Molecular Profile of Metastatic Sporadic Medullary Thyroid Cancer (sMTC) Patients and Possible Correlation With Vandetanib Therapy

Medullary thyroid cancer (MTC) is considered worldwide a rare cancer. It derives from the parafolicular C-cells representing about 5-10% of all thyroid cancer. MTC is diagnosed as sporadic form (sMTC) in most of the patients, although in 20-30% of cases it could be hereditary and transmitted as an autosomal-dominant trait due to the germline mutations of the RET proto-oncogene. RET tyrosine kinase receptor is involved in the regulation of differentiation, proliferation, survival and cell motility processes through several intracellular signalling pathways, including MAPK and PI3K/AKT/mTOR pathways.

Vandetanib has been approved for patients with unresectable and/or metastatic MTC by the Food and Drug Administration, by the European Medicines Agency and, very recently, it has been licensed also by the Italian Regulatory Agency (AIFA) for the use in Italy. Vandetanib is an orally tyrosine kinase inhibitor (TKI) of vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR), and RET signaling. In a randomized phase III trial, response rate to vandetanib ranged from 31% to 55% with a predicted median progression-free survival (PFS) of 30.5 months while data on overall survival were still not available at the time of publication. These results suggest that approximately half of the patients could benefit from this compound whose activity is in every case limited in the time. Activity of vandetanib seems to be influenced by several factors, including RET mutational status and tumor genetic heterogeneity (clonal versus non-clonal RET mutation distribution). Recent analyses of circulating miRNAs in tumor patients have suggested that miRNA signatures may be useful as diagnostic/prognostic/predictive as well as pharmacodynamic markers for several tumor types.

No clinical neither biological data are currently available to identify which patients could really get a benefit from a TKI. In other words, some metastatic patients could suffer from an indolent disease, not requiring a TKI upfront and up to date, we are still not able to identify this selected group of patients Circulating miRNAs levels could be influenced by the treatment procedures, as it has been described in lung cancer where miR-21 and miR-24 resulted significantly lower in the post-operative period respect to the pre-operative one in paired samples. We hypothesize that a TKI therapy could influence the levels of circulating miRNAs as well.

Aim of this project is to seek non-invasive molecular markers potentially useful as prognostic tools for metastatic MTC patients.