18F-PET/CT (FDG PET/CT) is valuable for systemic staging of stage III ductal breast cancer; however, it adds little to the systemic staging of invasive lobular cancer. These findings were presented at the American Roentgen Ray Society Annual Meeting in Toronto, Ontario, Canada.

Although National Comprehensive Cancer Network (NCCN) guidelines consider FDG PET/CT appropriate for systemic staging of newly diagnosed stage III breast cancer, the technique may not be equally valuable for all breast cancer histologies, according to researchers.

“We are evaluating patient and disease factors that affect the value of FDG PET/CT for systemic staging of locally advanced breast cancer,” said study coauthor Molly Parsons, MD, of Memorial Sloan Kettering Cancer Center in New York, New York. “Our ongoing work suggests that the histology of the primary breast malignancy may be one such factor.”

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The retrospective study examined records of 146 patients. No unsuspected local extra-axillary nodes were revealed with FDG PET/CT in any patient. Of the 12 patients who were upstaged based on PET/CT, nine would have been upstaged using CT, bone scan, or both; and the remaining three had osseous metastases without a bone scan for comparison.

The researchers found that, at best, only 3% of patients with newly diagnosed stage III invasive lobular cancer would have benefited from systemic staging with FDG PET/CT, compared with conventional CT and bone scan. The results suggest that invasive lobular cancer should be staged with CT and bone scan, rather than FDG PET/CT. The researchers suggest that future NCCN guidelines for systemic staging of breast cancer need to consider the histologic subtype of the breast malignancy.