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.

Impact on disease-free survival of adjuvant erlotinib or gefitinib in patients with resected lung adenocarcinomas that harbor EGFR mutations

BACKGROUND

Patients with stage IV lung adenocarcinoma and epidermal growth factor receptor (EGFR) mutation derive clinical benefit from treatment with EGFR tyrosine kinase inhibitors (TKIs). Whether treatment with TKI improves outcomes in patients with resected lung adenocarcinoma and EGFR mutation is unknown.

METHODS

Data were analyzed from a surgical database of patients with resected lung adenocarcinoma harboring EGFR exon 19 or 21 mutations. In a multivariate analysis, we evaluated the impact of treatment with adjuvant TKI.

RESULTS

The cohort consists of 167 patients with completely resected stages I to III lung adenocarcinoma. Ninety-three patients (56%) had exon 19 del, 74 patients (44%) had exon 21 mutations, and 56 patients (33%) received perioperative TKI. In a multivariate analysis controlling for sex, stage, type of surgery, and adjuvant platinum chemotherapy, the 2-year disease-free survival (DFS) was 89% for patients treated with adjuvant TKI compared with 72% in control group (hazard ratio = 0.53; 95% confidence interval: 0.28-1.03; p = 0.06). The 2-year overall survival was 96% with adjuvant EGFR TKI and 90% in the group that did not receive TKI (hazard ratio: 0.62; 95% confidence interval: 0.26-1.51; p = 0.296).

CONCLUSIONS

Compared with patients who did not receive adjuvant TKI, we observed a trend toward improvement in DFS among individuals with resected stages I to III lung adenocarcinomas harboring mutations in EGFR exon 19 or 21 who received these agents as adjuvant therapy. Based on these data, 320 patients are needed for a randomized trial to prospectively validate this DFS benefit.

Phase I/II trial of cetuximab and erlotinib in patients with lung adenocarcinoma and acquired resistance to erlotinib

PURPOSE

In patients with epidermal growth factor receptor (EGFR) mutant lung adenocarcinoma, treatment with erlotinib or gefitinib is associated with a 75% radiographic response rate and progression-free survival of approximately 12 months. The most common mechanism of acquired resistance to erlotinib is development of a secondary mutation in EGFR, suggesting that these tumors continue to depend on EGFR signaling. We hypothesized that combined EGFR blockade would overcome acquired resistance to erlotinib in patients with lung adenocarcinoma. To evaluate the toxicity and efficacy of cetuximab and erlotinib in patients with acquired resistance to erlotinib, we conducted this phase I/II clinical trial.

EXPERIMENTAL DESIGN

Patients with lung adenocarcinoma and clinically defined acquired resistance to erlotinib were treated with erlotinib 100 mg daily, along with cetuximab every 2 weeks in three escalating dose cohorts (250 mg/m(2), 375 mg/m(2), and 500 mg/m(2)). The recommended phase II dose was then evaluated in a two-stage trial, with a primary end point of objective response rate.

RESULTS

A total of 19 patients were enrolled. The most common toxicities for the combination of cetuximab and erlotinib were rash, fatigue, and hypomagnesemia. The recommended phase II dose identified was cetuximab 500 mg/m(2) every 2 weeks and erlotinib 100 mg daily. At this dose and schedule, no radiographic responses were seen (0 of 13, 0%, 95% CI, 0-25).

CONCLUSIONS

Combined EGFR inhibition, with cetuximab 500 mg/m(2) every 2 weeks and erlotinib 100 mg daily, had no significant activity in patients with acquired resistance to erlotinib.

Pack-years of cigarette smoking as a prognostic factor in patients with stage IIIB/IV nonsmall cell lung cancer

BACKGROUND

This study was undertaken to characterize the relation between the survival of patients with stage IIIB/IV nonsmall cell lung cancer (NSCLC) and pack-years of cigarette smoking (graded according to the American Joint Committee on Cancer staging system).

METHODS

Data were analyzed from patients with stage IIIB/IV NSCLC who had completed a prospective smoking questionnaire. The impact of pack-years of cigarette smoking, age, sex, Karnofsky performance status (KPS), and the presence of weight loss >5% was evaluated on overall survival using univariate and multivariate analyses.

