"Who should receive epidermal growth factor receptor inhibitors for non-small cell lung cancer and when?"

OPINION STATEMENT

Inhibition of the epidermal growth factor receptor (EGFR) pathway in non-small cell lung cancer (NSCLC) is an exciting and rapidly evolving field. Erlotinib and gefitinib, two tyrosine kinase inhibitors (TKIs) of EGFR, have demonstrated activity in advanced NSCLC in the second- and third-line settings. Subset analyses of phase II and phase III clinical trials lead to the recognition that these two agents had more activity in certain subsets of NSCLC patients including never smokers, people of Asian descent and patients with EGFR FISH-positive or mutation-positive tumors. In particular, never smokers had statistically significant improvements in survival with either erlotinib or gefitinib therapy. Patients with EGFR FISH- or mutation-positive tumors had improved response rates to TKI therapy while those with KRAS mutant tumors did not derive any benefit. In the BR.21 trial treatment with erlotinib resulted in statistically significant improvements in overall survival and quality of life. Thus, while the question of who should receive EGFR TKI therapy is still not completely answered, all patients should be considered for erlotinib therapy in the second- or third-line setting. In daily clinical practice, there is currently no data to support the use of EGFR mutation or FISH status in this decision making process. Prospective trials are ongoing to determine which patient and tumor characteristics are predictive of a clinical benefit from TKI therapy.

Erlotinib: recent clinical results and ongoing studies in non small cell lung cancer

The epidermal growth factor receptor tyrosine kinase inhibitor erlotinib has shown to provide clinical benefit to patients with non-small cell lung cancer (NSCLC) after failure of front-line chemotherapy in a double-blind placebo-controlled clinical trial. More importantly, because of its unique mechanism of action, erlotinib seems to provide higher clinical benefit to specific subgroups of patients. The continued development of erlotinib in NSCLC is focused on the following areas: (a) validating clinical and molecular markers of clinical benefit in front-line therapy, (b) developing therapies for acquired and naturally resistant tumors, (c) revisiting combinations with chemotherapy, (d) developing combinations with antiangiogenesis agents, and (e) understanding the biological significance of the skin toxicity and developing rational approaches for its treatment. Clinical studies addressing these five areas are ongoing and are briefly described in this review.

The place of targeted therapy in the patient management of non-small cell lung cancer

There is much interest in the use of targeted therapies for the management of non-small cell lung cancer (NSCLC). To date, four targeted therapies - bevacizumab, cetuximab, erlotinib and gefitinib - have been investigated in randomised trials, in the treatment of advanced NSCLC. In the first-line setting, bevacizumab has been shown to significantly prolong survival when added to carboplatin/paclitaxel, as demonstrated in a large phase III study. However, issues of toxicity limit this treatment regimen to selected patients. The addition of bevacizumab to gemcitabine/cisplatin will be reported at ASCO 2007. The addition of cetuximab to cisplatin/vinorelbine has also been shown to improve survival in a randomised phase II study. Erlotinib has been investigated as monotherapy in first-line chemo-naïve patients and has demonstrated objective response rates of 10-23%. However, in a study comparing erlotinib versus chemotherapy, the outcome was less favourable for patients who had received erlotinib. Erlotinib monotherapy has also been investigated in recurrent disease, and has been shown to improve overall survival over that achieved with placebo. The greatest benefit was observed in never-smokers with epidermal growth factor receptor-positive tumours. In a further phase II randomised study, the effect of combining two targeted therapies has been investigated. This study compared erlotinib/bevacizumab versus bevacizumab/chemotherapy versus chemotherapy alone. Both regimens including targeted therapy were comparable and superior to chemotherapy alone. However, these are preliminary data and further research is required to clarify the role of targeted therapies in the management of advanced NSCLC.

Selecting Patients for Treatment with Epidermal Growth Factor Tyrosine Kinase Inhibitors

Identification of objective tumor regressions with epidermal growth factor receptor tyrosine kinases (EGFR TKI) in non-small cell lung cancer (NSCLC) patients has resulted in intense, worldwide clinical and basic research directed toward finding the optimal use of EGFR TKIs in NSCLC. EGFR TKI clinical trials have shown that higher response rates and longer survival are associated with specific patient characteristics and that using conventional chemotherapy simultaneously with EGFR TKIs in unselected patients does not increase survival. Molecular studies have revealed that EGFR-activating mutations and high EGFR gene copy number are frequently found in patients who have the best outcomes with EGFR TKIs. More recent studies suggest that KRAS mutations may identify the subset of patients who have the worst outcome with the EGFR TKI treatment. Currently, investigators are trying to determine the optimal approach to selecting patients for treatment with EGFR TKIs. Studies that have evaluated the potential predictive value of clinical features and/or molecular profiles in EGFR TKI-treated NSCLC patients are discussed in this review.

EGFR and HER2 gene copy number and response to first-line chemotherapy in patients with advanced non-small cell lung cancer (NSCLC)

BACKGROUND

A critical point in designing clinical trials comparing chemotherapy with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) in patients with non-small cell lung cancer (NSCLC) is the expected benefit with standard chemotherapy in presence of biological features indicative of TKI sensitivity. The aim of this study was to assess whether EGFR and HER2 gene copy number and Akt activation are associated with response to first-line chemotherapy.

METHODS

Tumor samples from 190 patients with NSCLC were analyzed. EGFR and HER2 gene copy number were evaluated by fluorescence in situ hybridization in 185 and 184 cases, respectively. Akt activation was assessed by immunohistochemistry (n = 176). Additional biomarkers included EGFR DNA sequencing (n = 65), and EGFR immunohistochemistry (n = 185).

RESULTS

Response rate was not associated with EGFR, HER2, and P-Akt status, irrespective of the method used for biomarker assessment. Among patients with EGFR gene mutations, response to chemotherapy was observed only in individuals with exon 19 deletion (response rate: 46.6% versus 0%, p = 0.02). Among the 190 patients analyzed, 123 received a treatment with a TKI as second- or third-line therapy. When assessed by fluorescence in situ hybridization or DNA sequencing, EGFR-positive patients seemed to be more sensitive to TKIs than to chemotherapy in terms of response rate and time to progression, whereas in EGFR-negative patients, response rate and time to progression favored chemotherapy.

CONCLUSION

This study suggested that EGFR expression and gene copy number, HER2 gene copy number, and P-Akt expression are not associated with response to first-line chemotherapy in NSCLC. Prospective phase III trials should compare standard chemotherapy with a TKI in selected NSCLC.