Boris G. Naraev

Current Status and Perspectives of Targeted Therapy in Well-Differentiated Neuroendocrine Tumors

Although neuroendocrine tumors (NET) are a relatively rare malignancy, the reported incidence is increasing, and some of the current treatment options are limited in their efficacy. Standard first-line therapy for metastatic small bowel NET includes somatostatin analogs. Although these agents can provide symptom relief and can delay disease progression in many patients, ultimately, new treatments are required for patients with progressive disease. In recent years, there has been considerable interest in developing agents specifically targeted against some of the pathways known to be involved in cancer cell growth, survival and invasion. In 2011, the mammalian target of rapamycin (mTOR) inhibitor everolimus and the tyrosine kinase inhibitor sunitinib were approved for the treatment of pancreatic NET. Clinical trials evaluating novel targeted agents are ongoing, both as single agents and in combination regimens. We review the current clinical status of these potential new treatments and highlight those with particular promise for the management of well-differentiated NET.

Comparison of Transarterial Liver-directed Therapies for Low-grade Metastatic Neuroendocrine Tumors in a Single Institution

Objective We compared the clinical outcomes of patients with metastatic neuroendocrine tumors treated with hepatic artery embolization (HAE), chemoembolization (HACE), and selective internal radiation therapy (SIRT) at our institution over the last 10 years. Methods The medical records of 42 patients with metastatic neuroendocrine tumors with hepatic metastases treated with HAE, HACE, or SIRT at the University of Iowa from 2001 to 2011 were analyzed. Results A total of 13 patients had HAE, 17 patients had HACE, and 12 patients had SIRT as their initial procedure. Time to progression (TTP) was similar between SIRT (15.1 months) and HACE/HAE groups (19.6 months; P = 0.968). There was a trend toward increased TTP in patients receiving HACE (33.4 months) compared with HAE (12.1 months) or SIRT (15.1 months), although not statistically significant (P = 0.512). The overall survival for all patients from the first intervention was 41.9 months. There was no difference between HACE/HAE and SIRT in posttherapy change of chromogranin A (P = 0.233) and pancreastatin (P = 0.158) levels. Time to progression did not correlate with the change in the posttherapy chromogranin A (P = 0.299) or pancreastatin (P = 0.208) levels. Conclusions There was no significant difference in TTP in patients treated with SIRT compared with patients treated with HAE or HACE. Baseline and posttherapy marker changes were not predictive of TTP.

Peptide Receptor Radionuclide Therapy Outcomes in a North American Cohort With Metastatic Well-Differentiated Neuroendocrine Tumors.

Objectives The objective of this study was to describe the outcomes of patients in the University of Iowa Neuroendocrine Tumor (NET) Database treated with peptide receptor radionuclide therapy (PRRT). Methods One hundred thirty-five patients from the University of Iowa NET Database who received PRRT were analyzed, their characteristics were described, and survival was calculated. Results The median age at diagnosis was 51 years, and 64% were men. The primary tumor was located in the small bowel (SBNET) in 37.8%, in the pancreas (PNET) in 26.0%, in the lung in 13.3%, in unknown primary in 9.6%, and in other sites in 13.3%. A radiographic response of any magnitude was observed in 65.8%, 11.1% had a mixed response, and 15.4% showed progression. The overall survival (OS) from the first PRRT was 40 months, and the median time to progression was 23.9 months. Higher pretreatment chromogranin A and pancreastatin levels predicted inferior OS. Conclusions Peptide receptor radionuclide therapy resulted in a relatively long OS and time to progression in heavily pretreated North American patients with advanced NETs. Elevated pretreatment chromogranin A and pancreastatin predicted shorter OS after therapy. Peptide receptor radionuclide therapy is a valuable treatment option in patients with advanced NETs, especially SBNETS.

Peptide receptor radionuclide therapy for patients with advanced pancreatic neuroendocrine tumors

177Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) is now approved for patients with advanced gastroenteropancreatic neuroendocrine tumors (NET), and it is therefore important to understand the efficacy and safety of PRRT in this patient population. PRRT efficacy and safety outcomes have frequently been summarized for patient populations with gastroenteropancreatic NET, but not specifically in patients with pancreatic NET (panNET). The pivotal phase 3 trial of 177Lu-DOTATATE PRRT in NET was restricted to patients with a midgut primary site. No phase 3 trial data on PRRT treatment outcomes are currently available for the panNET patient population. This review presents the available evidence for panNET treatment outcomes with PRRT and demonstrates that the available data favor PRRT as a modality for this NET primary site. However, several other therapies for advanced panNET are currently available, and the sequencing and combination of PRRT with these other therapies is set to become the big challenge for the future of panNET management. Patient, tumor, and logistical factors (tumor burden, expression of somatostatin receptors, availability of PRRT, patient preferences, and concerns over long-term toxicity) need to be taken into consideration when selecting therapy.