Ga-DOTATATE PET imaging in clinically non-functioning pituitary macroadenomas.

Purpose: Clinically non-functioning pituitary macroadenomas (NFMA) have been reported to express somatostatin receptors (SSTR), but results are inconsistent across different studies. This may be related to limited sensitivity and specificity of techniques used to date, i.e. immunohistochemistry in surgical specimens and In-DTPA-octreotide scintigraphy in vivo. The aim of this study was to assess SSTR expression in NFMA in vivo using Ga-DOTATATE PET, which offers superior sensitivity and spatial resolution as compared with planar scintigraphy or SPECT.

Methods: Thirty-seven patients diagnosed with NFMA underwent Ga-DOTATATE PET/CT of the head in the framework of a randomised controlled trial assessing the effect of the somatostatin analogue lanreotide on NFMA size. Individual co-registered T1-weighted pituitary MRIs were used to assess Ga-DOTATATE uptake (SUV) in the adenoma. An SUV of > 2 was considered positive.

Results: Ga-DOTATATE uptake was positive in 34/37 patients (92%), with SUV of positive adenomas ranging from 2.1 to 12.4 (mean ± SD 5.8 ± 2.6).

Conclusions: This is the first report of Ga-DOTATATE PET performed in NFMA patients, demonstrating in vivo SSTR expression in the vast majority of cases. The high positivity rate when compared with results obtained with In-DTPA-octreotide scintigraphy probably reflects the superior sensitivity of PET imaging.

Trial Registration: Netherlands Trial Register, NL5136, registered on 18 August 2015; EudraCT, 2015-001234-22, registered on 10 March 2015, https://eudract.ema.europa.eu/.