Dual-Time-Point FDG Uptake Correlates with Prognostic Factors of Invasive Breast Cancer: Clinical Usefulness of Early Delayed Scanning

This study investigated correlations between fluorodeoxyglucose (FDG) uptake in tumors as assessed by modified dual-time-point (mDTP) FDG positron emission tomography/computed tomography (PET/CT) in invasive breast cancer (iBC) and several prognostic parameters. Thirty-two women who underwent mastectomies for iBC were retrospectively evaluated. mDTP scanning was performed using standard FDG PET/CT (PET1), followed by early delayed acquisition (PET2) without repositioning and additional CT scanning. Using maximal standardized uptake values on PET1 (SUV1) and PET2 (SUV2) in the primary breast tumor, the percentage changes between SUV1 and SUV2 (retention index, (RI)) were calculated. Prognostic parameters (e.g., tumor size and stage; number of metastatic lymph nodes; histologic grade; expression of estrogen receptor (ER), progesterone, epidermal growth factor receptor (HER-2), and p53; and the Ki-67 labeling index (LI)) were evaluated from the surgical specimens. PET2 scans were conducted 17.7 ± 1.5 min after PET1. RI values gradually increased as the histologic grade increased (p = 0.016), and were significantly higher when ER expression was absent (p = 0.023) and Ki-67 LI was high (p < 0.001). RI values also showed a moderately positive correlation with Ki-67 LI (r = 0.629; p < 0.001). RI correlated with well-known biologic prognostic factors of iBC and mDTP scanning, which could be used as a substitute for conventional DTP PET.