A Prospective Evaluation of Positron Emission Tomography Scanning, Sentinel Lymph Node Biopsy, and Standard Axillary Dissection for Axillary Staging in Patients with Early Stage Breast Cancer
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BACKGROUND: Positron emission tomography (PET) is a noninvasive imaging modality that can detect malignant lymph nodes. This study determined the sensitivity, specificity, predictive values, and likelihood ratios of PET scanning compared with standard axillary lymph node dissection (ALND) and sentinel lymph node biopsy (SLNB) in staging the axilla in women with early stage breast cancer. METHODS: Women with clinical stage I or II breast cancer had whole body PET scanning before ALND and SLNB, in a prospective, blinded protocol. ALND were evaluated by standard hematoxylin and eosin (H&E) staining techniques, while sentinel nodes were also examined for micrometastatic disease. RESULTS: A total of 98 patients were recruited. PET compared with ALND demonstrated sensitivity of 0.40 (95% CI, 0.16, 0.68), specificity 0.97 (CI, 0.90, 0.99), positive likelihood ratio 14.4 (CI, 3.21, 64.5), positive predictive value 0.75 (CI, 0.35, 0.97), and false-negative rate of 0.60 (CI, 0.32, 0.84). Test properties were similar for PET compared with sentinel nodes positive by H&E staining. A few false-positive scans (0.028, CI, 0.003, 0.097) were seen. Multiple logistic regression analysis found that PET accuracy was better in patients with high grade and larger tumors. Increased size and number of positive nodes were also associated with a positive PET scan. CONCLUSIONS: The sensitivity of PET compared with ALND and SLNB was low, whereas PET scanning had high specificity and positive predictive values. The study suggests that PET scanning cannot replace histologic staging in early stage breast cancer. The low rate of false-positive findings suggests that PET can identify women who can forego SLNB and require full axillary dissection.