RESULTS

Smoking history and clinical data were available for 2010 patients with stage IIIB/IV NSCLC (1004 women and 1006 men). Approximately 70% of patients (1409 patients) had smoked >15 pack-years, 13% (270) were former and current smokers who had smoked < or = 15 pack-years, and 16% (331) were never-smokers (<100 lifetime cigarettes). Never-smokers had a longer median survival compared with former or current smokers (17.8 months vs 11.3 months; log-rank P < .001). Among smokers, patients with a < or = 15 pack-year history of smoking had a longer median survival than patients who had smoked >15 pack-years (14.6 months vs 10.8 months; log-rank P = .03). As the number of pack-years increased, the median overall survival decreased (log-rank P < .001). Multivariate analysis indicated that a history of smoking was an independent prognostic factor (hazard ratio, 1.36; P < .001).

CONCLUSIONS

More cigarette smoking, measured in pack-years, was associated with decreased survival after a diagnosis of stage IIIB/IV NSCLC. Trials assessing survival in patients with stage IIIB/IV NSCLC should report a detailed cigarette smoking history for all patients.

Lung adenocarcinoma: guiding EGFR-targeted therapy and beyond

Somatic mutations in certain tyrosine kinases have emerged as central 'drivers' of specific cancers and these mutant proteins are proving to be excellent substrates for targeted therapies. This is the case for mutant EGFR-dependent lung adenocarcinomas, where EGFR mutation testing is already being used to help guide treatment decisions. Here, we provide an overview of the biology of EGFR-targeted therapies and the clinical experience to date, the positive and negative predictors of response, pathologic correlates of EGFR-mutant status, testing methods to establish patient eligibility for these agents, and the basis for primary and secondary resistance.

EGFR mutations and EGFR tyrosine kinase inhibition in non-small cell lung cancer

OBJECTIVES

To discuss selected molecular targets and new clinical variables that can serve as both predictive and prognostic markers for outcome in patients with non-small cell lung cancer (NSCLC) treated with EGFR-TKIs.

DATA SOURCES

Research and journal articles.

CONCLUSION

In the near future, treatment for NSCLC will rely ever increasingly on molecular targets rather than empirically chosen cytotoxic chemotherapy for some patients. This will improve outcomes for patients with NSCLC.

IMPLICATIONS FOR NURSING PRACTICE

An understanding of the molecular targets and clinical variables that are predictive and prognostic of outcome in NSCLC will help nurses better care for these patients.

Molecular characteristics of bronchioloalveolar carcinoma and adenocarcinoma, bronchioloalveolar carcinoma subtype, predict response to erlotinib

PURPOSE

We conducted this phase II trial to determine the efficacy of erlotinib in patients with bronchioloalveolar carcinoma (BAC) and adenocarcinoma, BAC subtype, and to determine molecular characteristics associated with response.

PATIENTS AND METHODS

Patients (n = 101) with BAC (n = 12) or adenocarcinoma, BAC subtype (n = 89), were enrolled. All patients received erlotinib 150 mg daily. Epidermal growth factor receptor (EGFR) mutation, EGFR copy number, EGFR immunohistochemistry (IHC), and KRAS mutation status were analyzed in available tumors. The primary end point was response rate (RR).

RESULTS

Overall RR was 22% (95% CI, 14% to 31%). In patients with pure BAC, the RR and median survival were 20% and 4 months, as compared with 23% and 19 months in those with adenocarcinoma, BAC subtype. No patient (zero of 18; 95% CI, 0% to 19%) whose tumor harbored a KRAS mutation responded to erlotinib. Patients with EGFR mutations had an 83% RR (15 of 18; 95% CI, 65% to 94%) and 23-month median OS. On univariate analysis, EGFR mutation and copy number were associated with RR and PFS. EGFR IHC was not associated with RR or progression-free survival (PFS). After multivariate analysis, only EGFR mutation was associated with RR and PFS. No molecular factors were associated with overall survival.

