Endocrine Abstracts

Introduction: Over the past years Ga-68 DOTANOC PET/CT is increasingly performed, which may lead to an increased finding of incidentaloma. In 2022, Bentestuen et al. published a systematic review concerning Ga-68 DOTA incidentaloma describing a prevalence of 4.5% with a malignancy rate of 13% (1). However, the rate of malignancy could have been overestimated because of publication bias.

Methodology : The results of Ga-68 DOTANOC PET/CT’s performed between 2017 and 2022 in adult patients in the Antwerp University Hospital were retrospectively screened for the presence of incidentaloma. An incidentaloma was defined as an increased, non-physiological uptake of the DOTA-tracer, not related to the indication for imaging. Primary the prevalence of incidentaloma was analyzed and secondary the underlying cause of increased uptake was investigated.

Results: 1240 Ga-68 DOTANOC PET/CT’s performed in 804 subjects were analyzed. A total of 109 incidentaloma were described in 102 subjects with a mean age of 64 ± 13 years and F/M ratio of 63/39. The most frequently reported locations of incidentaloma were the thyroid ( n = 24), brain ( n = 23) and prostate ( n = 21) followed by the breast ( n = 12), stomach ( n = 8), vertebra ( n = 7), uterus ( n = 4), liver ( n = 2), pancreas ( n = 2), esophagus ( n = 2), kidney ( n = 2), ovarium ( n = 1) and mediastinum ( n = 1). The underlying cause of increased tracer uptake was investigated in 76 (70%) incidentaloma. The most frequent incidentaloma in the thyroid, brain and prostate were thyroid nodules (7/9, NR 15), meningioma (15/18, NR 5), and benign prostate hypertrophy (8/13, NR 8), respectively. Rate of malignancy was 7.9% (6/76, NR 33) and consisted of 3 breast cancers, 2 renal cell carcinomas and 1 prostate cancer.

Conclusions: This is the largest single-center study describing the prevalence and underlying cause of Ga-68 DOTANOC incidentaloma to date. Evaluating the images of 804 subjects a prevalence of 13.6% was found which is higher than the prevalence of 4.5% previously described (1). This difference could be explained by the inclusion of studies only focusing on incidentaloma in one specific organ in the review of Bentestuen et al. Incidentaloma were most frequently encountered in the thyroid (22%), followed by the brain (21%) and prostate (19%). The rate of malignancy was low, 7.9%. This is lower compared to the rate of 13% previously described, which could be explained by the inclusion of case reports in the review of Bentestuen et al (publication bias). No thyroid cancer was diagnosed in this study population, however no work-up with ultrasound was performed in 67% of the thyroid incidentaloma. Malignancy rate of renal and breast incidentaloma were 100% and 25%, respectively. However this should be verified in a larger study population. With this abstract we want to stimulate other centers to publish/share their data of Ga-68 DOTA incidentaloma which can lead to a guidance in interpretation.

References:: 1. Bentestuen M, et al. Prevalence and significance of incidental findings on 68 Ga-DOTA-conjugated somatostatine receptor-targeting PET/CT: a systematic review of the literature. Cancer Imaging. 2022; 22: 44.