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

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.

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.

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.

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.