. Surgeons can identify these nodes with the same magnetic sensing probe, which makes an increasingly high-pitched noise similar to a metal detector when it closes in on the stainless steel and iron oxide.