Predictive factors of response to mTOR inhibitors in neuroendocrine tumours.

Medical treatment of neuroendocrine tumours has drawn a lot of attention due to the recent demonstration of efficacy of several drugs on progression free survival, including somatostatin analogs, small tyrosine kinase inhibitors and mTOR inhibitors (or rapalogs). The latter are approved as therapeutic agents in advanced pancreatic neuroendocrine tumors and have been demonstrated to be effective in different types of neuroendocrine tumors, with variable efficacy due to the development of resistance to treatment. Early detection of patients that may benefit from rapalogs treatment is of paramount importance in order to select the better treatment and avoid ineffective and expensive treatments. Predictive markers for therapeutic response are under intensive investigation, aiming at a tailored patient management and more appropriate resource utilization. This review summarizes the available data on the tissue, circulating and imaging markers that are potentially predictive of rapalog efficacy in neuroendocrine tumours.