Lymph Node Ultrasound Imaging Most Effective for Obese Breast Cancer Patients

New research into whether ultrasound imaging used to identify breast cancer in underarm lymph nodes is less effective in obese women, has generated an unexpected finding. Fat did not obscure the images and ultrasound imaging showing no suspicious lymph nodes actually was shown to be more accurate in overweight and obese patients than in women with a normal body mass index.

The research was among several Mayo Clinic (Rochester, MN, USA) studies presented at the American Society of Breast Surgeons annual meeting, held April 30–May 4, 2014, in Las Vegas (NV, USA).

Researchers studied 1,331 breast cancer patients who received ultrasounds of their axillary lymph nodes, the lymph nodes in the armpits, to check for cancer before surgery. Of those patients, 36% were considered obese, with a body mass index of 30 or more. Body mass index is a formula that uses weight and height to estimate body fat. Of the other women evaluated, 33% were of normal weight and 31% were overweight but not obese.

Obesity can change lymph nodes, including the way they look in imaging studies, and make physical exam of underarm lymph nodes more challenging. The Mayo study discovered that higher body weight did not cloud ultrasound images of the axillary lymph nodes in overweight or obese cancer patients, and that their ultrasound scans had better specificity and accuracy than those of thinner women, meaning that when ultrasound showed no suspicious lymph nodes, it was likelier to be correct. “I think we were surprised at these results,” noted senior author Tina Hieken, MD, a breast cancer surgeon at Mayo Clinic. “It should be very reassuring that regardless of the weight of the patient, axillary ultrasound is helpful.”

Potential reasons for the findings, Dr. Hieken hypothesizes: Soft fatty tissue can be compressed during ultrasound scanning, and physicians now have more experience in knowing what lymph nodes may look like in overweight and obese patients. In some thin patients, ultrasounds may not yield as much information because underarm lymph nodes can be so close to the surface, it may be difficult to get good images, she reported.

Surgeons do not rely on ultrasound by itself to determine whether or not breast cancer has spread; it is one of several sources of information used to guide treatment. “For most patients with invasive breast cancer, if the axillary ultrasound is negative, we perform a sentinel lymph node biopsy at the time of the breast operation to make sure cancer has not spread. When the preoperative axillary ultrasound shows suspicious lymph nodes, we then do a fine-needle aspiration of the lymph nodes. If that shows cancer, we may discuss other strategies with the patient such as giving chemotherapy before surgery,” Dr. Hieken said.

More research is planned, including evaluating at different techniques of lymph node ultrasound to improve accuracy and perhaps to avoid axillary lymph node surgery altogether in some breast cancer patients with small tumors and negative axillary ultrasounds, Dr. Hieken reported.

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