Cabozantinib and vandetanib for unresectable locally advanced or metastatic medullary thyroid cancer: a systematic review and economic model

BACKGROUND

Medullary thyroid cancer (MTC) is a rare form of cancer that affects patients' health-related quality of life (HRQoL) and survival. Cabozantinib (Cometriq^®; Ipsen, Paris, France) and vandetanib (Caprelsa^®; Sanofi Genzyme, Cambridge, MA, USA) are currently the treatment modality of choice for treating unresectable progressive and symptomatic MTC.

OBJECTIVES

(1) To evaluate the clinical effectiveness and safety of cabozantinib and vandetanib. (2) To estimate the incremental cost-effectiveness of cabozantinib and vandetanib versus each other and best supportive care. (3) To identify key areas for primary research. (4) To estimate the overall cost of these treatments in England.

DATA SOURCES

Peer-reviewed publications (searched from inception to November 2016), European Public Assessment Reports and manufacturers' submissions.

REVIEW METHODS

A systematic review [including a network meta-analysis (NMA)] was conducted to evaluate the clinical effectiveness and safety of cabozantinib and vandetanib. The economic analysis included a review of existing analyses and the development of a de novo model.

RESULTS

The systematic review identified two placebo-controlled trials. The Efficacy of XL184 (Cabozantinib) in Advanced Medullary Thyroid Cancer (EXAM) trial evaluated the efficacy and safety of cabozantinib in patients with unresectable locally advanced, metastatic and progressive MTC. The ZETA trial evaluated the efficacy and safety of vandetanib in patients with unresectable locally advanced or metastatic MTC. Both drugs significantly improved progression-free survival (PFS) more than the placebo (p < 0.001). The NMA suggested that, within the symptomatic and progressive MTC population, the effects on PFS were similar (vandetanib vs. cabozantinib: hazard ratio 1.14, 95% credible interval 0.41 to 3.09). Neither trial demonstrated a significant overall survival benefit for cabozantinib or vandetanib versus placebo, although data from ZETA were subject to potential confounding. Both cabozantinib and vandetanib demonstrated significantly better objective response rates and calcitonin (CTN) and carcinoembryonic antigen (CEA) response rates than placebo. Both cabozantinib and vandetanib produced frequent adverse events, often leading to dose interruption or reduction. The assessment group model indicates that, within the EU-label population (symptomatic and progressive MTC), the incremental cost-effectiveness ratios (ICERs) for cabozantinib and vandetanib are > £138,000 per quality-adjusted life-year (QALY) gained. Within the restricted EU-label population (symptomatic and progressive MTC with CEA/CTN doubling times of ≤ 24 months), the ICER for vandetanib is expected to be > £66,000 per QALY gained. The maximum annual budget impact within the symptomatic and progressive population is estimated to be ≈£2.35M for cabozantinib and ≈£5.53M for vandetanib. The costs of vandetanib in the restricted EU-label population are expected to be lower.

LIMITATIONS

The intention-to-treat populations of the EXAM and ZETA trials are notably different. The analyses of ZETA subgroups may be subject to confounding as a result of differences in baseline characteristics and open-label vandetanib use. Attempts to statistically adjust for treatment switching were unsuccessful. No HRQoL evidence was identified for the MTC population.

CONCLUSIONS

The identified trials suggest that cabozantinib and vandetanib improve PFS more than the placebo; however, significant OS benefits were not demonstrated. The economic analyses indicate that within the EU-label population, the ICERs for cabozantinib and vandetanib are > £138,000 per QALY gained. Within the restricted EU-label population, the ICER for vandetanib is expected to be > £66,000 per QALY gained.

FUTURE RESEARCH PRIORITIES

(1) Primary research assessing the long-term effectiveness of cabozantinib and vandetanib within relevant subgroups. (2) Reanalyses of the ZETA trial to investigate the impact of adjusting for open-label vandetanib use using appropriate statistical methods. (3) Studies assessing the impact of MTC on HRQoL.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42016050403.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Clinical trial design in head and neck cancer: what has the oncologist learned?

Chemotherapy has assumed an important role in multidisciplinary management of patients with head and neck cancer. Much recent progress is attributable to successful design and careful implementation of clinical trials. In addition to showing the efficacy of chemotherapy, trials also instruct about how to improve experimental design so that we can make the most of what is learned. In this Personal View, several important studies in head and neck cancer are reviewed, with focus on issues raised by their design, potential solutions to these difficulties, and challenges that future investigations of this disease will face.

