Subtype-Guided ¹⁸F-FDG PET/CT in Tailoring Axillary Surgery Among Patients with Node-Positive Breast Cancer Treated with Neoadjuvant Chemotherapy: A Feasibility Study

Background: The purpose of this study was to investigate the value of ¹⁸[F]-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) in tailoring axillary surgery by predicting nodal response among patients with node-positive breast cancer after neoadjuvant chemotherapy (NAC). Methods: One hundred thirty-three patients with breast cancer with biopsy-confirmed nodal metastasis were prospectively enrolled. ¹⁸F-FDG PET/CT scan was performed before NAC (a second one after two cycles with baseline maximum standardized uptake value [SUV_max] ≥2.5), and a subset of patients underwent targeted axillary dissection (TAD). All the patients underwent axillary lymph node dissection (ALND). The accuracy was calculated by a comparison with the final pathologic results. Results: With the cutoff value of 2.5 for baseline SUV_max and 78.4% for change in SUV_max, sequential ¹⁸F-FDG PET/CT scans demonstrated a sensitivity of 79.0% and specificity of 71.4% in predicting axillary pathologic complete response with an area under curve (AUC) of 0.75 (95% confidence interval, 0.65–0.84). Explorative subgroup analyses indicated little value for estrogen receptor (ER)-negative, human epidermal growth factor receptor 2 (HER2)-positive patients (AUC, 0.55; sensitivity, 56.5%; specificity, 50.0%). Application of ¹⁸F-FDG PET/CT could spare 19 patients from supplementary ALNDs and reduce one of three false-negative cases in TAD among the remaining patients without ER-negative/HER2-positive subtype. Conclusion: Application of the subtype-guided ¹⁸F-FDG PET/CT could accurately predict nodal response and aid in tailoring axillary surgery among patients with node-positive breast cancer after NAC, which includes identifying candidates appropriate for TAD or directly proceeding to ALND. This approach might help to avoid false-negative events in TAD. Implications for Practice: This feasibility study showed that ¹⁸[F]-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) could accurately predict nodal response after neoadjuvant chemotherapy (NAC) among patients with breast cancer with initial nodal metastasis except in estrogen receptor-negative, human epidermal growth factor receptor 2-positive subtype. Furthermore, the incorporation of ¹⁸F-FDG PET/CT can tailor subsequent axillary surgery by identifying patients with residual nodal disease, thus sparing those patients supplementary axillary lymph node dissection. Finally, we have proposed a possibly feasible flowchart involving ¹⁸F-FDG PET/CT that might be applied in post-NAC axillary evaluation.