Intra-arterial radiopeptide therapy of hepatic metastases of neuroendocrine tumors: a systematic review

Purpose: Hepatic metastases represent a frequent manifestation of systemic involvement of neuroendocrine tumors and, respectively, neuroendocrine cancers. In the last decade, therapeutic advances could be achieved using radiopeptide receptor-based therapies with 90Y-and 177Lu-radioligands as systemic therapy of this disease. As these conjugates are usually administered intravenously, only few medical centers so far have elucidated the potential benefits of administering these compounds intra-arterially with regard to more specific and effective hepatic treatment of these metastases. It is the aim of this review to provide a concise summary of to date literature on radiopeptide receptor therapy with special focus on intra-arterial administration. Methods: We conducted search in PubMed, Google Scholar and Cochrane databases to identify studies using intra-arterial administration (i.a.) of radiopeptide receptor therapies in neuroendocrine tumors. Results: The used therapeutic procedures vary with regard to the used isotopes (e.g., 177Lu/90Y, 111In, 213Bi). Overall, the available evidence points to the fact that i.a. application of, e.g., 177Lu/90Y-DOTATOC causes an objective response rate which varies between 53 and 60% in i.a. application studies, whereas objective response in i.v. application studies published so far with various PRRT ligands cumulates to a maximum of 30%. Conclusion: Intra-arterial radiopeptide receptor therapy using 177Lu or 90Y for hepatic metastases of neuroendocrine tumors is a well-tolerated treatment option in patients suffering from multiple, non-resectable hepatic metastases. Since both loco-regional and systemic effects can be achieved by intra-arterial application of peptide-labeled radioactive isotopes, notably symptom control and treatment response seem to be superior to systemic i.v. protocols. The presented cohorts are nonetheless too small and treatment protocols too heterogenous to allow for an objective comparison.