When surgeons take out a tumor, they often remove nearby lymph nodes to be examined for cancer cells that may have spread. This longstanding practice is important for guiding treatment decisions, but it requires more extensive surgery and increases risk of complications.
Beginning in 2003, Memorial Sloan Kettering gynecologic surgeons, led by Nadeem Abu-Rustum, pioneered the use of a technique called sentinel lymph node mapping (SLNM) to stage gynecologic cancers. SLNM is a way to detect whether cells have escaped a tumor and spread to the sentinel nodes — the first lymph nodes to which the cancer is likely to spread. This method had already been well-established to treat breast cancers.
Although MSK’s surgeons have since incorporated SLNM into routine practice for gynecologic cancers — first with cervical, then endometrial cancer — many physicians at other institutions have been reluctant to adopt the approach, mainly due to fears they would overlook nodes containing metastatic cancer cells.
Now a new study has validated the MSK method of using SLNM for staging endometrial cancer. It shows that the MSK technique works as well as traditional lymph node removal for detecting cancer spread and that there is no difference in how long patients survive.
“This finding could truly change how endometrial cancer is treated, improving patients’ quality of life without placing them at risk for undetected cancer,” says MSK gynecologic surgeon Mario Leitao, who led the study.
Problems With the Conventional Method
Traditionally, surgeons treating women with early-stage gynecologic cancers removed numerous lymph nodes in the pelvis — sometimes as many as 50. This practice, called pelvic and para-aortic lymphadenectomy, was developed more than 20 years ago and has since been widely adopted.
However, this invasive approach can have serious side effects. One of the most common is lymphedema of the legs, an often debilitating condition characterized by painful swelling and skin changes that leave the patient vulnerable to infection.
Lymphedema seriously impairs day-to-day quality of life, and it can persist for decades. The long-term effects are especially disheartening for women with early-stage forms of endometrial cancer. These patients are cured more than 90 percent of the time, and many of them are still in their 30s and 40s.Back to top
Removing Only the Nodes that Matter
The SLNM method developed and refined by Dr. Abu-Rustum is strikingly low-tech, relying on the skill of the surgeon rather than highly advanced imaging methods. Just before the operation to remove the tumor, the surgeon injects dye at two precise locations in the patient’s cervix. (MSK surgeons initially used blue dye for the technique but have since switched over to a fluorescent dye called indocyanine green, which is very easy to detect under near infrared imaging.) Lymph fluid carries the dye to the sentinel node, making them easily identified.
At the same time that the tumor is taken out, the sentinel nodes are removed and examined for cancer cells by a pathologist. If they are free of cancer, usually no additional lymph nodes need to be removed. If any nodes do contain cancer cells, the surgeon may or may not remove more nodes for further inspection, and the patient may require chemotherapy or radiation following surgery.
Dr. Leitao explains that using SLNM rather than performing lymphadenectomy shortens the operation by an hour or two and also makes it possible to use minimally invasive procedures such as laparoscopy or robotic surgery.Back to top
Success of an Algorithm
To ensure cancer spread is not missed, Dr. Abu-Rustum developed an algorithm — a specific set of steps to follow — for SLNM use with stage I endometrial cancers. An essential part of this algorithm calls for the removal of additional lymph nodes when SLNM provides inconclusive results.
One key to the effectiveness of the MSK technique is that removal of fewer nodes means they can be subjected to more-exhaustive examination by pathologists. This close scrutiny, called ultrastaging, enables clinicians to be more accurate in the way they stage and define the disease.
“In fact, the SLNM approach had been deemed successful enough that in 2014, for the first time, our algorithm was included in the 2014 National Comprehensive Cancer Network guidelines as an acceptable option for treating endometrial cancer,” Dr. Leitao said. “But when any new technique is introduced, oncologists are going to be cautious — they want very solid evidence.”Back to top
A Large, Rigorous Study
The recent study, published in Gynecologic Oncology, came from a three-year collaboration between MSK and the Mayo Clinic. It compared MSK’s SLNM staging algorithm with the lymphadenectomy approach used by Mayo in 1,135 patients who were treated for early-stage endometrial cancer.
Results showed that there was no difference in patient survival rates when comparing the two techniques. The SLNM method detected cancer spread as well as lymphadenectomy — in fact, SLNM identified metastatic cells at a slightly higher rate due to the closer examination of the nodes removed.
Dr. Leitao says the results should draw a lot of attention because the evidence is so convincing.
“These findings could really impact the field because it’s the largest study of its kind involving two institutions that really set the standards for staging endometrial cancer,” he says. “This is going to bring sentinel lymph node mapping to the forefront as a valid option for many patients. It is a huge benefit if more women can be spared unnecessary node removal and the resulting side effects.”Back to top