Therapeutic strategy in unresectable metastatic colorectal cancer: an updated review

Systemic therapy is the standard care for patients with unresectable advanced colorectal cancer (CRC), but salvage surgery of metastatic disease should be considered in the case of adequate tumor shrinkage. Several drugs and combinations are now available for use in treating patients with advanced CRC, but the optimal sequence of therapy remains unknown. Moreover, the administration of antitumor therapy can be modulated by periods of maintenance or treatment breaks rather than delivered as full therapy until disease progression or unacceptable toxicity, followed by reintroduction of prior full therapy when required, before switching to other drugs. Consequently, randomized strategy trials are needed to define the optimal treatment sequences. Molecular testing for Kirsten rat sarcoma viral oncogene homolog (KRAS) and neuroblastoma RAS viral oncogene homolog (NRAS) is mandatory but not sufficient to select appropriate patients for epidermal growth factor receptor (EGFR) monoclonal antibody (MoAb) therapy.

Overcoming resistance to antiangiogenic therapies

The concept of targeting new blood vessel formation, or angiogenesis, in tumors is an important advancement in cancer therapy, resulting, in part, from the development of such biologic agents as bevacizumab, a monoclonal antibody directed against vascular endothelial growth factor (VEGF)-A. The rationale for antiangiogenic therapy is based on the hypothesis that if tumors are limited in their capacity to obtain a new blood supply, so too is their capacity for growth and metastasis. Additional evidence suggests that pruning and/or "normalization" of irregular tumor vasculature and reduction of hypoxia may facilitate greater access of cytotoxic chemotherapy (CT) to the tumor. Indeed, for metastatic colorectal cancer, bevacizumab in combination with established CT regimens has efficacy superior to that of CT alone. Despite ~2-month longer progression-free and overall survival times than with CT alone, patients still progress, possibly because of alternative angiogenic "escape" pathways that emerge independent of VEGF-A, or are driven by hypoxic stress on the tumor. Other VEGF family members may contribute to resistance, and many factors that contribute to the regulation of tumor angiogenesis function as part of a complex network, existing in different concentrations and spatiotemporal gradients and producing a wide range of biologic responses. Integrating these concepts into the design and evaluation of new antiangiogenic therapies may help overcome resistance mechanisms and allow for greater efficacy over longer treatment periods.

Bevacizumab-based therapies in the first-line treatment of metastatic colorectal cancer

Since its approval for the first-line treatment of metastatic colorectal cancer (mCRC), bevacizumab has become a standard treatment option in combination with chemotherapy for patients with mCRC. Bevacizumab has demonstrated efficacy in combination with a number of different backbone chemotherapy regimens, and its widespread use has introduced several important questions regarding the selection and optimization of bevacizumab-based treatment regimens, its use in various patient populations, and the identification of associated adverse events. This review discusses the results of several phase II and phase III clinical trials, as well as large observational studies, to address the use of bevacizumab in the treatment of patients with mCRC in the first-line setting.

Therapeutic strategy in unresectable metastatic colorectal cancer

While surgery is the cornerstone treatment for early-stage colorectal cancer, chemotherapy is the first treatment option for metastatic disease when tumor lesions are frequently not fully resectable at presentation. Mortality from colon cancer has decreased over the past 30 years, but there is still a huge heterogeneity in survival rates that can be mainly explained by patient and tumor characteristics, host response factors, and treatment modalities. The management of unresectable metastatic colorectal cancer is a global treatment strategy, which applies several lines of therapy, salvage surgery, maintenance, and treatment-free intervals. The individualization of cancer treatment is based on the evaluation of prognostic factors for survival (serum lactate dehydrogenase level, performance status), and predictive factors for treatment efficacy [Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation status]. The available treatment modalities for metastatic colorectal cancer are chemotherapy (fluoropyrimidine, oxaliplatin, irinotecan), anti-angiogenic agents (e.g. bevacizumab), and anti-epidermal growth factor agents (cetuximab, panitumumab). The increasing number of active compounds dictates the strategy of trials evaluating these treatments either in combination or sequentially. Alternative outcomes that can be measured earlier than overall survival are needed to shorten the duration and reduce the size and cost of clinical trials.

Personalized colon cancer care in 2010

Colon cancer (CC) therapies have improved patient outcomes significantly over the last decades in both the adjuvant and metastatic settings. With the introduction of a number of novel agents, both traditional chemotherapies and biologically targeted agents, the need to identify subgroups that are likely and not likely to respond to a particular treatment regimen is paramount. This will allow patients who are likely to benefit to receive optimal care, while sparing those unlikely to benefit from unnecessary toxicity and cost. With the identification of several novel biomarkers and a variety of technologies to interrogate the genome, we already are able to rapidly study patient tumor or blood samples and normal tissues to generate a large dataset of aberrations within the cancer. How to digest this complex information to obtain accurate, reliable, and meaningful results that will allow us to provide truly personalized care for CC patients is just starting to be addressed. In this article, we briefly review the history of CC treatment, with an emphasis on current clinical standards that incorporate a "personalized medicine" approach. We then review strategies that will potentially improve our ability to individualize therapy in the future.