Measuring Estrogen Receptor Functionality using Progesterone Receptor PET Imaging: Rising to the (Estradiol) Challenge!

Abstract

218 Objectives: Several studies have shown that liver tumor burden (LTB), estimated by morphological modalities, such as CT and MR, is a significant factor for management and prognosis in patients with neuroendocrine tumors (NETs). PET/CT using 68Ga-DOTATOC or 18F-FDG, as a functional imaging tool, has been widely used in NETs, which might provide additional information for predicting prognosis. The aim of this study was to investigate the prognostic performance of DOTATOC-PET/CT and FDG-PET/CT in comparison to the morphological imaging modalities. Methods: We retrospectively analyzed 31 patients (male:female=17:14, 22-84 y.o.) with pancreatic NETs who had undergone DOTATOC-PET/CT and had been diagnosed to have liver metastasis by some imaging modalities. All patients had enhanced CT and/or MRI within a month of DOTATOC-PET/CT, and 26 patients FDG-PET/CT. We assessed LTB by a visual scale (0-10%, 10-25%, 25-50%, 50%-) on CT or MRI images. Then, we measured maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV) and total lesion uptake (TLU) on DOTATOC-PET/CT or total lesion glycolysis (TLG) on FDG-PET/CT for all metastatic liver tumors or all lesions in a whole body. In addition, the SUVmax ratio, MTV ratio, and TLU ratio, defined as a value in FDG-PET/CT divided by a value in DOTATOC-PET/CT, were calculated. The progression-free survival (PFS) and the overall survival (OS) were evaluated during their follow-up periods (8-83mo). The Kaplan-Meier analysis with the log-rank test was used to estimate and compare the correlation between each imaging parameter and PFS or OS. Results: On CT and/or MRI (n=31), LTB was significantly negatively correlated with PFS (p=0.003) and OS (p=0.007) [Fig. 1, 2]. On DOTATOC-PET/CT (n=31), 27 patients had DOTATOC-avid liver metastases and 30 patients had DOTATOC-avid lesions. The absence of DOTATOC-avid lesions was significantly negatively correlated with OS (p=0.041), although the number of the non-avid group was only one. Among the DOTATOC-PET/CT parameters, SUVmax, MTV, TLU for liver metastases and MTV for all lesions were significantly negatively correlated with PFS (p=0.003, p=0.005, p=0.006, p<0.001, respectively) [Fig. 3], but none was significantly correlated with OS. On FDG-PET/CT (n=26), 13 patients had FDG-avid liver metastases and 17 patients had FDG-avid lesions. The presence of FDG-avid liver metastases was significantly negatively correlated with PFS (p=0.011), and the presence of FDG-avid liver metastases or other lesions was negatively correlated with OS, without statistical significance. Among the FDG-PET/CT parameters, MTV, TLG for liver metastases and SUVmax for all lesions were significantly negatively correlated with PFS (p=0.005, p=0.005, p=0.007, respectively), and MTV and TLG for liver metastases were significantly negatively correlated with OS (p=0.047, p=0.047, respectively) [Fig. 4]. Among the ratio parameters, the MTV ratio for liver metastases was significantly negatively correlated with PFS (p=0.046), and the TLU ratio for all lesions was significantly negatively correlated with OS (p=0.014). Conclusions: Our data indicate that DOTATOC-PET/CT and FDG-PET/CT had a prognostic value in patients with liver metastases from pancreatic NETs. However, since DOTATOC-PET/CT and FDG-PET/CT demonstrated comparable prognostic performance with morphological imaging modalities, additional information was considered limited. Fig. 1 Kaplan-Meier curve for PFS stratified by LTB in CT and/or MRIFig. 2 Kaplan-Meier curve for OS stratified by LTB in CT and/or MRIFig. 3 Kaplan-Meier curve for PFS stratified by MTV for all lesions in DOTATOC-PET/CTFig. 4 Kaplan-Meier curve for OS stratified by TLG for liver metastases in FDG-PET/CT