Early assessment of response to neoadjuvant chemotherapy with ¹⁸F-FDG-PET/CT in patients with advanced-stage ovarian cancer

Purpose The aim of this study was to evaluate the ability of sequential ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) after one cycle of neoadjuvant chemotherapy (NAC) to predict chemotherapy response before interval debulking surgery (IDS) in advanced-stage ovarian cancer patients. Materials and Methods Forty consecutive patients underwent ¹⁸F-FDG-PET/CT at baseline and after one cycle of NAC. Metabolic responses were assessed by quantitative decrease in the maximum standardized uptake value (SUV_max) with PET/CT. Decreases in SUV_max were compared with cancer antigen 125 (CA-125) level before IDS, response rate by Response Evaluation Criteria in Solid Tumors criteria before IDS, residual tumor at IDS, and I chemotherapy response score (CRS) at IDS. Results A 40% cut-off for the decrease in SUV_max provided the best performance to predict CRS 3 (compete or near-complete pathologic response), with sensitivity, specificity, and accuracy of 81.8%, 72.4%, and 72.4%, respectively. According to this 40% cut-off, there were 17 (42.5%) metabolic responders (≥ 40%) and 23 (57.5%) metabolic non-responders (< 40%). Metabolic responders had higher rate of CRS 3 (52.9% vs. 8.7%, p=0.003), CA-125 normalization (< 35 U/mL) before IDS (76.5% vs. 39.1%, p=0.019), and no residual tumor at IDS (70.6% vs. 31.8%, p=0.025) compared with metabolic non-responders. There were significant associations with progression-free survival (p=0.021) between metabolic responders and non-responders, but not overall survival (p=0.335). Conclusion Early assessment with ¹⁸F-FDG-PET/CT after one cycle of NAC can be useful to predic response to chemotherapy before IDS in patients with advanced-stage ovarian cancer.