The role of interim ¹⁸F-FDG PET/CT in predicting early response to neoadjuvant chemotherapy in breast cancer

Aim: The aim of this study was to prove the diagnostic value of interim ¹⁸F-Fluorodeoxyglucose-positron-emission tomography combined with computed tomography (PET/CT) scan for predicting pathological complete response (pCR) compared to other factors in neoadjuvant chemotheraphy. Patients and Methods: Twenty-seven patients with breast cancer were included in this retrospective study. They all underwent scheduled neoadjuvant chemotherapy. Patients underwent PET/CT at baseline, mid-point (interim), and preoperatively (after completion of chemotherapy). The metabolic response was calculated as follows: ΔStandardized uptake value (SUV)(%)=(1st SUV_max-2nd SUV_max)/1st SUV_maxx100. Results: The change in SUV_max between baseline and interim PET/CT scans was significantly larger than between interim and preoperative PET/CT scan. An optimal cut-off ΔSUV value of 78.3% was proposed for discriminating patients with pCR from those without pCR. Metabolic CR, defined as a change of SUV_max greater than the cut-off value, can predict pCR according to univariate analysis (p=0.012; Relative risk (RR)=25.3). Furthermore, metabolic CR was the most powerful factor for predicting pCR than other possible factors according to multivariate analysis (p=0.003). Conclusion: It is possible to use interim ¹⁸F-FDG PET-CT as an effective method to predict early response in patients with breast cancer treated with neoadjuvant chemotherapy.