CONCLUSION

Erlotinib is active in BAC and adenocarcinoma, mixed subtype, BAC. Testing for EGFR and KRAS mutations can predict RR and PFS after treatment with erlotinib in this histologically enriched subset of patients with non-small-cell lung cancer (NSCLC). These data suggest that histologic subtype and molecular characteristics should be reported in clinical trials in NSCLC using EGFR-directed therapy.

Mutations in the epidermal growth factor receptor gene and effects of EGFR-tyrosine kinase inhibitors on lung cancers

Epidermal growth factor receptor (EGFR) gene mutations are frequent in lung cancer arising in patients of Asian ethnicity, female sex, nonsmokers, and adenocarcinoma histology. About 70% of the patients with EGFR mutations respond to EGFR tyrosine kinase inhibitors (TKIs) including gefitinib and erlotinib, whereas only 10% of those without the mutations do so. Therefore, EGFR mutation is being recognized as one of the most reliable predictive factors for treatment using EGFR-TKIs. Another important issue in clinical practice is the fatal interstitial lung disease (ILD) that can develop in patients with gefitinib treatment, especially Asian patients. A nested case-control study recently conducted in Japan identified some risk factors that cause ILD, including age > or = 55 years, a history of smoking, preexisting ILD, poor performance status, short duration since diagnosis of lung cancer, reduced extent of normal lung on computed tomography, and concurrent cardiac disease. About half of the acquired resistance to EGFR-TKIs that almost always occurs during the course of treatment is caused by a secondary mutation at codon 790 (T790M). EGFR-TKIs are not universally effective for treating lung cancers but are effective in patients with particular genotypes. Therefore, patients who would benefit from EGFR-TKIs therapy should be concentrated in clinical trials. Based on this concept, Phase III clinical trials comparing gefitinib monotherapy with standard platinum-based chemotherapy are currently ongoing for patients with EGFR mutations and lung cancer.

Prospective assessment of discontinuation and reinitiation of erlotinib or gefitinib in patients with acquired resistance to erlotinib or gefitinib followed by the addition of everolimus

PURPOSE

Ten percent of U.S. patients with non-small cell lung cancer experience partial radiographic responses to erlotinib or gefitinib. Despite initial regressions, these patients develop acquired resistance to erlotinib or gefitinib. In these patients, we sought to assess changes in tumor metabolism and size after stopping and restarting erlotinib or gefitinib and to determine the effect of adding everolimus.

EXPERIMENTAL DESIGN

Patients with non-small cell lung cancer and acquired resistance to erlotinib or gefitinib were eligible. Patients had 18-fluoro-2-deoxy-d-glucose-positron emission tomography/computed tomography and computed tomography scans at baseline, 3 weeks after stopping erlotinib or gefitinib, and 3 weeks after restarting erlotinib or gefitinib. Three weeks after restarting erlotinib or gefitinib, everolimus was added to treatment.

RESULTS

Ten patients completed all four planned studies. Three weeks after stopping erlotinib or gefitinib, there was a median 18% increase in SUV(max) and 9% increase in tumor diameter. Three weeks after restarting erlotinib or gefitinib, there was a median 4% decrease in SUV(max) and 1% decrease in tumor diameter. No partial responses (0 of 10; 95% confidence interval, 0-31%) were seen with the addition of everolimus to erlotinib or gefitinib.

CONCLUSIONS

In patients who develop acquired resistance, stopping erlotinib or gefitinib results in symptomatic progression, increase in SUV(max), and increase in tumor size. Symptoms improve and SUV(max) decreases after restarting erlotinib or gefitinib, suggesting that some tumor cells remain sensitive to epidermal growth factor receptor blockade. No responses were observed with combined everolimus and erlotinib or gefitinib. We recommend a randomized trial to assess the value of continuing erlotinib or gefitinib after development of acquired resistance.

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.

Update on epidermal growth factor receptor mutations in non-small cell lung cancer

In 2004, several investigators reported that somatic mutations in the epidermal growth factor receptor gene were associated with clinical responses to erlotinib and gefitinib in patients with non-small cell lung cancer. Since then, multiple groups have examined the biological properties that such mutations confer as well as the clinical relevance of these mutations in patients with non-small cell lung cancer. Although a tremendous amount of knowledge has been gained in the past 2 years, there remain a number of important epidemiologic, biological, and clinical questions.