Sorafenib and sunitinib

A review of tumour lysis syndrome with targeted therapies and the role of rasburicase

WHAT IS KNOWN AND OBJECTIVE

Tumour lysis syndrome (TLS) is an oncologic emergency with potentially devastating consequences classically associated with cytotoxic chemotherapy. In recent years, molecularly targeted drugs have assumed an increasingly important role in cancer therapeutics. The possibility of TLS is often overlooked in this setting. Rasburicase, a recombinant urate oxidase, is remarkably effective in treating hyperuricemia, thought to be central to the pathogenesis of renal injury in TLS. Our objective is to review the literature on TLS especially as it pertains to targeted therapies and summarize current knowledge and provide future directions regarding the role of rasburicase in the management of TLS.

METHODS

A MEDLINE search was conducted using PubMed and the keyphrase 'tumor lysis syndrome' to identify articles describing TLS with a broad range of novel anti-cancer agents. Meeting abstracts were also reviewed. Additionally, the biomedical literature was searched using the keyword 'rasburicase'.

RESULTS AND DISCUSSION

Tumour lysis syndrome has been described with nearly every class of 'targeted therapy'. This is not surprising as any drug causing death of cancer cells by any mechanism may lead to TLS in the appropriate setting. Although there is a wealth of evidence suggesting that rasburicase is extremely effective in correcting hyperuricemia, prospective trials showing that it improves hard outcomes such as acute renal failure, need for dialysis and mortality are lacking. Furthermore, much lower doses and durations of therapy than approved appear to be effective in controlling hyperuricemia, potentially leading to enormous cost savings.

WHAT IS NEW AND CONCLUSION

Any effective cancer therapy can lead to TLS. Physicians should consider the risk of TLS on a case-by-case basis and determine appropriate prophylaxis. The role of rasburicase continues to evolve. Randomized controlled trials evaluating clinically relevant outcomes are needed.

[Management of side-effects of targeted therapies in renal cancer: gastrointestinal side-effects]

Several types of gastrointestinal complications can occur during treatment with targeted therapies: diarrhoea, nausea and vomiting, abnormalities in hepatic and pancreatic profiles, etc. Gastrointestinal problems in targeted therapy can have a significant impact on the general status of patients, their weight and their adherence to the treatment. The prevention, screening and rapid treatment of these side-effects are essential elements of patient care and can limit the associated dose reductions and loss of therapeutic benefit. In the case of diarrhoea, treatment must be started at the onset of grade 1 or 2 diarrhoea (four to six stools per day), with loperamide or racecadotril. Treatment with targeted therapy must be stopped if there is diarrhoea of grade 3 or 4 (more than six stools per day). In the case of nausea/vomiting or burning pain in the oesophagus, symptomatic treatment without stopping the targeted therapy is recommended. Biological assessment including transaminases, total and conjugated bilirubin should be prescribed before treatment initiation with targeted therapy. An elevation in alkaline phosphatases without elevation of transaminases suggests primarily the existence of hepatic metastases. In the event of worsening of the hepatic profile, if ALT greater than 5N, treatment must be stopped and specialist advice sought.

Targeting angiogenesis in childhood sarcomas

Angiogenesis and vasculogenesis constitute two processes in the formation of new blood vessels and are essential for progression of solid tumors. Consequently, targeting angiogenesis, and to a lesser extent vasculogenesis, has become a major focus in cancer drug development. Angiogenesis inhibitors are now being tested in pediatric populations whereas inhibitors of vasculogenesis are in an earlier stage of development. Despite the initial enthusiasm for targeting angiogenesis for treatment of cancer, clinical trials have shown only incremental increases in survival, and agents have been largely cytostatic rather than inducing tumor regressions. Consequently, the role of such therapeutic approaches in the context of curative intent for childhood sarcomas is less clear. Here we review the literature on blood vessel formation in sarcomas with a focus on pediatric sarcomas and developments in targeting angiogenesis for treatment of these rare cancers.

Drug development for cancer chemoprevention: focus on molecular targets

With biomolecular evidence accumulating at an exponential rate, there will be a surge in the development of targeted cancer prevention drugs and interventions in the next decade. Promising results from clinical treatment trials identify a spectrum of targeted cancer therapies in several broad categories. These include both small molecule inhibitors of either key receptors or enzyme binding sites, as well as intravenously delivered monoclonal antibodies that block a specific binding interaction between ligands and their receptors. These targeted interventions conform to a basic translational algorithm: biomarker present, biomarker modulated, and biomarker clinically relevant. A review of solid tumor targets provides a manageable list of factors that are critical to cancer cell survival. As such, these targets represent factors that are not only clinically relevant but also may play a critical role in early tumor development prior to the evolution of frank invasive malignancy. This possibility qualifies these targets for consideration in the development of cancer prevention interventions. Among solid tumors, the treatment of breast cancer with targeted drugs has a long record benchmarked by the initial US Food and Drug Administation (FDA) approval of tamoxifen for metastatic breast cancer treatment in 1977. Since then, the list of oncology drug targets has expanded to include aromatase, androgen receptor, the epidermal growth factor receptor (EGFR) family, and others. It is not surprising that tamoxifen was the first of the modern targeted therapies to be approved for cancer risk reduction and additional approvals are anticipated. The focus of this review is the pharmacologic manipulation of targets within epithelial tumor cells and the implication of those targets for intervening to suppress and eliminate premalignant cells in human tissue. Major obstacles to prevention drug development can be addressed by attention to two important areas. One of these is the refinement of early phase prevention trials to identify drug targets in epithelial cells that are at demonstrated risk of evolving into cancer cells, ie, cells from a developmental niche in cancer ontogeny. Early results suggest that molecular risk signatures may allow the investigational identification of molecular targets in premalignant tissue, with the possibility that chemoprevention agents can be used to eliminate the risk signature. To the extent that this approach can be developed, it will allow for cancer risk reduction in a way that is analogous to the measurement of tumor response to treatment. Even with improvements in the efficiency of clinical trials that come from using molecular risk signatures, there is an ever-growing list of chemoprevention agents that are candidates for evaluation. Improved prevention drug screening methodologies are therefore needed to prioritize agents for clinical testing. In addition to drug targets located in epithelial tumor cells, another list of malignancy-associated targets could be generated by considering targets in tumor-associated stromal and endothelial cells (eg, fibroblast growth factor [FGF], vascular endothelial growth factor [VEGF]), as well as targets related to a systemic reservoir of circulating cells that can be recruited to carcinogenic influence by inflammatory factors such as nuclear factor (NF)kappaB. The complementarities of target-related processes within tumors cells, in the tumor microenvironment, and beyond suggests that there is great potential for multi-targeted approaches that may be more effective than single agents and also less prone to resistance. Additional options, related to drug dose and schedule, remain to be established. As long as multiple agents can be used in combination for optimal effect with acceptable toxicity, the co-targeting of the epithelial cell compartment along with other compartments of oncogenic activity is expected to expand the dimensions of targeted prevention and enhance the overall opportunity to eliminate precancer or cells at risk of eventually transitioning to invasive cancer.