Surrogate Predictive Biomarkers for Response to Anti-EGFR Agents: State of the Art and Challenges

The epidermal growth factor receptor (EGFR) plays a key role in cancer development and progression in several human malignancies including non-small cell lung cancer (NSCLC). Several strategies aimed at inhibiting the EGFR have been investigated in the last years, including the use of small tyrosine kinase inhibitors (TKIs) directed against the intracellular domain of the receptor and monoclonal antibodies targeting its extracellular portion. Subgroups of patients who are more likely to respond to TKIs have been identified based on both clincal and biological features. Never-smoking history has emerged as the most relevant clinical characteristic predictive of response to TKIs in NSCLC, while presence of drug-sensitive EGFR mutations and EGFR gene gain represent critical biological variables associated with an improved outcome for patients exposed to these agents. Recent studies have highlighted the existence of biological factors involved in intrinsic and acquired resistance to TKIs, including k-ras, HER-2 and EGFR exon 20 mutations. Increasing knowledge of EGFR biology and drug-receptor interactions will allow to identify individuals who are likely to derive a clinical benefit from the proposed targeted therapy, sparing refractory patients expensive and potentially toxic treatment.

Mutational analysis in cytological specimens of advanced lung adenocarcinoma: a sensitive method for molecular diagnosis

INTRODUCTION

The discovery that somatic mutations in the epidermal growth factor receptor (EGFR) gene are associated with sensitivity to the EGFR tyrosine kinase inhibitors (TKIs) in lung adenocarcinomas, whereas Kras mutations are associated with resistance, has generated excitement among both clinicians and researchers studying non-small cell lung cancer (NSCLC). Mutational analysis may soon be very useful in choosing among a wide range of targeted therapies to individualize treatment to tumor characteristics. This analysis would be even more useful in patients with advanced NSCLC, in whom cytological specimens are often the only material available.

METHODS

We analyzed 23 archived cytologic specimens of advanced/metastatic lung adenocarcinomas for mutations in EGFR exons 18 to 21, and Kras exon 2.

RESULTS

Our data show that our cytological specimens were perfectly adequate for the molecular analysis of EGFR and Kras mutations. EGFR TK domain mutations were found in three cases (13.04%) and were associated with both female gender (p = 0.02) and a nonsmoking history (p = 0.008). Moreover, we explored the relationship between EGFR mutation status and the presence of Kras mutations. Kras mutations involving codon 12 in exon 2 were found in 5 (21.73%) of the 23 adenocarcinomas and were associated, where known, with smoking habits. We never found EGFR alterations in tumors with Kras mutations.

CONCLUSIONS

Our results provide oncologists with a highly accurate laboratory method to identify biological predictors of the efficacy of different therapies, and they may have an important impact on clinical practice. This method may be particularly useful in patients with advanced/metastatic NSCLC.

Understanding the new genetics of responsiveness to epidermal growth factor receptor tyrosine kinase inhibitors

The epidermal growth factor receptor (EGFR) is implicated in cancer progression and development and, being overexpressed in a variety of human malignancies, is an attractive target for selective anticancer therapy. EGFR tyrosine kinase inhibitors (TKIs) have been demonstrated to produce dramatic and durable responses in a fraction of non-small cell lung cancer patients. During the last few years, clinical and biological predictors for TKI sensitivity have been identified. Among clinical features, never-smoking history seemed the most critical factor, probably because of the different spectrum of molecular abnormalities associated with cigarette-smoking exposure. Among biological predictors, several studies indicate that EGFR mutations and increased EGFR gene copy number are implicated in response to TKI therapy, with conflicting results in survival. Mutations in the EGFR gene as well as in K-ras and HER2 genes seemed to impair TKI effects, leading to TKI resistance. Because most available data come from retrospective studies, there is an urgent need to validate these results in prospective trials. Several studies have been recently completed, and these data could indicate how to properly select patients who are candidates for TKI therapy.