The Role of 18F-FDG PET/CT in Predicting the Neoadjuvant Treatment Response in Patients with Locally Advanced Breast Cancer.

Purpose: Patients with locally advanced breast cancer (LABC) should be treated with neoadjuvant chemotherapy (NAC). Pathological complete response (pCR) is related to better disease-free survival (DFS). The best strategy for assessing the efficacy of NAC has not been established yet, but several studies have shown that 18F-FDG PET/CT is a potential imaging tool for assessing pCR. The aim of this study is to investigate the merits of 18F-FDG PET/CT imaging in predicting pCR in both axillary and breast tissue and to establish a threshold maximum standard uptake value (SUVmax) for predicting the response after completion of NAC. Methods: A total of 186 LABC patients, treated with an NAC regimen according to tumor subtype, were retrospectively analyzed in this study. All patients underwent 18F-FDG PET/CT imaging before and after completion of NAC. PET parameters were measured in the most FDG avid breast tissue and axillary lymph nodes. We analyzed the correlation between the tumor SUVmax of the PET/CT response and the pCR after surgery. DFS was also evaluated with respect to pCR. Results: Higher pCR rates were significantly associated with a higher tumor grade, an initial Ki-67 ≥20% (p = 0.03 and p = 0.003, respectively), a triple-negative subtype (32.9%), and a human epidermal growth factor receptor 2 (HER-2)-positive subtype (24.7%) (p < 0.001). There was a significant correlation between the pCR and a complete response in 18F-FDG PET/CT (p < 0.001). The overall sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 18F-FDG PET/CT to determine the pCR after NAC were 100%, 72.2%, 85%, 75.2%, and 100%, respectively. We demonstrated a 1.1 cutoff SUVmax for breast tumors after NAC (OR: 3.94, 95% CI: 1.14–5.05, p = 0.004), the 18F-FDG PET/CT response to NAC (OR: 0.50, 95% CI: 0.25–0.99, p = 0.003), and the molecular subtype of breast tumors (OR: 0.58, 95% CI: 0.38–0.88, p = 0.011). Conclusion: Our results confirm that 18F-FDG PET/CT is a useful method for predicting the NAC response in LABC.