[Current status of therapeutic approaches with targeted therapies in malignant thyroid cancer. Highlights from the 2011 ASCO Congress]

Increasing interest in the treatment of locally advanced and already metastasized thyroid cancer is reflected in the high number of submitted and accepted conference papers at the annual meeting of the American Society of Clinical Oncology (ASCO Congress) 2011. Many patients suffering from differentiated, undifferentiated and medullary thyroid cancer do not respond to established therapeutic procedures, so that new strategies have to be developed. Targeted biological agents are a new and promising therapeutic method that selectively affects complex signaling cascades, especially angiogenesis, of the malignant cells. Clinicians and researchers should understand the potential of these therapeutic strategies and be aware of the typical side effects.

Kinase inhibitors for advanced medullary thyroid carcinoma

The recent availability of molecular targeted therapies leads to a reconsideration of the treatment strategy for patients with distant metastases from medullary thyroid carcinoma. In patients with progressive disease, treatment with kinase inhibitors should be offered.

Multikinase inhibitors: a new option for the treatment of thyroid cancer

Thyroid cancer typically has a good outcome following standard treatments, which include surgery, radioactive iodine ablation and treatment with TSH-suppressive levothyroxine. Thyroid cancers that persist or recur following these therapies have a poorer prognosis. Activation of mitogenic and angiogenic signaling pathways occurs in these cancers, and preclinical models have shown that inhibition of key kinase steps in these pathways can have antitumoral effects. Several of these kinase inhibitors have now been tested in phase II and phase III trials, with modestly encouraging results. Some promising data exist for the use of vandetanib (also known as ZD6474), motesanib, axitinib, cabozantinib (also known as XL184), sorafenib, sunitinib, pazopanib and lenvatinib (also known as E7080) in progressive thyroid cancer of medullary, papillary and follicular subtypes. These drugs are generally well-tolerated, although dose-limiting toxicities are common, and a few (probable) treatment-related deaths have been reported. Additional phase III trials will be needed to conclusively show that treatment benefit exceeds risk. Drug resistance can occur via activation of alternate mitogenic signals (pathway switching), as has been reported for the use of kinase inhibitors in other malignancies, such as melanoma. The hypothesis that combinations of kinase inhibitors targeting different pathways might produce better results is currently being tested in several clinical trials.

Targeted therapies for advanced thyroid cancer

PURPOSE OF REVIEW

Thyroid cancer incidence has significantly increased and the majority of cases are represented by differentiated thyroid carcinomas that are characterized by a very good prognosis. Nevertheless, after initial treatment up to 15% of patients present disease persistence or relapse and those with locally advanced or metastasized cancers that do not respond to established therapies ultimately risk death. This scenario has started to change following the development of molecular targeted therapies. This review will focus on the principles behind the use of these novel therapies and on the results of the most recent clinical trials with tyrosine kinase inhibitors (TKIs) and other targeted therapies in thyroid cancer.

RECENT FINDINGS

An understanding of the molecular events involved in cancer formation has prompted the development of numerous drugs that target key molecules implicated in angiogenesis and in the maintenance of the malignant phenotype of cancer cells. The results of several phase I and phase II studies and one phase III trial testing the efficacy of these drugs in advanced thyroid cancer are now available.

SUMMARY

Among the tested drugs, the TKIs sorafenib for differentiated thyroid carcinoma and vandetanib and XL184 for medullary thyroid carcinoma appear very effective and have reached phase III clinical trials. Second-generation TKIs and selective kinase inhibitors are showing even more promising profiles. Improved knowledge of the targets of the different drugs, combined with molecular profiling of the tumors to treat, will allow a tailored pharmacogenomic approach.

Novel molecular targeted therapies for refractory thyroid cancer

The incidence of thyroid cancer continues to increase and this neoplasia remains the most common endocrine malignancy. No effective systemic treatment currently exists for iodine-refractory differentiated or medullary thyroid carcinoma, but recent advances in the pathogenesis of these diseases have revealed key targets that are now being evaluated in the clinical setting. RET (rearranged during transfection)/PTC (papillary thyroid carcinoma) gene rearrangements, B-Raf gene mutations, and vascular endothelial growth factor receptor 2 (VEGFR-2) angiogenesis pathways are some of the known genetic alterations playing a crucial role in the development of thyroid cancer. Several novel agents have demonstrated promising responses. Of the treatments studied, multi-kinase inhibitors such as axitinib, sorafenib, motesanib, and XL-184 have shown to be the most effective by inducing clinical responses and stabilizing the disease process. Randomized clinical trials are currently evaluating these agents, results that may soon change the management of thyroid cancer.

