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New Study Suggests Number of Lymph Nodes May Be Linked to Breast Cancer Survival (dateline January 6, 2000)

Researchers at the Yale University School of Medicine have discovered that the total number of lymph nodes present may be related to a woman’s risk of dying from breast cancer when there is no evidence that cancer has spread past the breast. The study indicated that women with less than 20 axillary (underarm) lymph nodes have a greater chance of surviving breast cancer than women with more than 20 nodes. If confirmed by other studies, the Yale study may help physicians improve their method for determining a patient’s breast cancer survival rate.

The researchers studied 290 women who had previously underwent breast surgery ( lumpectomy or mastectomy) but whose cancer had not spread past the breast to the lymph nodes. The results of the studied indicated that the five-year survival rate for women with fewer than 20 tumor-free lymph nodes was 84.7% compared with 96.3% for patients with 20 or more tumor-free lymph nodes. The researchers also found that women with a total count of 20 or more axillary (underarm) lymph nodes were 4.33 times more likely to die in the first five years after surgery from the spread of breast cancer than women with fewer than 20 axillary lymph nodes.

Presently, physicians determine breast cancer survival after breast surgery by counting the number of malignant (cancerous) underarm lymph nodes. This method indicates how severe the breast cancer has metastasized (spread). However, approximately 10% to 15% of women die from the spread of breast cancer even though all of their axillary lymph nodes are cancer-free.

Lymph nodes are key components of the lymphatic system—an essential element of the body’s immune system. Lymph nodes help remove cell waste and fight infections. Robert Camp, PhD, of Yale University School of Medicine, said that there is generally little variation in the total number of lymph nodes from woman to woman. The average woman has 10 to 14 axillary (underarm) lymph nodes. However, more aggressive tumors may cause the nodes to swell, giving the appearance that more nodes exist. Camp believes the Yale study will prompt other researchers to investigate how to stop breast tumors from spreading past the breast to the underarm lymph nodes and other areas of the body (such as the bone, lung, liver, or brain).

Though counting the number of lymph nodes is a promising new technique to help physicians learn more about breast cancer survival, lymph nodes are often very difficult to detect. The Yale study involved counting lymph nodes during breast surgery. Though some nodes may be seen by mammogram, ultrasound, CT scan or MRI scan , it is difficult to determine the exact number of nodes present with any test or procedure, even surgery. (Note: mammogram, ultrasound, CT scan, and MRI scan are not currently used to detect lymph nodes).

Many women who undergo mastectomy (removal of the affected breast) for breast cancer have some or all of their axillary lymph nodes removed to help stage their cancers and determine their chances of survival. Recently, a new diagnostic procedure called sentinel node biopsy has been developed that helps eliminate the need to remove many of the underarm lymph nodes. Sentinel node biopsy involves the removal of only one lymph node (the sentinel node) to determine breast cancer spread. If the sentinel node biopsy procedure becomes more widely utilized, surgeons may not ever know the total number of cancer-free lymph nodes in many of their patients.