Influence of lanreotide on uptake of Ga-DOTATATE in patients with neuroendocrine tumours: a prospective intra-patient evaluation.

INTRODUCTION

Somatostatin receptor imaging with PET is the standard of care for patients with a neuroendocrine tumour (NET). Since therapy and imaging with somatostatin analogues utilize the same receptor, current guidelines recommend withdrawing long-acting somatostatin analogues for 3-4 weeks prior to somatostatin receptor PET imaging. The aim of this study is to prospectively assess the effect of lanreotide use on the uptake of Ga-DOTATATE intra-individually 1 day prior to and 1 day post injection of lanreotide.

METHODS

Thirty-four patients with metastatic and/or unresectable NET and currently on lanreotide therapy for at least 4 months were included in the study. A Ga-DOTATATE PET/CT scan was performed on the day before and the day after lanreotide injection. In each patient Ga-DOTATATE uptake (SUV, , ) was assessed in both tumour lesions and normal tissue. All scans were assessed by two blinded nuclear medicine physicians for visual analysis. Paired T-tests were performed to determine the differences between the scans.

RESULTS

Of the 34 patients included, 31 were available for analyses in which 190 tumour lesions were measured. Uptake of Ga-DOTATATE in tumour lesions was increased significantly after lanreotide, but decreased significantly in the liver, spleen, and thyroid gland resulting in a higher tumour-to-liver ratio.

CONCLUSION

Lanreotide injection prior to Ga-DOTATATE PET/CT does not result in decreased tumour uptake. In contrast, tumour uptake was increased, whereas the uptake in normal organs is decreased, leading to an increased tumour-to-liver ratio. However, these differences were small and not deemed clinically relevant. These results strongly suggest that discontinuation of lanreotide injections in the weeks prior to Ga-DOTATATE PET examinations is unnecessary and does not compromise nuclear medicine imaging results.