Circulating miR-375 as a novel prognostic marker for metastatic medullary thyroid cancer patients

This study aimed to identify circulating miRNAs as novel non-invasive biomarkers for prognosis and vandetanib response in advanced medullary thyroid cancer (MTC) patients. We prospectively recruited two independent cohorts of locally advanced/metastatic MTC patients including a subgroup of vandetanib-treated subjects: a discovery cohort (n = 20), including matched plasma/tissue samples (n = 17/20), and a validation cohort, yielding only plasma samples (n = 17). Plasma samples from healthy subjects (n = 36) and MTC patients in remission (n = 9) were used as controls. MTC (n = 17 from 8 patients included in discovery cohort) and non-neoplastic thyroid specimens (n = 3) were assessed by microarray profiling to identify candidate circulating miRNAs. qRT-PCR and in situ hybridization were carried out to validate the expression and localization of a selected miRNA within tissues, and qRT-PCR was also performed to measure miRNA levels in plasma samples. By microarray analysis, we identified 51 miRNAs differentially expressed in MTC. The most overexpressed miR, miR-375, was highly expressed by C cells compared to other thyroid cells, and more expressed in MTC than in reactive C-cell hyperplasia. MTC patients had significantly higher miR-375 plasma levels than healthy controls (P < 0.0001) and subjects in remission (P = 0.0004) as demonstrated by qRT-PCR analysis. miR-375 plasma levels were not predictive of vandetanib response, but, notably, high levels were associated with significantly reduced overall survival (HR 10.61, P < 0.0001) and were a strong prognostic factor of poor prognosis (HR 6.24, P = 0.00025) in MTC patients. Overall, our results unveil plasma miR-375 as a promising prognostic marker for advanced MTC patients, to be validated in larger cohorts.

Chemotherapy and tyrosine-kinase inhibitors for medullary thyroid cancer

Medullary thyroid cancer (MTC) represents 3% of all clinical thyroid cancers and arises from thyroid C cells that produce calcitonin. Locally advanced or metastatic MTC requires a careful work-up including measurement of serum calcitonin and carcinoembryonic antigen, determination of their doubling time and comprehensive imaging to determine the extent of the disease, its aggressiveness, and the need for treatment. Cytotoxic chemotherapy can control tumor burden in some patients with response rates of around 20% in old series. For the last 10 years, systemic therapy for MTC patients with large tumor burden and documented progression of the disease has involved the use of tyrosine kinase inhibitors targeting VEGFR and ret. Progression-free survival benefits have been demonstrated for both vandetanib and cabozantinib, as compared to placebo. Although these molecules are effective, they also have specific toxicity profiles which require a thorough clinical management in specialized centers. In the present review, we describe the work-up and treatment modalities of patients with advanced or metastatic medullary thyroid cancer with a focus on chemotherapy and targeted therapy results.

Utility of proGRP as a tumor marker in the medullary thyroid carcinoma

Background:

Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor caused by a malignant transformation in the parafollicular C-cells of the thyroid, where calcitonin (CT) is released. Nowadays the main tumor markers (TM) used in the diagnosis and follow-up of MTC patients are CT and carcinoembryonic antigen (CEA). Nonetheless, progastrin releasing peptide (proGRP) has been recently proposed as a TM useful in the MTC. Our aims were to investigate the release of proGRP in thyroid tumors, its role in the assessment of advanced MTC and its utility in the differential diagnosis between MTC and non-MTC thyroid tumors.

Methods:

Serum samples from 22 patients with MTC and 16 with non-MTC were collected. Patients were classified into advanced cancer or no evidence of disease (NED). ProGRP was performed by Architect (Abbot Diagnostics), CT by Liaison (Diasorin) and CEA by Cobas E601(Roche Diagnostics).

Results:

ProGRP median concentration in advanced MTC was significantly higher (1398.4 pg/mL) when compared with non-MTC, either in advanced disease (24.9 pg/mL) or NED (14.6 pg/mL). In non-MTC patients, proGRP median concentration was below its cutoff level (50 pg/mL). Similar to CT, proGRP was able to detect 88.9% of MTC patients, but with a slightly lower specificity of 76.9%. Using proGRP together with CT the sensitivity increased to 100%.

Conclusions:

The low prevalence of this malignancy strongly recommends further collaborative studies, mainly focused on monitoring proGRP during tyrosine kinase inhibitors treatment for early detection of resistance and assessing its usefulness to avoid the observed false positive fluctuations that occur with CT and CEA.

