Molecular and Anatomic Imaging of Neuroendocrine Tumors.

Positron emission tomography (PET) with somatostatin receptor (SSTR) ligands has taken the lead in the imaging of neuroendocrine tumors (NETs). In this article, we review the role of SSTR PET scan in the management of NETs, including the indications for the scan, pitfalls in interpretation, and imaging selection criteria for peptide receptor radionuclide therapy. We also discuss the complementary role of fluorodeoxyglucose PET particularly for patients with high-grade disease.

The Impact of Radiopharmaceutical Therapy on Renal Function.

Radiopharmaceuticals used for cancer therapy are highly selective, designed to kill malignant cells and spare healthy tissues. Side effect rates are generally less than other treatments, but it is still the utmost concern to minimize normal organ toxicity and maximize radiation dose to the target lesions in applying radiopharmaceutical therapies (RPTs). Most commonly affected normal organs include bone marrow, kidneys and liver. The impact of RPTs to renal function is generally considered low. Peptide receptor radionuclide therapy (PRRT) using somatostatin radiopharmaceuticals, particularly 90Y-DOTATOC, has the potential to induce nephrotoxicity. This is because PRRT radiopharmaceuticals are primarily cleared thorough glomerular filtration and reabsorption/retainment of them at the renal proximal tubules exposes kidneys to additional radiation. Amino acid co-infusion is the standard regimen for competitive inhibition of tubular reabsorption of PRRT radiopharmaceuticals to mitigate nephrotoxicity. Other measures to protect renal function include hydration, use of plasma expander or radioprotectant, personalized renal dosimetry to limit renal radiation dose and close monitoring of renal function. Limited data suggest alpha emitter PRRT radiopharmaceuticals have less impact on kidney function compared to beta emitter PRRT, but more studies are needed for long term renal toxicity. 131I-MIBG is primarily excreted unchanged thorough the kidneys but renal absorbed dose is low and potential toxicities to the bone marrow and lungs are the most significant clinical concerns. Other RPTs that are not mainly cleared through kidneys such as 223Ra or radioimmunotherapy have no concern for kidney toxicity.