Emerging paradigms in the development of resistance to tyrosine kinase inhibitors in lung cancer

The success of tyrosine kinase inhibitors (TKIs) in select patients with non-small-cell lung cancer (NSCLC) has transformed management of the disease, placing new emphasis on understanding the molecular characteristics of tumor specimens. It is now recognized that genetic alterations in the epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) define two unique subtypes of NSCLC that are highly responsive to genotype-directed TKIs. Despite this initial sensitivity, however, the long-term effectiveness of such therapies is universally limited by the development of resistance. Identifying the mechanisms underlying this resistance is an area of intense, ongoing investigation. In this review, we provide an overview of recent experience in the field, focusing on results from preclinical resistance models and studies of patient-derived, TKI-resistant tumor specimens. Although diverse TKI resistance mechanisms have been identified within EGFR-mutant and ALK-positive patients, we highlight common principles of resistance shared between these groups. These include the development of secondary mutations in the kinase target, gene amplification of the primary oncogene, and upregulation of bypass signaling tracts. In EGFR-mutant and ALK-positive patients alike, acquired resistance may also be a dynamic and multifactorial process that may necessitate the use of treatment combinations. We believe that insights into the mechanisms of TKI resistance in patients with EGFR mutations or ALK rearrangements may inform the development of novel treatment strategies in NSCLC, which may also be generalizable to other kinase-driven malignancies.

Targeting mechanisms of resistance to anti-EGF receptor therapy in KRAS wild-type colorectal cancer: the path to more personalized medicine

The targeting of EGF receptors (EGFRs) in metastatic colorectal cancer has improved the outcome of patients with KRAS wild-type tumors. However, these improvements have been modest and do not translate across all patients with KRAS wild-type tumors. Better understanding of the EGFR pathway has led to the exploration of variable novel potential biomarkers of resistance and response to anti-EGFR therapy. This manuscript will focus on recently identified mechanisms of resistance to anti-EGFR therapy in KRAS wild-type colorectal cancer. Subsequently, an assessment will be presented on how the current understanding of some of these mechanisms of resistance has led, and will lead, to novel therapeutic opportunities in the management of colorectal cancer.

Epidermal growth factor receptor tyrosine kinase inhibitor-resistant disease

PURPOSE

EGFR-mutant lung cancer was first described as a new clinical entity in 2004. Here, we present an update on new controversies and conclusions regarding the disease.

METHODS

This article reviews the clinical implications of EGFR mutations in lung cancer with a focus on epidermal growth factor receptor tyrosine kinase inhibitor resistance.

RESULTS

The discovery of EGFR mutations has altered the ways in which we consider and treat non-small-cell lung cancer (NSCLC). Patients whose metastatic tumors harbor EGFR mutations are expected to live longer than 2 years, more than double the previous survival rates for lung cancer.

CONCLUSION

The information presented in this review can guide practitioners and help them inform their patients about EGFR mutations and their impact on the treatment of NSCLC. Efforts should now concentrate on making EGFR-mutant lung cancer a chronic rather than fatal disease.