Hepatocellular carcinoma: systemic therapies and future perspectives

Hepatocellular carcinoma is (HCC) the most common primary malignancy of the liver in adults. It is also the fifth most common solid cancer worldwide and the third leading cause of cancer-related deaths. Treatment options for HCC include liver transplantation, surgical resection, locoregional therapies and chemotherapy. The median survival time of patients following the diagnosis of unresectable disease is approximately 6-20 months, whereas the 5-year survival is less than 5%. Given the projected increase in incidence of HCC due to hepatitis C virus infection and obesity related cirrhosis, there is an urgent need for more intensive research in this cancer. In this article, we review the systemic options available for patients with HCC, its molecular pathogenesis and future therapeutic directions with special emphasis on immune-based and molecularly-targeted therapy.

New agents on the horizon in hepatocellular carcinoma

Despite the successful approval and extensive application of sorafenib, the prognosis for patients with advanced hepatocellular carcinoma (HCC) remains poor. Fortunately, there have been renewed and continued interests and active research in developing other molecularly targeted agents in HCC during the past few years. While there is early evidence of antitumor activity of several agents in phase I/II studies, phase III efforts with a few targeted agents have failed, highlighting the challenges of new drug development in HCC. This review summarizes the current status of other molecularly targeted agents under development in advanced HCC.

Clinical activity of mammalian target of rapamycin inhibitors in solid tumors

The phosphatidylinositol 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) pathway is vital for cell metabolism, growth, and proliferation. mTOR is frequently upregulated in many tumor types and hence has become an important target in cancer treatment. Sirolimus and its derivatives (rapalogs) interact with the intracellular receptor FK506 binding protein 12 (FKBP12), forming a complex with high affinity for mTOR and thus disrupting its activity. Rapalogs are being evaluated extensively in cancer patients with different formulations and schedules. Significant clinical activity has led to their approval for the treatment of kidney cancer, mantle cell lymphoma, and subependymal giant cell astrocytoma; however, despite increasing knowledge about cancer cell biology, their activity in other malignancies is unclear. Further research is needed to identify optimal dosage, administration and targeted combination as well as the subset of patients likely to respond to mTOR/PI3K inhibition. This review focuses on a discussion of the pathway, its implications in cancer biology and results of clinical trials of rapalogs alone or in combination, organizing them by common malignancy type.

Molecular targeted therapy for advanced hepatocellular carcinoma: current status and future perspectives

Sorafenib, a multikinase inhibitor targeting vascular endothelial growth factor (VEGF)-mediated angiogenesis, is the first drug found to prolong survival of patients with advanced hepatocellular carcinoma (HCC). This advance has shifted the paradigm of systemic treatment for HCC toward molecular targeted therapy (MTT). However, the disease-stabilizing effect of VEGF signaling-targeted MTT normally lasts only for a few months, suggesting a rapid emergence of resistance in the majority of patients. To overcome the resistance to VEGF signaling-targeted MTT, strategies incorporating inhibition of either compensatory pro-angiogenic pathways or recruitment of bone marrow-derived circulating endothelial progenitors, as well as suppression of other oncogenic pathways, are currently being investigated. The combination of multiple molecular targeted agents or the use of multi-target agents may enhance the efficacy at the expense of increased toxicities. To facilitate the development of MTT for HCC, current methodologies for pharmacodynamic assessment, patient selection and target identification need to be improved. Patient selection according to the individual molecular signature of the tumor and correlative biomarker studies are encouraged while planning a clinical trial of novel MTT.

The present and the future landscape of treatment of advanced hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly lethal disease that is resistant to conventional cytotoxic drugs. Historically, effective systemic treatment options have not been available for patients with unresectable advanced disease. However, an improved understanding of the molecular mechanisms that regulate tumor initiation and progression over the past few years has led to the development of novel molecularly-targeted therapies that specifically block the different cellular signaling pathways involved. Recently, the antiangiogenesis and Raf kinase inhibitor, sorafenib showed a survival advantage in advanced stage HCC in two randomized, double-blind, controlled trials. These positive results were the first to demonstrate the efficacy of molecularly-targeted therapies in advanced HCC. Moreover, results from phase I and II trials evaluating other agents in this disease are promising and are under active clinical development. In the near future, we expect to have more data, knowledge, and evidence regarding the use of molecularly-targeted therapies in advanced HCC, both as single agents and in combination regimens. In this review, we will summarize the data concerning the present standard treatment for advanced HCC and discuss the newest, most promising clinical research that may affect the future treatment of this disease.

Systemic treatment of hepatocellular carcinoma: dawn of a new era?

PURPOSE AND DESIGN

Despite decades of efforts by many investigators, systemic chemotherapy or hormone therapy have failed to demonstrate improved survival in patients with advanced hepatocellular carcinoma (HCC). On the basis of placebo-controlled, randomized phase III trials, sorafenib has shown improved survival benefits in advanced HCC and has set a new standard for future clinical trials. The successful clinical development of sorafenib in HCC has ushered in the era of molecularly targeted agents in this disease, which is discussed in this educational review.

RESULTS AND CONCLUSION

Ongoing studies are evaluating the efficacy and tolerability of combining sorafenib with erlotinib and other targeted agents or chemotherapy. Many molecularly targeted agents that inhibit angiogenesis, epidermal growth factor receptor, and mammalian target of rapamycin are at different stages of clinical development in advanced HCC. Combining targeted agents that inhibit different pathways in hepatocarcinogenesis is an area of active investigation. Future research should continue to unravel the mechanism of hepatocarcinogenesis and to identify key relevant molecular targets for therapeutic intervention. Identification and validation of potential surrogate and predictive biomarkers holds promise to individualize patients' treatment to maximize clinical benefit and minimize the toxicity and cost of targeted agents. We hope that we will continue to improve the efficacy of systemic therapy in advanced HCC in the coming years.