Abstract
PURPOSE: This study evaluates the semi-quantitative single-photon emission computed tomography (SPECT) parameters of prone SPECT using [(99m)Tc]Tc-sestamibi and compares them with Molecular Breast Imaging (MBI)-derived semi-quantitative parameters for the potential use of response prediction in women with locally advanced breast cancer (LABC). PROCEDURES: Patients with proven LABC with a tumor ≥ 2 cm on mammography and an indication for MBI using [(99m)Tc]Tc-sestamibi were prospectively enrolled. All patients underwent a prone SPECT/CT at 5 min (early exam) and an additional scan at 90 min (delayed exam) after injection of 600 MBq [(99m)Tc]Tc-sestamibi to compose wash-out rates (WOR). All patients underwent MBI after early SPECT/CT. Volumes of interest of the primary tumor were drawn semi-automatically on early and delayed SPECT images. Semi-quantitative analysis included maximum and mean standardized uptake values (SUV(max), SUV(mean),), functional tumor volume (FTV(SPECT)), total lesion mitochondrial uptake (TLMU), tumor-to-background ratios (TBR(max )and TBR(mean)), WOR and coefficient of variation (COV(SPECT)). Subsequently, the FTV(SPECT), TBR(SPECT) and COV(SPECT) were compared to FTV(MBI), TBR(MBI) and COV(MBI). RESULTS: Eighteen patients were included. Early SUV(max,) and TBR(max) showed significantly higher interquartile range (IQR) compared to SUV(mean) and TBR(mean), respectively 2.22 (2.33) g/mL, 6.86 (8.69), 1.29 (1.39) g/mL and 3.99 (5.07) (median (IQR), p < 0.05). WOR showed a large IQR (62.28), indicating that there is WOR variation among the LABC patients. FTV showed no difference between MBI and early SPECT semi-quantitative parameter (p = 0.46). CONCLUSIONS: In LABC patients it is feasible to obtain semi-quantitative parameters from prone SPECT/CT. The FTV derived from early prone SPECT/CT is comparable with MBI-based FTV. Studies with comprehensive clinical parameters are needed to establish the clinical relevance of these semi-quantitative parameters, including WOR, for response prediction before its use in clinical routine.