LOS ANGELES -- For some breast cancer patients, a PET scan imaging strategy may allow surgeons to bypass sentinel lymph node or needle biopsies.
LOS ANGELES, Aug 21 -- For staging some breast tumors, a PET scan imaging strategy may allow surgeons to bypass sentinel lymph node or needle biopsies.
That conclusion emerged from a case series of 51 women with 54 invasive breast tumors, reported Alice Chung, M.D., of Cedars-Sinai Medical Center here, and colleagues, in the August Archives of Surgery.
A high level of fludeoxyglucose F 18 (FDG) PET in the axilla-defined as a standardized uptake value of more than 2.3-- confirmed the presence of axillary nodal metastases with 60% sensitivity and 100% specificity and a positive predictive value of 100%, they wrote.
If this standardized uptake value threshold is "validated and can predict node positivity with 100% specificity, chemotherapy can be initiated or a surgeon can proceed directly to [axillary node dissection] for locoregional control."
The mean age of patients was 54, the mean tumor size was 3.0 cm, and the mean modified Bloom-Richardson score was 7.6 (range 3.0-9.0).
Thirty-two of the women had axillary activity identified on FDG-PET. There were 60 "hot" axillary sites with standardized uptake values ranging form 0.7 to 11.0, they wrote.
Twenty patients had standardized uptake values of 2.3 or greater. In a logistic regression model, standardized uptake values were a significant predictor of node positivity (P=0.01) and axillary nodes with an standardized uptake value of 2.3 or greater were 15 times more likely to contain metastasis than nodes with standardized uptake values of less than 2.3, they wrote.
The standardized uptake value quantifies regional tracer uptake, normalized to the administered dose of tracer, which the authors contended was a more objective measure than the visual analysis of PET scans that has been used in other studies.
For example, in this series four patients with axillary activity but standardized uptake values of less than 2.3 were later indicated negative lymph nodes. If the authors had relied on visual analysis alone, these four patients would have been false positives.
The Cedars-Sinai group noted that the study was limited by its retrospective design. Moreover, when compared with an average cohort of patients with breast cancer, their patients had slightly larger primary tumors (3 cm), a high rate of positive axillary lymph nodes (67%), a high rate of clinically palpable axillary lymph nodes (35%) ,and a low rate of [sentinel node biopsy] (46%), demonstrating a selection bias.
The authors also cautioned that standardized uptake values should be an "adjuvant to clinical judgment" especially because they will vary among PET centers by 10% to 15%, "even with the same acquisition protocol, owing to technical and calibration factors."