Sentinel lymph node biopsy: What cancer patients should know

We often hear about lymph nodes when we talk about how cancer spreads. That’s because when cancer starts to spread, it often goes to the lymph nodes first.

When treating breast cancer and melanoma, and – increasingly -- head and neck cancers and gynecologic cancers, physicians use a diagnostic method called sentinel lymph node biopsy, which looks at a patient’s lymph nodes to determine whether the cancer has spread and what type of cancer treatment is needed. At MD Anderson, our doctors often use sentinel lymph node biopsies because, in many cases, they help better detect cancer. In fact, about 20-30% of “node-negative” patients have disease present in their lymph nodes even though CT scans and/or ultrasound studies suggest that the lymph nodes are negative or do not contain disease.

We spoke with head and neck surgeon Stephen Lai, M.D., Ph.D., to learn more.  

What is a sentinel lymph node biopsy?

Sentinel lymph nodes are an important part of the immune system, and they contain the cells that monitor foreign substances, like bacteria, viruses and cancer. Sentinel lymph node mapping helps to identify the lymph nodes that are at highest risk for containing cancer.

A sentinel lymph node biopsy (SLNB) is a surgical approach to identify and remove the sentinel lymph node to determine if the cancer has spread, and if so, how far.

In most cases, a negative sentinel lymph node biopsy means the cancer has not spread. A positive biopsy means cancer was found in the lymph node. It could be in other lymph nodes and even other organs.

What happens during a sentinel lymph node biopsy?

A surgeon injects a marker called a radiotracer around the site of the tumor. The radiotracer flows through the lymphatic system – a path or network of lymph channels and nodes. This allows the surgeon to see what lymph nodes are draining from the tumor first and identify a sentinel lymph node.

Then, the surgeon makes a small incision in the skin and identifies the lymph node for removal. A pathologist studies the lymph node to determine if it contains cancer.

What are the benefits of sentinel lymph node biopsy?

This technique uses a smaller incision and can prevent patients from needing a more invasive surgery. It can shorten postoperative recovery times and lower the risk of side effects like lymphedema, swelling caused by the removal of more lymph nodes. 

A sentinel lymph node biopsy is often performed as an outpatient procedure, and patients are typically able to leave the hospital that day, unless they’re having additional surgery.

What are the risks of a sentinel lymph node biopsy?

The risks are very low risk, aside from the very low chance -- 2 to 4% -- that a sentinel lymph node would not be able to be identified.

Some patients have concerns about the radiotracer used to find the sentinel lymph node. While it is radioactive, the tracer has a very low-energy emission particle. No severe adverse reactions have been reported, and the only negative reaction reported has been rare episodes of brief pain during the injection. 

Patients who have a sentinel lymph node biopsy may also experience lymphedema, but they’re less likely to than those who have an open surgery.

Tell me about advances in using sentinel lymph node biopsies to help more cancer patients. 

Sentinel lymph node biopsy has been very well established for melanoma and breast cancer treatment. It’s also more commonly used in Europe for early-stage oral cavity cancer, and is being increasingly used in the U.S. I completed a Phase III clinical trial that led to the Food and Drug Administration approval of a new radiotracer for use in patients with oral cavity cancer. Now, I am leading an effort to start a Phase III clinical trial comparing sentinel lymph node biopsy to a more traditional technique called an elective neck dissection for early-stage oral cavity cancer patients. In addition, Michael Frumovitz, M.D., recently completed a Phase III clinical trial using a new type of dye in sentinel lymph node detection in patients with cervical and uterine cancers. These advances help us learn more about the cancer itself, while lessening side effects for patients.

Sentinel lymph node biopsy is personalized surgery. The surgery is tailored to the individual patient to target the lymph nodes most likely to harbor cancer. It helps patients get back to their everyday lives more quickly. It’s all about detecting the cancer effective and accurately in a way that helps the patients maintain their quality of life.

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