The staging of invasive lobular breast cancer is better left to CT and bone scans, rather than FDG-PET/CT, according to a study presented at the American Roentgen Ray Society (ARRS) meeting in Toronto.
Researchers at Memorial Sloan Kettering Cancer Center found that only 3% of patients with newly diagnosed stage III invasive lobular breast cancer would have benefited from systemic staging with FDG-PET/CT, versus conventional CT and bone scanning.
The findings run counter to guidelines from the National Comprehensive Cancer Network (NCCN), which considers FDG-PET/CT appropriate for systemic staging of newly diagnosed stage III breast cancer. However, tumor histology may affect the usefulness of FDG-PET/CT for staging these patients, according to Dr. Molly Parsons, co-author of the current study.
FDG-PET/CT did not find unsuspected local extra-axillary nodes in any of the 146 patients in the study. The modality did not identify unsuspected distant metastases in any of the eight patients with initial stage I cancer, while it found distant metastases in two (4%) of 50 patients with initial stage II disease and 10 (11%) of 88 with initial stage III invasive lobular breast cancer.
Twelve patients were upstaged to stage IV by FDG-PET/CT, which was confirmed by pathology. Of those 12 patients, nine would have been upstaged by CT, bone scans, or both. The remaining three cases had osseous metastases without a bone scan for comparison. Two false-positive FDG-PET findings led to unnecessary additional tests and a biopsy of a benign adrenal adenoma, the researchers noted.
At best, staging with FDG-PET/CT would have benefited three (3%) of 88 patients with newly diagnosed stage III invasive lobular breast cancer, compared with conventional CT and bone scanning. Although FDG-PET/CT is valuable for systemic staging of stage III ductal breast cancer, it does not appear to be useful for staging invasive lobular breast cancer, the group concluded.