Targeted therapies for thyroid tumors

Systemic chemotherapies for advanced or metastatic thyroid carcinomas have been of only limited effectiveness. For patients with differentiated or medullary carcinomas unresponsive to conventional treatments, novel therapies are needed to improve disease outcomes. Multiple novel therapies primarily targeting angiogenesis have entered clinical trials for metastatic thyroid carcinoma. Partial response rates up to 30% have been reported in single-agent studies, but prolonged disease stabilization is more commonly observed. The most successful agents target the vascular endothelial growth factor receptors, with potential targets including the mutant kinases associated with papillary and medullary oncogenesis. Two drugs approved for other malignancies, sorafenib and sunitinib, have had promising preliminary results reported, and are being used selectively for patients who do not qualify for clinical trials. At least one randomized, placebo-controlled phase III trial has been successfully completed, showing improved progression-free survival in patients with advanced or metastatic medullary thyroid carcinoma treated with vandetanib. Randomized trials for other agents are currently underway. Treatment for patients with metastatic or advanced thyroid carcinoma now emphasizes clinical trial opportunities for novel agents with considerable promise. Alternative options now exist for use of tyrosine kinase inhibitors that are well tolerated and may prove worthy of regulatory approval for this disease.

Targeting angiogenesis from multiple pathways simultaneously: BIBF 1120, an investigational novel triple angiokinase inhibitor

Angiogenesis is considered one of the major components of tumor progression and metastasis. Interfering with the formation and stabilization of tumor blood vessels could increase tumor response rates and may translate into improved clinical outcomes in cancer patients. The clinical efficacy demonstrated in phase III trials with bevacizumab, a monoclonal antibody that targets vascular endothelial growth factor ligand, suggests that targeting angiogenesis is a rational approach to cancer management. Agents that target additional proangiogenic intracellular signaling pathways also have the potential to contribute to our anticancer armamentarium. Novel targeted agents that have antiangiogenic properties have been developed in recent years such as sorafenib, sunitinib, vandetanib, and others. Many of them inhibit additional pathways beyond vascular endothelial growth factor signaling. One of these investigational targeted agents is a triple angiokinase inhibitor known as BIBF 1120. This compound targets not only vascular endothelial growth factor receptors, but also fibroblast growth factor receptors, and platelet-derived growth factor receptors. The preliminary clinical efficacy of BIBF 1120 is discussed in the context of the most relevant clinical data in several malignancies including non-small cell lung cancer.

Molecular Therapies in Thyroid Cancer

Thyroid cancer is a common diagnosis with greater than 34,000 cases per year in the United States. Early stage thyroid cancer is often managed with surgical intervention and radioactive iodine; however, for recurrent or metastatic disease, the treatment options, historically, have been limited to chemotherapy. Chemotherapy for metastatic thyroid cancer has been of limited efficacy. Encouragingly, molecular therapeutics have played a greater role in managing patients with advanced disease. These agents work primarily through disruption of tyrosine kinase pathways. This review will discuss the expanding role of molecular targets in managing patients with advanced thyroid cancer.

Targeting RET receptor tyrosine kinase activation in cancer

After ligand binding induces dimerization, the RET receptor tyrosine kinase activates multiple signal transduction pathways. Constitutively activating mutations and chromosomal rearrangements are the primary oncogenic event in a significant number of medullary thyroid cancers (MTC) and papillary thyroid cancers (PTC), respectively. When specific germline mutations in RET are identified early, prophylactic thyroidectomy can be timed to remove at-risk tissue in patients with multiple endocrine neoplasia 2 (MEN2) syndromes who would otherwise develop MTC. Conventional therapy for progressive metastatic MTC is limited. Small-molecule tyrosine kinase inhibitors can target multiple kinases at nanomolar concentrations, including RET, and have shown efficacy against a variety of malignancies. Initial clinical evidence suggests that several of these inhibitors, including sorafenib, vandetanib, motesanib, sunitinib, and XL-184, may have some benefit in treating progressive MTC. Although initial success seen in these trials seems to be modest, it represents a major breakthrough in the treatment of patients with widespread metastatic MTC.