(ChemotherapyAdvisor) – When positive, 2-[18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) is indicative of disease in axillary nodes in patients with breast cancer, which may influence surgical care; however, FDG-PET is not sufficiently sensitive to detect positive axillary lymph nodes nor sufficiently specific to appropriately identify distant metastases, a study in the Journal of Clinical Oncology online March 5 has found.

“In the breast cancer setting, we aimed to determine how FDG-PET could be incorporated into the assessment of the axilla in women with early-stage breast cancer undergoing sentinel lymph node biopsy,” investigators from the Ontario Clinical Oncology Group Study stated. “Our results suggest that PET scanning could be useful in the staging of early-stage breast cancer only to identify patients with fairly high axillary lymph node burden who could then move directly to axillary lymph node dissection and would not require the additional step of sentinel lymph node biopsy. In our study, this would apply to only 10% of women studied.”

The prospective study assessed regional nodal spread of disease in 325 women who underwent FDG-PET within three months of diagnosis followed by axillary lymph node assessment consisting of sentinel lymph node biopsy alone if sentinel lymph nodes were negative; sentinel lymph node biopsy with axillary lymph node dissection if or FDG-PET was positive; or axillary lymph node dissection alone if sentinel lymph nodes were not identified.

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Sentinel nodes were found for 312 of 325 women (96%) and were positive for tumor in 90 of 312 (29%). Axillary lymph node dissection was positive in seven additional women. Using axillary lymph node assessment as the gold standard, sensitivity for PET was 23.7%; specificity was 99.6%; positive predictive value was 95.8%; negative predictive value was 75.4%; and prevalence was 29.8%.

Tumor size was found to be predictive for prevalence of tumor in the axilla and for FDG-PET sensitivity. FDG-PET scan was suspicious for distant metastases in 13 patients; three (0.9%) were confirmed as metastatic disease and ten (3.0%) were false positive.

The investigators concluded that “routine use of FDG-PET is not indicated in these women, and sentinel lymph node biopsy remains the preferred technique for axillary staging in women with stage I and II breast cancer.”