18F-fluorodeoxyglucose (FDG) PET is increasingly used in staging advanced or recurrent breast cancer and in monitoring response to therapy and has received approval for Medicare re-imbursement for these clinical indications. C
There are few reports in the literature comparing PET with conventional imaging methods for breast cancer staging or restaging. In one report, the accuracy of PET was compared with CT and MRI in 75 patients with suspected recurrent or metastatic disease. PET performed well in this small series, detecting 28 of 29 patients with lymph node disease, 15 of 15 patients with bone metastases, 5 of 6 patients with lung metastases, and 2 of 2 patients with liver metastases. PET detected 8 lymph node metastases and 7 bone metastases that were not detected by CT or MRI. Hubner et al14 found PET to have an 85% sensitivity and 73% specificity versus 71% and 54%, respectively, for CT. In another series of 57 patients, all referred because of a suspicion of disease recurrence, sensitivity and specificity of PET on a per patient basis were 93% and 79%, respectively.On a per lesion basis, the sensitivity and specificity values were 85% and 79%, respectively. A disproportionate number of false-negative exams involved osseous metastases. When only non-osseous metastases were included in the lesion analysis, the sensitivity rose to 96%. Lower sensitivity for detection of bone metastases has been noted in other series. Cook et al found that bone scintigraphy is more accurate than PET for osteoblastic bone metastases, while PET is more accurate for osteolytic metastases. It is also well established that PET is not sufficiently sensitive for detecting brain metastases. This is attributed to the high background FDG activity in cerebral gray matter, obscuring small metastases. Nevertheless, PET has generally repalced CT scans for staging and restaging, although it will likely not replace MRI of the brain and whole body bone scintigraphy for evaluating brain and bones9see MS-48).
NCCN does not specifically address PET for restaging. It discourages its use in lieu of a biopsy to document recurrent disease((MS-36). NCCN accepts PET for initial staging of patients with locally advanced or metastatic breast cancer when conventional staging studies (e.g., CT or bone scan) are equivocal or suspicious or for follow-up or surveillance patients with breast cancer when conventional studies (e.g., CT or bone scan) are equivocal or suspicious. It recommends it primarily for when other studies are equivocal but also reports that the consensus of the panel is that it can be used optionally(Category2B) for restaging(MS-37). A recent review (Rosen et al) says: “FDG PET and PET/CT have been shown to be particularly useful in the restaging of breast cancer, in evaluation of response to therapy, and as a problem-solving method when results of conventional imaging are equivocal. In these situations, FDG PET often demonstrates locoregional or unsuspected distant disease that affects management. PET has demonstrated a particular capability for evaluation of chemotherapy response in both patients with locally advanced breast carcinoma and those with metastatic disease.” NICE says: “Positron emission tomography fused with computed tomography (PET-CT) should only be used to make a new diagnosis of metastases for patients with breast cancer whose imaging is suspicious but not diagnostic of metastatic disease.
Eric L. Rosen FDG PET, PET/CT, and Breast Cancer Imaging 1 October 2007 RadioGraphics, 27, S215-S229.
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Griffeth LK, Rich KM, Dehdashti F, et al. Brain metastases from non-central nervous system tumors: Evaluation with PET. Radiology. 1993;186:13-15.