PET Scans Predict Breast Cancer Spread

TUESDAY, Aug. 22 (HealthDay News) -- Positron emission tomography (PET) scans can help doctors ascertain whether breast cancer has spread to the axillary lymph nodes in the armpit area, California researchers have determined.

A study out of Cedars-Sinai Medical Center in Los Angeles included 51 women with invasive breast cancer, whose average age was 54.

Before the women had surgery or chemotherapy for their cancer, they all had PET scans after they'd been injected with a material similar to glucose (fludeoxyglucose F 18, or FDG), along with a chemical tracer.

Cancer cells use more FDG than normal cells. The researchers analyzed the PET scans to determine each patient's standardized uptake value -- how much of the FDG was absorbed compared to how much of it was injected.

The PET scans indicated activity in the axillary area in 32 (59 percent) of the breast cancers. Standard uptake value ranged from 0.7 to 11. The study found that 20 tumors had a value of 2.3 or greater.

The researchers set the standard uptake value at 2.3. Cancers with a higher value were considered to have spread to the lymph nodes.

Using the 2.3 threshold, the study found that the PET scans were 72 percent accurate, and had a sensitivity of 60 percent, meaning that they were able to detect 60 percent of axillary metastases.

The scans had a specificity of 100 percent (no one without metastases was identified as having metastases), and a positive predictive value (proportion of patients with a positive result who are accurately diagnosed) of 100 percent.

The study was published in the August issue of the journal Archives of Surgery.