Management of advanced medullary thyroid cancer

Medullary thyroid cancer arises from calcitonin-producing C-cells and accounts for 3-5% of all thyroid cancers. The discovery of a locally advanced medullary thyroid cancer that is not amenable to surgery or of distant metastases needs careful work-up, including measurement of serum calcitonin and carcinoembryonic antigen (and their doubling times), in addition to comprehensive imaging to determine the extent of the disease, its aggressiveness, and the need for any treatment. In the past, cytotoxic chemotherapy was used for treatment but produced little benefit. For the past 10 years, tyrosine kinase inhibitors targeting vascular endothelial growth factor receptors and RET (rearranged during transfection) have been used when a systemic therapy is indicated for large tumour burden and documented disease progression. Vandetanib and cabozantinib have shown benefits on progression-free survival compared with placebo in this setting, but their toxic effect profiles need thorough clinical management in specialised centres. This Review describes the management and treatment of patients with advanced medullary thyroid cancer with emphasis on current targeted therapies and perspectives to improve patient care. Most treatment responses are transient, emphasising that mechanisms of resistance need to be better understood and that the efficacy of treatment approaches should be improved with combination therapies or other drugs that might be more potent or target other pathways, including immunotherapy.

Integrating Murine and Clinical Trials with Cabozantinib to Understand Roles of MET and VEGFR2 as Targets for Growth Inhibition of Prostate Cancer

PURPOSE

We performed parallel investigations in cabozantinib-treated patients in a phase II trial and simultaneously in patient-derived xenograft (PDX) models to better understand the roles of MET and VEGFR2 as targets for prostate cancer therapy.

EXPERIMENTAL DESIGN

In the clinical trial, radiographic imaging and serum markers were examined, as well as molecular markers in tumors from bone biopsies. In mice harboring PDX intrafemurally or subcutaneously, cabozantinib effects on tumor growth, MET, PDX in which MET was silenced, VEGFR2, bone turnover, angiogenesis, and resistance were examined.

RESULTS

In responsive patients and PDX, islets of viable pMET-positive tumor cells persisted, which rapidly regrew after drug withdrawal. Knockdown of MET in PDX did not affect tumor growth in mice nor did it affect cabozantinib-induced growth inhibition but did lead to induction of FGFR1. Inhibition of VEGFR2 and MET in endothelial cells reduced the vasculature, leading to necrosis. However, each islet of viable cells surrounded a VEGFR2-negative vessel. Reduction of bone turnover was observed in both cohorts.

CONCLUSIONS

Our studies demonstrate that MET in tumor cells is not a persistent therapeutic target for metastatic castrate-resistant prostate cancer (CRPC), but inhibition of VEGFR2 and MET in endothelial cells and direct effects on osteoblasts are responsible for cabozantinib-induced tumor inhibition. However, vascular heterogeneity represents one source of primary therapy resistance, whereas induction of FGFR1 in tumor cells suggests a potential mechanism of acquired resistance. Thus, integrated cross-species investigations demonstrate the power of combining preclinical models with clinical trials to understand mechanisms of activity and resistance of investigational agents.

Progression of medullary thyroid cancer in RET carriers of ATA class A and C mutations

CONTEXT

There is no histopathological or radiological information on the natural course of tumor growth and lymph node metastasis in medullary thyroid cancer (MTC).

OBJECTIVE

This investigation aimed at determining annual rates of tumor growth and lymph node metastasis in hereditary MTC at the surgical pathology level.

DESIGN

This was a retrospective analysis.

SETTING

The setting was a tertiary referral center.

PATIENTS

Included were 172 carriers of American Thyroid Association (ATA) class C (95 patients) and class A rearranged during transfection (RET) mutations (77 patients) with MTC.

INTERVENTION

The intervention was compartment-oriented surgery.

MAIN OUTCOME MEASURES

Comparisons of means between index and nonindex patients yielded incremental primary tumor diameter and incremental number of lymph node metastases, which were divided by incremental patient age at tissue diagnosis.

RESULTS

Annual primary tumor growth was 0.4-0.5 mm in node-negative carriers of ATA class A and C mutations. In node-positive carriers, annual primary tumor growth was 2.6 mm (ATA class C mutations) and 1.2 mm (ATA class A mutations), more than 6-fold (2.6 vs 0.4 mm) and more than 2-fold greater (1.2 vs 0.5 mm) than in their node-negative peers. Node-positive carriers revealed an annual rate of lymph node metastasis of 0.6-0.7 nodes independent of ATA class.

CONCLUSIONS

Small MTCs may take longer than 10 years to become big enough to visualize on imaging. These slow growth rates highlight the importance of following up on patients for very long time periods to uncover at least some tumoral sources of persistent calcitonin production.