Analysis of positron emission tomography/computed tomography in patients to differentiate between malignant transformation of endometrioma and endometrioma

Positron emission tomography in the evaluation of endometriosis: A systematic review

Despite the profound impact of endometriosis worldwide, delays in diagnosis and suboptimal surveillance techniques are well-recognised issues. Case studies have reported incidental uptake of 18F-FDG PET tracer in endometriotic lesions. However, the utility of PET imaging as a non-invasive diagnostic tool for endometriosis is currently unclear. The purpose of this systematic review was to summarise the existing evidence and determine the value of available PET scanning techniques in the detection and monitoring of endometriosis. MEDLINE, EMBASE, CENTRAL, SCOPUS and Web of Science were searched from conception to 05/03/23. Eligible studies included participants with a history of known or suspected endometriosis who underwent a PET scan for any indication. All PET tracers and protocols were eligible. Outcomes included correlation of PET tracer uptake with the presence of endometriosis seen at laparoscopy or confirmed on histology, sensitivity of tracer uptake, specificity of tracer uptake, site of lesions with tracer uptake, stage of lesions with tracer uptake, SUVmax of endometriosis lesions and adverse reactions to PET imaging. The protocol for this review was registered with PROSPERO (ID: CRD42023405260). Eight studies describing 110 participants were eligible for inclusion. Six studies assessed 18F-FDG with combined PET-CT, one study assessed 18F-FDG PET alone, and the remaining study assessed PET-CT with an alternative tracer, 68Ga-DOTATATE. For 18F-FDG imaging, the correlation of PET avidity with lesions or sites of endometriosis ranged from 0-55 %. Pre-operative 68Ga-DOTATATE PET-CT detected endometriosis in 33 % of cases. All included studies were cohort studies, six were assessed to have low risk of bias, one with moderate risk and one with high risk of bias. Overall, 18F-FDG PET scanning does not appear to consistently identify endometriotic lesions, and therefore its reliability and usefulness in endometriosis diagnosis is limited. The utility of 68Ga-DOTATATE PET-CT remains uncertain. Findings are constrained by limited available evidence reporting outcomes of PET imaging for endometriosis. Other existing PET tracers with biological plausibility in the detection or monitoring of endometriosis warrant further investigation.

PET/CT imaging in invasive endometriosis: a way to minimize missed diagnosis and reduce invasive interventions

INTRODUCTION

Heterogeneous and nonspecific symptoms make invasive endometriosis a difficult entity to diagnose. Small lesions with absent associated changes can be easily missed in cross-sectional imaging. Even when the lesions satisfy the thresholds for various investigations, their appearance changes with cyclical fluctuations in the hormonal levels. Therefore, newer approaches are needed to achieve correct diagnosis.

METHODS

Six females in reproductive age group (mean age = 32.5 ± 4.3 years) were retrospectively selected, wherein the diagnosis of invasive endometriosis was confirmed after 18F-FDG-PET/CT. Indications for PET/CT were staging in 4 patients, suspected progression in 1 and suspected inflammatory bowel disease in one patient. The study was repeated in proliferative phase in two patients and in the menstrual phase in another patient. FNAC was available in two patients and a drop in CA125 was documented in the last patient.

RESULTS

In five patients metabolically active lesions were seen in PET/CT and in the last, activity was absent despite symptoms. Repeat menstrual phase imaging in the last patient confirmed the diagnosis. In two patients with metabolically active lesions at baseline, resolution was seen in proliferative phase PET/CT. In the other two patients, repeat study was not indicated as FNAC revealed normal endometrial tissue and in the last patient, significant drop in CA125 was documented after just 2 weeks. In all of these patients, the final diagnosis was of invasive endometriosis.

CONCLUSION

In reproductive-age women, PET/CT acquisition should be optimized in the context of menstrual cycle. This approach can be used to non-invasively rule in/rule out endometriosis, especially with repeat imaging in proper menstrual phase.

Extrauterine Endometrial Stromal Sarcoma Mimicking Colorectal Cancer With Metastases

ABSTRACT

Extrauterine endometrial stromal sarcoma (EESS) is extremely rare, especially with the colorectum involvement. We describe 18 F-FDG PET/CT findings of EESS in the sigmoid colon and rectum in a 46-year-old woman who complained diarrhea. 18 F-FDG PET/CT revealed multiple hypermetabolic lesions in the abdomen and pelvis, including the sigmoid colon and rectum. Therefore, colorectal cancer with metastases was initially suspected; however, ultimately low-grade EESS was pathologically confirmed. Widespread EESS with intestine involvement revealed by 18 F-FDG PET/CT should be carefully distinguished from colorectal cancer with metastases.

Interference of Known or Suspected Endometriosis in Reporting FDG PET/CT Performed in Another Indication

INTRODUCTION

Endometriosis is a common gynecologic condition that may be visualized on 18F-FDG PET/CT and mimic lesions of malignancy. We analyzed the interference of known or suspected endometriosis in reporting 18F-FDG PET/CT performed in another indication.

RESULTS

The PET/CT images of 18 women with known (n = 15) or suspected (n = 3) endometriosis were analyzed. Based on clinical follow-up and results of other imaging, biopsy, and/or postsurgical histology, the presence of lesions of endometriosis at the time of 18F-FDG PET/CT was confirmed in 13 of 18 patients (72%). The per-patient positivity rate of 18F-FDG PET/CT was 8/18 (44%; 95% confidence interval, 22%-69%). The patient-based detection rate of 18F-FDG PET/CT in patients with confirmed lesions of endometriosis was 8/13 (62%; confidence interval, 32%-86%). On per-lesion/site basis, 18F-FDG PET/CT detected 11 of 20 sites (55%) of endometriosis. The SUVmax of these lesions/sites ranged between 1.8 and 5.3 (median, 3.8). In 9 of 18 patients (50%), a total of 13 non-endometriosis-related lesions/sites were detected by 18F-FDG PET/CT; their SUVmax ranged between 2.7 and 23 (median, 9.4).

CONCLUSION

The interference of known or suspected endometriosis in reporting 18F-FDG PET/CT performed in another indication was limited but possible and should be kept in mind, even in postmenopausal women, as the oldest patient with 18F-FDG-positive endometriosis was aged 63 years. The lesions of endometriosis showed inconstant 18F-FDG uptake with overlap of SUVmax with low-grade malignancies. In our series, the greatest SUVmax value of lesion of endometriosis was 5.3, somewhat higher than the threshold of 4 previously proposed for identification of malignant transformation of endometriosis.

PET Imaging for Gynecologic Malignancies

This review article summarizes the clinical applications of established and emerging PET tracers in the evaluation of the 5 most common gynecologic malignancies: endometrial, ovarian, cervical, vaginal, and vulvar cancers. Emphasis is given to 2-deoxy-2-[¹⁸F]fluoro-d-glucose as the most widely used and studied tracer, with additional clinical tracers also explored. The common imaging protocols are discussed, including standard dose ranges and uptake times, established roles, as well as the challenges and future directions of these imaging techniques. The key points are emphasized with images from selected cases.