Abstract PS13-50: Relationship of dedicated breast PET and MRI features in breast cancer patients receiving neoadjuvant chemotherapy
Authors: Hathi Deep K , Jones Ella F , Li Wen , Newitt David C , Guo Ruby , Seo Youngho , Flavell Robert R , Joe Bonnie N , Heditsian Diane , Brain Susie ,   ISPY-2 Imaging Working Group, ISPY-2 Consortium, Esserman Laura J , Hylton Nola M 
Published: February 2021

Abstract
Introduction: Dedicated breast positron emission tomography (dbPET) is an emerging imaging technique with the spatial resolution needed to assess functionality and intra-tumor heterogeneity in primary breast lesions. Breast cancer patients may benefit from dbPET imaging combined with molecularly targeted agents to non-invasively assess and predict response to targeted therapy in the neoadjuvant treatment setting. We have previously observed that [18F]-fluorodeoxyglucose (FDG) PET provides tumor metabolic information complementary to the angiogenic properties reflected by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for characterizing triple-negative breast cancers (TNBC) (1). In this study, we examined the relationship between FDG-dbPET and MRI features in a cohort of breast cancer patients receiving neoadjuvant chemotherapy (NAC).
Methods: With institutional review board approval, patients with biopsy-proven locally-advanced breast cancer were imaged with breast MRI and dbPET before (T0) and after three weeks (T1) of NAC. Standard DCE-MRI was obtained using a dedicated breast coil. Patients also underwent dbPET with 5 mCi of FDG at 45 minutes post-injection. Functional tumor volumes (FTV) were calculated from DCE-MRI by summing all voxels with an early percent enhancement (PE) exceeding 70% within a manually defined volume of interest (VOI). Maximum and mean PE (PEMax, PEMean) values within the VOI were also computed for analyses. Tumors were segmented in dbPET images using semi-automated threshold-driven methods. Body weight-corrected maximum and mean standardized uptake values (SUVMax, SUVMean), total lesion glycolysis (TLG), and metabolic tumor volume (MTV) were calculated for FDG-dbPET. Percent change relative to T0 (Δ = 100*(T1 - T0)/T0) was calculated for each feature. Spearman’s correlation coefficient was used to evaluate the relationship between MRI and dbPET features.
Results: Of the 16 patients enrolled in this study, 13 patients (N = 15 unique tumors) with MRI and dbPET at T0 and T1 were included in the analysis. 46% (6/13) of the patients had TNBC. Our initial findings indicated that ΔPEMax and ΔSUVMax had the highest correlation (ρ = 0.59, p = 0.022). FTV and TLG at T1 were also correlated (ρ = 0.56, p = 0.032). Among all imaging features, ΔMTV showed the largest post-treatment difference between TNBC (-54.5%) and non-TNBC (-6.06%) groups. Among MRI features, ΔFTV exhibited the largest difference between the groups: -70.4% in TNBC and -43.1% in non-TNBC. ΔSUVMax and ΔTLG were additional dbPET features with large differences between TNBC and non-TNBC patients (Table 1).
Conclusion: This exploratory study suggests that post-treatment ΔSUVMax and TLG provide complementary metabolic information to angiogenic properties (ΔPEMax and FTV, respectively) reflected by MRI. Other dbPET features may provide independent information adjunct to MRI for describing primary breast tumors. Patients with TNBC exhibited larger reductions in FDG uptake values and metabolic volume than non-TNBC patients. These observed reductions may improve early treatment response in patients with TNBC, enabling more precise treatment guidance. Further studies in larger cohorts are needed to validate these initial observations.
1. Bolouri MS, et al. Triple-Negative and Non-Triple-Negative Invasive Breast Cancer: Association between MR and Fluorine 18 Fluorodeoxyglucose PET Imaging. Radiology 2013;269:354-61
Comparison of ΔMRI and ΔFDG-dbPET in TNBC vs non-TNBC patientsAll Tumors (N = 15 tumors) Median(IQR)TNBC (N = 6 tumors) Median(IQR)non-TNBC (N = 9 tumors) Median(IQR)DCE-MRIΔFTV (%)-66.1 (-77.6, -19.1)-70.4 (-79.0, -62.1)-43.1 (-72.5, -2.95)ΔPEMax (%)-9.91 (-31.5, 19.5)-10.3 (-26.3, 24.2)-9.91 (-31.8, 8.42)ΔPEMean (%)-10.7 (-22.4, 2.77)-9.57 (-12.8, 0.29)-17.0 (-26.0, 2.33)FDG-dbPETΔSUVMax (%)-31.6 (-53.9, -20.6)-47.3 (-55.7, -41.1)-23.1 (-31.6, 1.13)ΔSUVMean (%)-34.1 (-65.4, -14.2)-48.5 (-74.6, -9.74)-34.1 (-44.5, -14.8)ΔMTV (%)-6.18 (-57.0, 38.5)-54.5 (-75.4, 15.3)-6.06 (-47.2, 38.9)ΔTLG (%)-64.9 (-75.2, 23.3)-75.2 (-84.0, -60.0)-47.9 (-65.2, 31.1)
Citation Format: Deep K Hathi, Ella F Jones, Wen Li, David C Newitt, Ruby Guo, Youngho Seo, Robert R Flavell, Bonnie N Joe, Diane Heditsian, Susie Brain, ISPY-2 Imaging Working Group, ISPY-2 Consortium, Laura J Esserman, Nola M Hylton. Relationship of dedicated breast PET and MRI features in breast cancer patients receiving neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS13-50.