Breast Cancer Cells in Sentinel Lymph Node Don’t Affect Survival

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A large study found that women diagnosed with early-stage breast cancer with occult metastases in the sentinel lymph node had the same survival rates as women diagnosed with early-stage breast cancer without occult metastases in the sentinel lymph node.

Occult metastases in bone marrow, which is rare, seem to be linked to worse survival, but the researchers couldn't say for sure that occult metastases in bone marrow affected survival. The research was published in the July 2011 issue of the Journal of the American Medical Association.

The sentinel lymph node (SLN) is the underarm (axillary) lymph node closest to a breast cancer. During surgery to remove early-stage breast cancer, the sentinel node often is removed and sent to a pathologist who determines if there is cancer in it. Removing just the sentinel node is called sentinel node biopsy or sentinel node dissection.

Sentinel node dissection may be done even if the sentinel node looks normal and shows no signs of cancer on an ultrasound or x-ray. Doctors call this "clinically negative." Still, a pathologist may find single cancer cells or small groups of cancer cells in a sentinel node that is clinically negative. These single and small groups of cancer cells are called occult metastases or micrometastases. Occult means the metastases are hidden or not easily seen. Some doctors also look for occult breast cancer metastases in bone marrow by doing a bone marrow biopsy.

Before this study, it wasn't clear how important occult metastases in the sentinel lymph node and/or bone marrow are. Even so, many doctors believed that women diagnosed with early-stage breast cancer with occult metastases in the sentinel node and/or bone marrow have a worse prognosis than women without metastases in either place. A doctor who believes this may recommend a more aggressive treatment plan if occult metastases are found.

In this study, called the Z0010 trial, researchers looked at the medical records of 5,210 women diagnosed between 1999 and 2003 with early-stage breast cancer with clinically negative lymph nodes. The study was done by doctors who are members of the American College of Surgeons Oncology Group. Of the 5,210 women, 5,119 had sentinel lymph node evaluation as part of their diagnosis.

Occult metastases in the sentinel lymph node were identified using two techniques in the study:

  • The standard technique involves staining (H&E staining) the biopsy tissue so the pathologist can see the physical characteristics of cancer cells under a microscope.
  • If the standard technique failed to find cancer cells, a more precise technique -- immunohistochemistry (IHC) -- was used. IHC "tags" breast cancer cells using special antibodies that attach to proteins only found in breast cancer cells. The "tagged" cancer cells can be seen under a microscope.

The researchers found that 1,215 women (23%) had occult metastases in the sentinel lymph node that were identified by standard H&E staining. Most of these women then had a bone marrow biopsy to look for occult metastases there.

Another 349 women (7%) had sentinel lymph nodes in which standard H&E staining didn't find occult metastases but IHC did. Most of these women also then had a bone marrow biopsy to look for occult metastases there.

All the women in the study were followed for an average of more than 6 years after the breast cancer diagnosis. The researchers compared the outcomes of the women with occult metastases in the lymph nodes and/or bone marrow to women who didn't have occult metastases in either place.

Some key results:

The presence of occult metastases in the sentinel lymph node didn't affect survival:

  • 95.1% of women with occult metastases in the sentinel lymph node that were found by IHC were alive 5 years after diagnosis.
  • 95.7% of women with no occult metastases in the sentinel lymph node according to IHC were alive 5 years after diagnosis.

The presence of occult metastases in the sentinel lymph node didn't affect survival without the breast cancer coming back (disease-free survival):

  • 90.4% of women with occult metastases in the sentinel lymph node that were found by IHC were alive without the cancer coming back 5 years after diagnosis.
  • 92.2% of women with no occult metastases in the sentinel lymph node according to IHC were alive without the cancer coming back 5 years after diagnosis.

Of the women who had bone marrow biopsy, 9.9% with occult metastases in the bone marrow had died from breast cancer 5 years after diagnosis compared to 5% of women who didn't have occult metastases in bone marrow.

Still, the number of women who had bone marrow biopsy and died was small and it wasn't clear if the occult breast cancer metastases in the bone marrow were linked to worse survival. The researchers didn't recommend that bone marrow biopsy routinely be done in women diagnosed with early-stage breast cancer.

These results agree with results from another large study called NSABP B-32. NSABP B-32 found that women diagnosed with early-stage breast cancer with occult metastases in a clinically negative sentinel lymph node do almost as well as women without occult metastases.

Some doctors believe that occult metastases in a clinically negative sentinel node mean a woman needs a more aggressive treatment plan to reduce the risk of the cancer coming back (recurrence) and improve prognosis. A more aggressive treatment plan might include:

  • removing other underarm lymph nodes (axillary node dissection)
  • radiation therapy to the underarm lymph nodes (axillary irradiation)
  • chemotherapy after surgery
  • hormonal therapy after surgery if the cancer is hormone-receptor-positive

If you've been diagnosed with early-stage breast cancer and had sentinel lymph node biopsy, it's a good idea to talk to your doctor about the results. If any occult metastases were found, you might want ask your doctor about this study and ask if the results apply to your situation. Your doctor may recommend or may have already done axillary lymph node dissection. Or your doctor may recommend axillary lymph node radiation. If occult metastases were found and your doctor didn't recommend or do any additional treatment, you may want to ask why that decision was made. Together, you and your doctor can develop a treatment plan that makes the most sense for your unique situation.

Visit the Breastcancer.org Lymph Node Removal pages to learn more about sentinel node biopsy.

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