Accuracy of a new diagnostic tool in deep infiltrating endometriosis: pET-CT with [18F]-FES

Abstract

Background: Diagnosis of deep infiltrating endometriosis (DIE) remains a challenge. The preoperative workup is generally limited especially in the evaluation of extra-genital and extra-pelvic disease and in distinguishing between previous surgical scar and active lesion so that the laparoscopy and histology verification is still considered to be the gold standard for the diagnosis of the disease. We proposed to evaluate the performance of positron emission tomography (PET-CT) with a sperimental tracer of estrogen receptor (16α-[18F]fluoro-17β-estradiol-[18F]-FES-) for the non-invasive diagnosis and staging of this ubiquitous, estrogen-dependent disease. Primary endpoint of the study was to evaluate the feasibility of this tool comparing its accuracy with the histology. Secondary endpoint was to compare the accuracy of [18F]-FES PET-CT with that of magnetic resonance imaging (MRI). Methods: Four eligible patients with extra-genital DIE without hormonal treatment for at least 2 spontaneous mestrual cycles were enrolled in this sperimental study. On “Step 1” (third menstrual day of the second spontaneous cycle), patient underwent an abdominal-pelvic MRI with contrast agent after a blood sampling with dosage of hormonal profile. On “Step 2” (after menstruation and before the 15th day of the second cycle) the same eligible patient underwent an abdominal-pelvic [18F]-FES PET-CT scan. On “Step 3” (within 30 days from the [18F]-FES PET-CT) patient underwent nerve-sparing laparoscopic complete excision of endometriosis. During surgery, 9 anatomical areas were systematically assessed for each patient. Findings of [18F]-FES PET-CT and RMI were compared by a region-by-region analysis to surgical histological biopsies obtained from laparoscopy, standard of reference in our study. Results: In total 40 anatomical regions were examined; 8 were positive on [18F]-FES PET-CT, 4 were positive on RMI and 9 were positive on histology. A total of 10 regions were discordant on [18F]-FES PET-CT and RMI. Nine out of 10 (90%) discrepant findings demonstrated agreement between [18F]-FES PET-CT and histology. Conclusion: Preliminary data of this pilot sperimental study indicated that [18F]-FES PET-CT might be superior to RMI and other current diagnostic tools in detecting endometriosis. [18F]-FES PET-CT showed greater accuracy not only for the extra-genital and extra-pelvic regions but also for genital ones, mainly in patients with previous surgery in which it is difficult to discriminate surgical scar from an active endometriotic lesion. Further studies are needed to investigate its role in case of endometriosis of bowel in different sites than recto-sigmoid, nervous localizations, subcentimetrical disease and endometriomas. If such data will be confirmed on large series, we maybe could think to avoid surgery only for diagnostic purposes; or unnecessary surgery in patients [18F]-FES negative; or simply we will be able to better plan the surgery.