A prospective study evaluating 18F-Fluorodeoxyglucose (18FDG) positron emission tomography (PET) in the assessment of axillary nodal spread in women undergoing sentinel lymph node biopsy (SLNB) for breast cancer

Abstract

533 Background: In women with operable breast cancer, SLNB is often used to assess the axilla. 18FDG PET imaging is potentially useful because of preferential uptake of 18FDG by metabolically active tumor cells. Prior studies of PET in breast cancer have not included many women undergoing SLNB. Methods: Women with operable breast cancer diagnosed within the previous 3 months underwent 18FDG PET followed by SLNB. Axillary node assessment (ANA) consisted of SLNB alone if negative, SLNB with axillary lymph node dissection (ALND) if the SLNB or preoperative PET scan was positive or ALND alone if sentinel nodes were not identified. We considered that PET would be useful if the specificity was 95% or better. Based on a 30% prevalence of women with positive axillary nodes, 320 women were needed so that the lower boundary of the 95% CI for specificity would exclude 91%. Patients were scanned at one of 5 study centers in Ontario, using either a PET scanner or PET/CT instrumentation. Results: Between January 2005 and March 2007, 336 women were entered; 11 were not analyzable. Sentinel nodes were found for 312/325 women (96%) and were positive for tumor by H&E stain in 92 (30%). ALND was performed in 177 (54%) and was positive for tumor in 43 cases (25%): Using logistic regression, age, BMI, number of nodes, and tumor size were assessed as predictors of prevalence, positive PET, and sensitivity. Only tumor size was predictive (p<0.05) for prevalence (OR=1.6), PET positivity (OR=1.7) and PET sensitivity (OR=1.4). Conclusions: 18FDG PET is not sufficiently sensitive to detect positive axillary lymph nodes. However, the very high positive predictive value (96%) in our trial suggests that PET could be used in women with large primary tumors to identify those in whom SLNB may be avoided prior to therapeutic ALND. Parameter Estimate 95% CI Sensitivity 23.0% 15.2% - 32.5% Specificity 99.6% 97.6% - 99.9% Positive Predictive Value 95.8% 78.9% - 99.9% Negative Predictive Value 74.4% 69.1% - 79.3% Prevalence 30.8% 25.8% - 36.1% Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Aventis, Biomera, Ortho Biotech, Pfizer, Pharmacia, Roche, YM Biosciences AstraZeneca, Aventis, Pfizer, Pharmacia AstraZeneca, Aventis