The prevalence and clinical significance of 68Ga-DOTANOC incidentaloma

With increased use of somatostatin analogue (SSA) PET/CT, the prevalence of incidentaloma - at present approximately 4.5% - is anticipated to rise. As malignancy has been reported in 13% of all cases, these incidentaloma are clinically relevant. However, because of publication bias, prevalence is probably underestimated and the malignancy rate overestimated. Therefore, we assessed the prevalence, cause, malignancy rate, and tracer uptake intensity on 68Ga-DOTANOC PET. All 68Ga-DOTANOC PET/CT protocols in adults, performed between 2017 and 2024 at Antwerp University Hospital, were retrospectively screened for incidentaloma. Patient records were examined to determine the cause of non-physiological increased tracer uptake. A total of 1,951 68Ga-DOTANOC PET/CTs were performed in 1,102 subjects. A total of 145 incidentaloma (13.2%) were described in 136 subjects (mean age 64 ± 13 years; F/M 82/54), most commonly in the thyroid (n = 43), brain (n = 31), prostate (n = 23), and breast (n = 11). The cause of pathological tracer uptake was evaluated by additional imaging in 55% of incidentaloma, whereby benign thyroid nodules, meningioma, benign prostatic hyperplasia, and breast fibroma and carcinoma were the most common findings, respectively. The malignancy rate was low (6%), comprising two breast cancers, one prostate cancer, one renal cell carcinoma, and one lung cancer. This is the largest single-centre study describing the prevalence and cause of 68Ga-DOTANOC incidentaloma to date. While the prevalence is significantly higher (13.2%) than described in previous studies (4.5%), the malignancy rate was significantly lower (6 versus 13%), as was expected due to publication bias, and no thyroid cancer was diagnosed.