Preoperative 18F-FDG PET/CT for CT-Guided Biopsy Planning: Predicting Target Adjustment and Improving Malignant Yield in Large Tumors

Objective To assess the clinical utility of preoperative 18F-FDG PET/CT for CT-guided biopsy planning of large tumors, including predictors of PET-driven target adjustment and malignant yield with FDG hotspot targeting in very large tumors. Methods In this retrospective single-center study, we analyzed 82 patients who underwent CT-guided biopsy between January 2015 and December 2025 with preoperative 18F-FDG PET/CT performed within 90 days before biopsy. Target adjustment was defined as changing the planned intratumoral biopsy target from the contrast-enhanced CT–based target to an alternative intratumoral site based on FDG uptake. Tumor size was evaluated by ROC analysis. Multivariable logistic regression included age, sex, tumor size, PET system (analog vs digital), ΔSUVmax, lesion location (chest vs other), and lymphoma (vs other). In tumors ≥ 52 mm, malignant yield was compared between hotspot (highest uptake) and non-hotspot targeting. Results Target adjustment was performed in 28/82 cases (34.1%). Interobserver agreement was 89% with Cohen’s κ = 0.74 (95% CI, 0.58–0.89). Tumor size predicted target adjustment (AUC 0.847; 95% CI 0.761–0.934), and the Youden-optimal cutoff was 52 mm (sensitivity 0.82, specificity 0.81). Target adjustment rates were 5/49 (10.2%) for < 52 mm and 23/33 (69.7%) for ≥ 52 mm (p < 0.001). In multivariable analysis, tumor size (per 10 mm) was independently associated with target adjustment (OR 2.33; 95% CI 1.56–3.50; p < 0.001), while female sex (OR 0.20; 95% CI 0.03–0.91; p = 0.049) and lymphoma (OR 0.082; 95% CI 0.0058–0.746; p = 0.041) were inversely associated. The multivariable model showed good discrimination (AUC 0.90; 95% CI 0.82–0.98; DeLong). Among tumors ≥ 52 mm, malignant pathology was obtained in 14/14 cases (100%) with hotspot targeting versus 5/9 (55.6%) with non-hotspot targeting (p = 0.014). Conclusions Preoperative 18F-FDG PET/CT supports CT-guided biopsy planning of large tumors by identifying cases likely to require target adjustment and by improving malignant yield when the FDG hotspot is targeted in tumors ≥ 52 mm.