18F-FLT Positron Emission Tomography/Computed Tomography Imaging in Pancreatic Cancer: Determination of Tumor Proliferative Activity and Comparison with Glycolytic Activity as Measured by 18F-FDG Positron Emission Tomography/Computed Tomography Imaging

Abstract

Objective:This phase-I imaging study examined the imaging characteristic of 3’-deoxy-3’-(18F)-fluorothymidine (18F-FLT) positron emission tomography (PET) in patients with pancreatic cancer and comparisons were made with (18F)-fluorodeoxyglucose (18F-FDG). The ultimate aim was to develop a molecular imaging tool that could better define the biologic characteristics of pancreas cancer, and to identify the patients who could potentially benefit from surgical resection who were deemed inoperable by conventional means of staging.Methods:Six patients with newly diagnosed pancreatic cancer underwent a combined FLT and FDG computed tomography (CT) PET/CT imaging protocol. The FLT PET/CT scan was performed within 1 week of FDG PET/CT imaging. Tumor uptake of a tracer was determined and compared using various techniques; statistical thresholding (z score=2.5), and fixed standardized uptake value (SUV) thresholds of 1.4 and 2.5, and applying a threshold of 40% of maximum SUV (SUVmax) and mean SUV (SUVmean). The correlation of functional tumor volumes (FTV) between 18F-FDG and 18F-FLT was assessed using linear regression analysis.Results:It was found that there is a correlation in FTV due to metabolic and proliferation activity when using a threshold of SUV 2.5 for FDG and 1.4 for FLT (r=0.698, p=ns), but a better correlation was obtained when using SUV of 2.5 for both tracers (r=0.698, p=ns). The z score thresholding (z=2.5) method showed lower correlation between the FTVs (r=0.698, p=ns) of FDG and FLT PET.Conclusion:Different tumor segmentation techniques yielded varying degrees of correlation in FTV between FLT and FDG-PET images. FLT imaging may have a different meaning in determining tumor biology and prognosis.

PET Imaging in Pancreatic Cancer

“…18 F-FLT, an analogue of thymidine, can be performed for clinical evaluation and quantification of proliferative activity and tumor invasiveness. There many clinical researches evaluated the potential value of 18 F-FLT PET/CT for imaging pancreatic adenocarcinoma [2,9,10]. Quon et al [9] compared 18 F-FLT and 18 F-FDG PET/CT scan in five patients.…”

“…Pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic cancer, which is currently considered to be the third leading cause of cancerrelated deaths in the United States [1]. Only 10 to 20% of patients with pancreatic cancer are candidates for resection and hence have any potential for cure, and the majority of patients present in late stages [2]. Conventional diagnostic imaging, such as ultrasonography and endoscopic ultrasound (EUS), Computed tomography (CT), MRI (Magnetic Resonance Imaging) are available structual imaging techniques for the diagnosis, staging, and management of pancreatic neoplasms.…”

The clinical application of 18F-FDG PET/CT in pancreatic cancer: a narrative review

“…Currently, imaging techniques commonly used for pancreatic cancer include endoscopic ultrasound (EUS), conventional ultrasound, magnetic resonance imaging (MRI), multidetector spiral computed tomography (MDCT), positron emission tomography/computed tomography (PET/CT), and others ( 10 , 11 ). PET/CT is a new imaging device composed of PET and CT ( 12 ). 18-Fluorodeoxyglucose ( 18 F-FDG) is a commonly used tracer in the clinic ( 13 ).…”

Fluorothymidine Positron Emission Tomography (FLT-PET) Repeatability and Response Evaluation in Advanced Pancreatic Cancer Patients Treated with Gemcitabine-Based Chemotherapy

“…The imaging of FLT trapping and accumulation in cells using FLT-PET represents TK1 activity, which is thought to be proportional to cellular proliferation and DNA synthesis by the salvage pathway [11,15,16]. The physiologic uptake of FLT by the liver, kidneys, and bladder, leading to a high background signal, has limited the use of FLT in some indications [17][18][19]. As FLT and gemcitabine, one of the primary chemotherapeutic agents for the treatment of PDAC, are both transported into the cell via the human equilibrative nucleoside transporter-1 (hENT1), FLT-PET has been postulated as a potential biomarker of gemcitabine uptake [19][20][21][22].…”