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 ((18)F-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. (18)F-FDG PET/CT scan was performed before NAC (a second one after two cycles with baseline maximum standardized uptake value [SUVmax] >/=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 SUVmax and 78.4% for change in SUVmax, sequential (18)F-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 (18)F-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 (18)F-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 ((18)F-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 (18)F-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 (18)F-FDG PET/CT that might be applied in post-NAC axillary evaluation.