Impact of Cold Somatostatin Analog Administration on Somatostatin Receptor Imaging: A Systematic Review.

Purpose: The interactions between the administration of cold somatostatin analogs (cSAs) and their radiolabeled counterpart remain unclear, and discontinuation before imaging is still advised as a precaution. The aim of this systematic review is to evaluate the consequences of cSA administration on tumoral and surrounding healthy organs' uptake at somatostatin receptor (SSTR) imaging with SPECT or PET.

Methods: After registration of the study on Prospero (CRD42022360260), an electronic search of PubMed and Scopus databases was performed. Inclusion criteria were as follows: human patients referred for SSTR imaging for oncological purposes; at least 1 examination performed either before cSA administration or after a long-enough withdrawal of cSA treatment; at least 1 examination was performed under cSA treatment. Included articles were independently appraised by 2 authors using the standardized protocol provided by the Quality Assessment of Diagnostic Accuracy Studies. Discrepancies were solved by consensus.

Results: A total of 12 articles were included, 4 using 111In-pentetreotide and 8 using 68Ga-DOTA peptides. Administration of cSAs consistently resulted in decreased spleen and liver uptake (from 6.9% to 80% for spleen, 10% to 60% for liver) and increased tumor-to-background or tumor-to-healthy organ ratios. After cSA treatment, tumor uptake alone was unchanged or moderately decreased. Similar results were noted whether patient was octreotide-naive.

Conclusion: Impairment in SSTR imaging quality after cSA administration has not been demonstrated. On the contrary, the administration of cSAs seems to improve the contrast between tumoral lesions and the surroundings.