It has become the standard of care in treating breast cancer, melanoma and vulvar cancers, and MD Anderson surgeons are leading clinical studies to apply the technique to treat other cancers, including cervical, uterine and head and neck cancers. But the technique isn’t effective in all women with endometrial and cervical cancers — particularly patients who are obese. MD Anderson gynecologic oncologist Michael Frumovitz, M.D., led a study known as FILM (Fluorescence Imaging for Lymphatic Mapping and published in The Lancet) that highlights a way to improve sentinel node biopsy for all patients, including those with a higher body mass index.
Sentinel Node Biopsy — benefits and limitations
During sentinel node biopsies, surgeons inject a dye(s) into the lymphatic system near the tumor site. They’re able to see the dye travel through the chain of lymph nodes and more easily determine which lymph nodes are the first to drain the tumor and therefore at highest risk for disease spread. So instead of removing all of the lymph nodes that drain the tumor, this technique tells surgeons specifically which lymph nodes should be removed.
When it was first introduced, sentinel lymph node biopsy signified a breakthrough in cancer mapping. It makes for a less invasive surgery for patients with a smaller risk of potentially life-altering side effects such as lymphedema. But like all medical advancements, it’s not perfect. The blue dye frequently used is harder to see and consequently, less effective in patients with a higher body mass index (BMI). This is particularly a problem considering the association between cancer and obesity.
The relationship between cancer and obesity is well established. Research shows that excess body fat increases your risk for several types of cancer. This includes uterine cancer (also called endometrial cancer). Women who are obese (those with a body mass index of 30 or higher) are two to four times more likely to develop uterine cancer. Even women who are slightly overweight are at an increased risk. It’s estimated that obesity is the cause of up to 40 percent of uterine cancer cases.
“So you can see why it’s problematic that the blue dyes used in sentinel node biopsy for uterine cancer becomes less effective the higher a patient’s BMI,” Frumovitz says.
But a new green dye is making it easier to map the lymphatic system. In a phase 3 noninferiority trial, researchers found that a green dye used with special optical equipment that fluoresces the dye identified more lymph nodes than a blue dye in women with cervical and uterine cancers. Of course, it’s not the color that makes the two dyes different. The traditional blue dye — called isosulfan blue — can only be seen with the naked eye. The green dye — indocyanine green — is a cyanine dye that shines brightly through layers of tissue when used with near-infrared fluorescence imaging .
The green dye is approved by the Food and Drug Administration (FDA) and is commercially available for determining heart, liver and eye function. Based on the study’s results, the maker of the indocyanine green dye has applied for FDA approval to use it in lymphatic mapping.
“This could become the new standard of care for lymphatic mapping and sentinel lymph node biopsy in women with cervical and uterine cancers, and potentially, across subspecialties in surgical oncology,” Frumotvitz says.