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Study Offers New Model for Assessing Extent of Positive Axillary Lymph Nodes in Women with Breast Cancer

PHILADELPHIA (November 1, 1999) -- A new study released today at the American Society for Therapeutic Radiology and Oncology (ASTRO) annual conference in San Antonio, Texas offers physicians a model for determining the accuracy of the assessment of the number of positive axillary lymph nodes found in breast cancer. Treatment often varies based on the number of positive nodes. The study was conducted at Fox Chase Cancer Center in Philadelphia, Pennsylvania.

In the study, a model is provided to determine the probability of four or more positive nodes in a patient. The presence of four or more positive axillary nodes is considered an indication for the addition of radiation treatment to the supraclavicular region in patients undergoing breast conservation therapy, and the chest wall and regional nodes in the post-mastectomy setting. The determination of probability was based on three factors; the number of nodes examined, the number of positive nodes, and the primary tumor size.

From 1979-1998, 1652 women were evaluated for the study. Each had stage I or II breast cancer and underwent an axillary dissection as part of their treatment. A minimum of 10 lymph nodes was examined in each patient. 526 women had more than twenty nodes examined, 516 had between 16 and 20 nodes examined and 610 women had 11-15 nodes examined. Of the patients identified with positive lymph nodes, 333 had between one and three positive nodes, 90 women had between 4 and 10 positive nodes, and 36 had more than ten lymph nodes positive.

Using the mathematical model, a patient with a T-I tumor and one positive node would need a minimum of eight nodes examined in order to have a less than 10 percent probability of having four or more positive nodes. Similarly, a patient with two positive nodes would need at least 15 nodes examined, and a patient with three positive nodes would need at least 20 nodes examined in order to reduce the probability of actually having four or more positive nodes to 10 percent.

"Previous studious studies have suggested that examination of six to ten axillary nodes from the standard axillary dissection accurately predicts nodal positivity vs. negativity," says Rajesh Iyer, M.D., a Fox Chase radiation oncologist and primary author of the paper. "However, there is little information regarding the number of nodes that need to be examined in order to accurately determine the extent of nodal positivity. This model is critical to the successful treatment of our patients. Underestimation of positive nodes could negatively influence treatment and, subsequently, result in treatment failure."

Fox Chase Cancer Center is one of 36 National Cancer Institute-designated comprehensive cancer centers in the nation. The Center's activities include basic and clinical research, prevention, detection and treatment of cancer and community outreach programs.

Fox Chase Cancer Center, part of the Temple University Health System, is one of the leading cancer research and treatment centers in the United States. Founded in 1904 in Philadelphia as one of the nation’s first cancer hospitals, Fox Chase was also among the first institutions to be designated a National Cancer Institute Comprehensive Cancer Center in 1974. Fox Chase researchers have won the highest awards in their fields, including two Nobel Prizes. Fox Chase physicians are also routinely recognized in national rankings, and the Center’s nursing program has received the Magnet recognition for excellence four consecutive times. Today, Fox Chase conducts a broad array of nationally competitive basic, translational, and clinical research, with special programs in cancer prevention, detection, survivorship, and community outreach.  For more information, call 1-888-FOX CHASE or (1-888-369-2427).

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