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, SUV_max 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.