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Adding Local Anesthetic to Tracer Liquid Injection Reduces Pain During Sentinel Lymph Node Surgery

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Sentinel lymph node biopsy often is performed before or during breast cancer surgery to help figure out if the cancer has spread to nearby lymph nodes. The first step in sentinel lymph node biopsy is injecting a dye or radioactive tracer liquid (or both) into the nipple area. If you're awake during the procedure, this injection can be painful.

A study found that adding the local anesthetic lidocaine (a numbing medicine) to the tracer liquid can reduce pain during and after the injection. The lidocaine causes few side effects and doesn't interfere with the procedure's success.

In this study, 140 women who were going to have sentinel node biopsy got either a lidocaine cream (a topical anesthetic) applied to the skin to reduce pain or a placebo cream (a "dummy" cream). Then the women were split into three groups:

  • the first group got lidocaine mixed in with the tracer injection
  • the second group got sodium bicarbonate mixed in with the tracer injection (to raise the pH level of the injection to see if this reduced pain)
  • the third group got lidocaine and sodium bicarbonate mixed in with the tracer injection

The women who got lidocaine mixed in with the tracer injection had much less pain than women who didn't get lidocaine mixed in the injection. The lidocaine cream topical anesthetic reduced the pain a little, but not as much as having lidocaine mixed in the injection.

The sentinel lymph node is the lymph node that would first catch any fluid and cancer cells coming from the breast area. The idea behind sentinel node biopsy is if the sentinel node is identified, removed, and evaluated as free of cancer, then all other lymph nodes also are likely to be free of cancer. This means more lymph node surgery usually can be avoided.

The first step in sentinel node biopsy is to figure out which node is the sentinel node. A common way to do this is to inject a radioactive tracer liquid into the breast tissue. A special instrument then tracks the path of the radioactive liquid as it moves through the breast tissue to see which lymph node it travels to first. That node is the sentinel node. The surgeon then removes the sentinel node (and sometimes other lymph nodes that are very close to it) and sends it out for evaluation. The sentinel node is examined in the lab by a pathologist to see if cancer cells are in the node. If cancer cells are present, surgery to remove other lymph nodes in the area usually is done later (called axillary lymph node dissection). But if the sentinel node is "clean" then more lymph node surgery usually isn't done.

If your doctor is planning to do a sentinel node biopsy as part of your evaluation before surgery, you might want to ask if you can have an anesthetic medicine such as lidocaine mixed in with your injection. Anything you and your doctor can do to make your experience more comfortable is part of taking the best care of you and is worth asking for.

You can learn more about sentinel node biopsy in the Lymph Node Removal section.

Editor's note: To make sure that women have the appropriate lymph node surgery, the American Society for Clinical Oncology released guidelines on sentinel lymph node biopsy for people diagnosed with early-stage breast cancer. The guidelines say sentinel lymph node biopsy SHOULD be offered under these circumstances:

  • breast cancer in which there is more than one tumor, all of which have formed separately from one another (doctors call these multicentric tumors); these types of breast cancers are rare
  • DCIS treated with mastectomy
  • women who have previously had breast cancer surgery or axillary lymph node surgery
  • women who have been treated before with chemotherapy or another systemic treatment (treatment before surgery is called neoadjuvant treatment)

Sentinel node biopsy SHOULD NOT be offered under these circumstances:

  • the cancer is 5 cm or larger or locally advanced (the cancer has spread extensively in the breast or to the nearby lymph nodes)
  • the cancer is inflammatory breast cancer
  • DCIS treated with lumpectomy
  • the woman is pregnant

The guidelines also say:

  • Women with negative sentinel node biopsies shouldn’t have axillary node surgery.
  • Women with one or two positive sentinel nodes who plan to have lumpectomy plus radiation also don’t need axillary node surgery.
  • Women who have one or more positive sentinel nodes and plan to have mastectomy with no radiation should be offered axillary node surgery.

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