Whether [18F]FDG PET/CT radiomic features provide information on tumor proliferation beyond conventional PET parameters remains uncertain. We investigated their associations with Ki-67 in untreated primary breast carcinoma using a predefined panel of technically reproducible features. This retrospective, single-center study included 42 women and 19 radiomic features previously selected based on interobserver reproducibility and redundancy, independently of Ki-67. Associations with continuous Ki-67 were evaluated using Spearman correlations, permutation tests, bootstrap confidence intervals, and false discovery rate (FDR) correction, alongside four conventional PET parameters. Five radiomic features showed significant associations with Ki-67 after FDR correction. The strongest association was observed for firstorder_90Percentile (ρ = 0.556; 95% CI, 0.279–0.745; q = 0.002), comparable to that of SUVmax (ρ = 0.565). However, none of these five associations remained significant after adjustment for metabolic tumor volume (MTV), SUVmax, or both, followed by FDR correction. Excluding six small lesions attenuated the correlations for both SUVmax (ρ = 0.440) and firstorder_90Percentile (ρ = 0.427). Although several radiomic features were associated with Ki-67, an independent contribution beyond conventional PET parameters was not demonstrated. These findings require confirmation in independent cohorts.
