FDG PET/CT Not Useful in Newly Diagnosed Stage III ILC Breast Cancer

Using 18F-FDG PET/CT (FDG PET/CT) for systemic staging of patients with newly diagnosed stage III breast cancer may not be useful, according to a study presented at the American Roentgen Ray Society (ARRS) 2015 Annual Meeting in Toronto, Canada.

Researchers from New York Presbyterian Hospital-Weill Cornell Medical Center and Memorial Sloan Kettering Cancer Center, New York, NY, performed a retrospective study of 146 women with stage I to III invasive lobular carcinoma (ILC).

"We are evaluating patient and disease factors that affect the value of FDG PET/CT for systemic staging of locally advanced breast cancer," coauthor Molly Parsons said in a release. "Our ongoing work suggests that the histology of the primary breast malignancy may be one such factor."

The researchers determined initial stages through physical examination, mammography, ultrasound, MRI, surgical findings, individually or combined. PET/CT studies were reinterpreted by a radiologist with board certification in diagnostic radiology and nuclear medicine with nine years of experience with PET/CT, who was blinded to results of other imaging modalities. Unsuspected extraaxillary nodal metastases and distant metastases were recorded. Upstaging by FDG PET/CT from initial clinical stage was documented.

The results showed that PET/CT did not reveal unsuspected local extraaxillary nodes in any patient.

Unsuspected distant metastases were detected in:

• None of eight initial stage I patients

• Two of 50 (4%) initial stage II patients

• 10 of 88 (11%) initial stage III ILC patients

All 12 patients upstaged to stage IV by PET/CT had results confirmed by pathology. Of these 12 patients, nine would have also been upstaged by CT, bone scan, or both, and the remaining three had osseous metastases without a bone scan for comparison. Two of the 12 were upstaged by the CT component of the PET/CT, rather than the FDG PET, as they had sclerotic osseous lesions that were not FDG avid. Two false-positive FDG PET findings led to unnecessary further tests and one biopsy of a benign adrenal adenoma.

“At best, only 3 percent (3 of 88) of patients with newly diagnosed stage III ILC breast cancer would have benefited from systemic staging with FDG PET/CT, as compared with conventional CT and bone scanning,” the researchers wrote in the abstract. “This benefit may be even smaller as bone scan comparison was not available in these three patients.”

The researchers suggested that future NCCN guidelines for systemic staging of breast cancer may need to be modified to consider the histologic subtype of the breast malignancy, with ILC staged with CT and bone scan rather than FDG PET/CT.