Prognostic and predictive role of the PI3K-AKT-mTOR pathway in neuroendocrine neoplasms

Neuroendocrine neoplasms (NENs) are considered a heterogeneous and rare entity. Its natural history is influenced by multiple clinicopathological characteristics, which guide the management of these patients. The development of molecular biology reveals that the PI3K-AKT-mTOR pathway plays a relevant role in tumorigenesis and progression of NENs. Mammalian target of rapamycin (mTOR) inhibitors, targeted agents that block this pathway, has improved outcomes in neuroendocrine tumors (NETs). Different therapeutic approaches, such as somatostatin analogs, chemotherapy, peptide receptor radionuclide therapy, and targeted agents, have shown benefits in the treatment of NETs. However, there are not any established prognostic or predictive biomarkers to select the best therapy option to individualize treatment. Although a relation between alterations in the PI3K-AKT-mTOR pathway and clinical outcomes has not been found, these anomalies are considered attractive biomarkers. Additional molecular analysis should be integrated in future clinical trials' design to identify potential predictive or prognostic biomarkers.

An Overview on the Sequential Treatment of Pancreatic Neuroendocrine Tumors (pNETs)

Patients suffering from pancreatic neuroendocrine tumors (pNETs) are now candidates to receive novel approved drugs that have demonstrated benefit in disease control rate and delay the time taken for tumor progression in Phase III clinical trials; for example, sunitinib, everolimus and lanreotide. Though pNETs represent a rare and heterogeneous disease, recent approaches are being taken to better understand the molecular pathways involved in carcinogenesis. Consequently, new treatment strategies are now available and others still under investigation show promising results. However, some questions around how to approach patients with pNETs are still unresolved, such as what the best sequence of treatments we can offer to each of our patients in the clinic at any time of their disease would be. Therapeutic decisions are, at the moment, guided by clinical judgment, based on different parameters coming from retrospective analysis and non-randomized clinical trials. However, advances in genomic research would lead to a more precise approach using therapeutic targets that would also allow the development of new agents, prognostic or predictive biomarkers and a better understanding of resistance mechanisms. The following article is a comprehensive review of the approved and investigational drugs in pNET, and highlights the current concerns about treatment sequencing, but also provides an update of some of the present and future efforts for an improvement in the therapeutic algorithm of the disease.

Pancreatic neuroendocrine tumors: approach to treatment with focus on sunitinib

Pancreatic neuroendocrine tumors (pNETs) are relatively rare malignancies. With secretory tumors such as insulinomas, vasoactive intestinal peptideomas, and gastrinomas, the hormone produced causes the symptom complex (e.g. hypoglycemia, peptic ulcer disease). With nonsecretory NETs, the clinical condition is determined by tumoral growth and metastasis. The course of metastatic pNETs may be indolent for several years but progression is often more rapid at later stages, leading to significant disability and a markedly negative impact on quality of life. Until recently, there were few effective systemic treatments for pNETs. Standard chemotherapy produces limited responses and has considerable toxicity. Somatostatin analogues control symptoms in some types of pNETs, but have not yet demonstrated antitumor activity. The recent introduction of targeted therapies, including the tyrosine kinase inhibitor sunitinib and the mammalian target of rapamycin inhibitor everolimus, yielded new opportunities for patients with advanced/metastatic pNETs. These drugs, which target key pathways in tumor proliferation and angiogenesis, provided clear clinical benefits in phase III clinical trials, including delayed tumor progression. The pivotal sunitinib phase III trial was discontinued prematurely due to higher rates of death and serious adverse events with placebo and greater progression-free survival (PFS) with sunitinib. In this trial, sunitinib demonstrated encouraging long-term responses as well as PFS and overall survival benefits, and an acceptable safety profile that allowed patients to preserve their quality of life. In every patient subgroup, including secretory and nonsecretory tumors, the hazard ratio for progression or death favored sunitinib. Circulating biomarkers are being investigated for the prediction and monitoring of responses to sunitinib. Although not fully evaluated in pNETs, biomarkers associated with response to sunitinib in several tumor types include soluble vascular endothelial growth factor receptor 2 and 3, interleukin 8, and stromal cell-derived factor 1α. Based on recent data, treatment algorithms have been updated for advanced and metastatic pNETs.