Virginia Commonwealth University Massey Cancer Center is the first in the state of Virginia to use an FDA-approved substance called Magtrace that allows surgeons to spare the lymph nodes in the vast majority of early-stage breast cancer patients, reducing their risk of developing lymphedema – a complication where fluid painfully and conspicuously accumulates in the arm – months or years later.
More than 90 percent of patients diagnosed with Stage 0 breast cancer, called ductal carcinoma in situ (DCIS), have noninvasive tumors confined within the milk ducts. The challenge is in identifying the small minority of patients who do have a malignancy that has broken out of the ducts, while also leaving open the option to take as few lymph nodes as possible.
“The removal of someone’s lymph nodes follows them for the rest of their lives,” said Massey chief of breast surgery and surgical leader of the breast health team Kandace McGuire, M.D., who was the first doctor in Virginia to use Magtrace. “I want my patients to both survive breast cancer and live their best lives. If I can help preserve their lymph nodes, that’s really exciting for me.”
It used to be the case that patients with DCIS, who make up 20 percent of all breast cancer cases, would have all of their lymph nodes removed at the time of mastectomy or lumpectomy to check for invasive cancer. But this procedure carries a 20-30 percent risk of lymphedema, so nowadays the National Comprehensive Cancer Network recommends that surgeons strive to remove only what’s referred to as the “sentinel nodes,” which are the lymph nodes that drain the breast, and therefore the most likely suspects for cancerous spread in DCIS.
Removing only the sentinel nodes reduces the risk of lymphedema to 5-17 percent, but that’s still an unnecessary risk for the vast majority of DCIS patients.
Surgeons typically identify the sentinel nodes by injecting a combination of dyes into the breast. The dyes trace the path the cancer would travel if it left the ducts, straight to the sentinel nodes.
While the older dyes on the market are certainly useful, there are a few problems. Some patients have life-threatening allergic reactions to a type of dye called isosulfan, and another type of dye called methylene blue can cause skin necrosis. Additionally, to improve accuracy, clinicians added a dye that’s radioactive, meaning it can only be administered in specialized clinics, which creates barriers to access.
Magtrace is a newer kind of dye, made of iron oxide nanoparticles, that can be injected anywhere surgery is performed, and there’s no evidence for allergic reaction or necrosis. What makes this dye especially advantageous, though, is that the iron oxide particles are much larger than the dyes of the past, so Magtrace sticks around in the lymph nodes for weeks rather than hours.
That property allows doctors to inject Magtrace before performing mastectomy and then use the pathology report from the removed breast tissue to decide whether to biopsy the sentinel nodes.
If the cancer is deemed non-invasive, patients can safely keep their nodes intact, but if there’s a concern that the cancer has spread beyond the breast, the Magtrace dye is still there in the sentinel nodes to guide a biopsy.
The earlier dyes were so fleeting that there wasn’t time to get the pathology report before the dye left the lymph nodes, and once the mastectomy is done, there’s no chance to inject a second round of dye to identify the sentinel nodes.
“If you remove the breast and find out later that the patient has invasive cancer, you can’t go back and do this minimally invasive procedure later,” said McGuire, who is also a professor of surgery at the VCU School of Medicine.
According to a study involving 189 Swedish women with DCIS, Magtrace allowed about 80% of them to avoid sentinel node biopsies.
Magtrace does carry the potential for skin discoloration, where the brownish dye is visible through the skin for several weeks to months, but as clinicians become more skilled with the procedure they learn how to inject into the “sweet spot” that avoids this issue, McGuire said.
Since the dye is magnetic and designed to hang around in the body for a long time, Magtrace can also interfere with MRI scans more than a year after the injection. But according to McGuire, the value of MRI after curative breast surgery is limited, so there isn’t much cause for concern. A small study also suggests that there are ways to tweak the MRI parameters to get around the artifacts caused by the lingering magnetic particles.
Also, Magtrace is only FDA-approved for patients who undergo full mastectomy, so those in the U.S. who opt for the less aggressive lumpectomy route to treat DCIS can’t take advantage of this technology.
Finally, while McGuire serves on the strategic advisory board for Mammotome, which distributes Magtrace in North America, she does not stand to gain financially from the product.
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