Systemic therapeutic strategies for GEP-NETS: what can we expect in the future?

Over the last few years, there have been important advances in the understanding of the molecular biology of neuroendocrine tumors (NETs) that have already translated into relevant advances in the clinic. Several studies have extensively assessed the mutational profile of NETs, and have shown the key roles that angiogenesis and the PI3K-AKT-mTOR pathway play in the pathogenesis of these tumors. Recent data has also revealed the potential relevance of transcription factors such as death domain-associated protein, x-linked mental retardation, and alpha-thalassemia syndrome protein or ataxia telangiectasia-mutated in NETs of pancreatic origin. This fast progress is leading to a rapidly increasing number of new agents being explored in the field of NETs. However, and despite some unquestionable success, objective remission rates remain low, and evidence of a substantial survival impact is lacking. Thus, there is an important need to improve our ability to identify patients most likely to benefit from specific therapies, and to incorporate biomarkers in the management of NETs. In addition, further efforts to understand mechanisms of escape and acquired resistance to the different available agents is of utmost importance, and will likely require performing paired tumor biopsies (prior and after treatment) or sequential sampling of surrogate tissues. Combinations of approved agents with new agents, either in a rational or biomarker-driven manner, are certainly warranted in this field. Likewise, sequential strategies to modulate and compensate for escape phenomenons are also of great interest. It should also be noted, however, that targeted agents are not innocuous and frequently yield toxicities that need to be adequately addressed by experienced specialists, particularly when drug combinations are considered. This review summarizes the salient data on biomarker and new agent development for the treatment of NETs.