Endocrine Abstracts

Introduction: Over the past years Ga-68-DOTANOC PET/CT is increasingly performed, which may lead to an increase in encountering incidentaloma. In 2022, a systematic review was published about incidentaloma on Ga-68-DOTANOC/DOTATE, describing a prevalence of 4.5% and a relatively high rate of malignancy (13%). However, it was estimated that the overall prevalence was underestimated and the frequency of malignancy overestimated because of publication bias.

Methodology: The result of Ga-68-DOTANOC PET/CT’s performed in adults between 2017 and 2022 in the Antwerp University Hospital were retrospectively screened for incidentaloma (= an increased, non-physiological uptake of the isotope, not related to the indication for imaging).

Results: 1240 Ga-68-DOTANOC PET/CT’s were performed in 804 subjects. In total, 127 incidentaloma were diagnosed in 115 subjects with a mean age of 64±13 years and F/M ratio of 68/47. The most frequently reported locations of incidentaloma were the thyroid (n=24), brain (n=23) and prostate (n=21), followed by the spleen (n=18), breast (n=12), stomach (n=8), uterus (n=4), liver (n=2), pancreas (n=2), esophagus (n=2), kidney (n=2), ovarium (n=1) and mediastinum (n=1). In 33 (26%) incidentaloma no further investigations were performed. Rate of malignancy was 5% (3 breast cancers, 2 renal cell carcinomas and 1 prostate cancer). Increased isotope uptake in the brain, thyroid, prostate and spleen were most frequently caused by meningioma (n=15), benign nodules (n=4), benign prostate hypertrophy (n=8) and accessory spleen (n=16), respectively.

Conclusion: This is the largest single-center study describing the prevalence and etiology of Ga-68-DOTANOC incidentaloma to date. Evaluating the images of 804 subjects a prevalence of 16% was found which is higher than the prevalence of 4.5% earlier described in the systematic review of Bentestuen et al. The difference can be explained by the inclusion of accessory spleen in our study and the systematic review including studies focusing on incidentaloma in one specific organ. Incidentaloma were most frequently encountered in the thyroid (19%), followed by the brain (18%) and prostate (17%). The rate of malignancy in this study was 5%, which is lower than the rate of 13% described in the systematic review, possibly secondary to the inclusion of case reports with the tendency to publish the exceptional. No thyroid cancer was diagnosed in this study, however 67% of the thyroid incidentaloma did not underwent an ultrasound. With this abstract we want to stimulate other centers to publish their frequency of incidentaloma on Ga-68-DOTANOC PET/CT which may help in interpretation.