Epidermal growth factor receptor polymorphisms and clinical outcomes in non-small-cell lung cancer patients treated with gefitinib

Genetic Variants in the ABCB1 and ABCG2 Gene Drug Transporters Involved in Gefitinib-Associated Adverse Reaction: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis aimed to verify the association between the genetic variants of adenosine triphosphate (ATP)-binding cassette subfamily B member 1 (ABCB1) and ATP-binding cassette subfamily G member 2 (ABCG2) genes and the presence and severity of gefitinib-associated adverse reactions. We systematically searched PubMed, Virtual Health Library/Bireme, Scopus, Embase, and Web of Science databases for relevant studies published up to February 2024. In total, five studies were included in the review. Additionally, eight genetic variants related to ABCB1 (rs1045642, rs1128503, rs2032582, and rs1025836) and ABCG2 (rs2231142, rs2231137, rs2622604, and 15622C>T) genes were analyzed. Meta-analysis showed a significant association between the ABCB1 gene rs1045642 TT genotype and presence of diarrhea (OR = 5.41, 95% CI: 1.38-21.14, I2 = 0%), the ABCB1 gene rs1128503 TT genotype and CT + TT group and the presence of skin rash (OR = 4.37, 95% CI: 1.51-12.61, I2 = 0% and OR = 6.99, 95%CI: 1.61-30.30, I2= 0%, respectively), and the ABCG2 gene rs2231142 CC genotype and presence of diarrhea (OR = 3.87, 95% CI: 1.53-9.84, I2 = 39%). No ABCB1 or ABCG2 genes were positively associated with the severity of adverse reactions associated with gefitinib. In conclusion, this study showed that ABCB1 and ABCG2 variants are likely to exhibit clinical implications in predicting the presence of adverse reactions to gefitinib.

Analyses of P16INK4a gene promoter methylation relative to molecular, demographic and clinical parameters characteristics in non-small cell lung cancer patients: A pilot study

BACKGROUND

The aim of this study was to examine the methylation status of p16^INK4a promoter region in non small cell lung cancer (NSCLC) patients and their associations with single nucleotide polymorphisms (SNPs) of the epidermal growth factor receptor (EGFR) gene, as well as with demographic or clinical characteristics.

METHODS

Formalin-fixed and paraffin-embedded (FFPE) DNA samples extracted from 22 NSCLC patients were analyzed with methylation-specific polymerase chain reaction (PCR) method to obtain promoter methylation profile. The same cohort was genotyped for - 216G > T, -191 C > A, and 181,946 C > T EGFR SNPs.

RESULTS

There was a significant association between methylated p16^INK4a in patients prior therapy (p = 0.017) since a significantly higher frequency of methylated p16^INK4a was detected in these patients (40.9%) in comparison to frequency in patients after therapy (31.8%). Also, a higher frequency of methylated p16^INK4a was detected among patients with leucopenia (p = 0.056). No associations were observed between the methylation status of the p16^INK4a promoter region and EGFR SNPs or other clinical and demographic data in this cohort.

CONCLUSION

High frequency of methylation of the p16^INK4a gene promoter was observed in NSCLC patients prior therapy and with leucopenia that can indicate their significance related to advanced clinical stage.

Application of the conventional and novel methods in testing EGFR variants for NSCLC patients in the last 10 years through different regions: a systematic review

Variants in the epidermal growth factor receptor (EGFR) gene are recognized as predictors of therapy response and are correlated with progression-free and overall survival in non-small cell lung cancer (NSCLC) patients. Molecularly guided therapy needs precise and cost-effective molecular tests. This review focused primarily on screening or target methods for the EGFR variants detection with diagnostic and prognostic potential in the clinical research published papers. Concerning the inclusion and exclusion criteria, the search interval comprised available articles published from 2010 until 2020 in three electronic databases, ISI Web of Science, Pub Med, and Scopus. The analysis of eligible studies started with 5647 and obtained the final 987 full-text articles analyzed as clinical research. The regions comprised were Africa, America, Australia, Asia, Euro-Asia, Europe, or a consortium of different countries. All of the tested methods were applied prevalently in Asia. In clinical research, the polymerase chain reaction (PCR), followed by sequencing methods have been involved mostly over the years. The identified high-through output approaches evolved to improve the survival and quality of the NSCLC patient's life becoming more sensitive, specific, and cost-effective.

Pharmacogenetics for severe adverse drug reactions induced by molecular-targeted therapy

Molecular-targeted drugs specifically interfere with molecules that are frequently overexpressed or mutated in cancer cells. As such, these drugs are generally considered to precisely attack cancer cells, thereby inducing fewer adverse drug reactions (ADRs). However, molecular-targeted drugs can still cause characteristic ADRs that, although rarely severe, can be life-threatening. Therefore, it is becoming increasingly important to be able to predict which patients are at risk of developing ADRs after treatment with molecular-targeted therapy. The emerging field of pharmacogenetics aims to better distinguish the genetic variants associated with drug toxicity and efficacy to improve the selection of therapeutic strategies for each genetic profile. Here, we provide an overview of the current reports on the relationship between genetic variants and molecular-targeted drug-induced severe ADRs in oncology.

EGFR Polymorphism and Survival of NSCLC Patients Treated with TKIs: A Systematic Review and Meta-Analysis

Tyrosine kinase inhibitor- (TKI-) based therapy revolutionized the overall survival and the quality of life in non-small-cell lung cancer (NSCLC) patients that have epidermal growth factor receptor (EGFR) mutations. However, EGFR is a highly polymorphic and mutation-prone gene, with over 1200 single nucleotide polymorphisms (SNPs). Since the role of EFGR polymorphism on the treatment outcome is still a matter of debate, this research analyzed the available literature data, according to the PRISMA guidelines for meta-analyses. Research includes PubMed, Scopus, ISI Web of Science, and 14 of genome-wide association studies (GWAS) electronic databases in order to provide quantitative assessment of the association between ten investigated EGFR SNPs and the survival of NSCLC patients. The pooled HR and their 95% CI for OS and PFS for different EGFR polymorphisms using a random or fixed effect model based on the calculated heterogeneity between the studies was applied. The longest and the shortest median OSs were reported for the homozygous wild genotype and a variant allele carriers for rs712829 (-216G>T), respectively. Quantitative synthesis in our study shows that out of ten investigated EGFR SNPs (rs11543848, rs11568315, rs11977388, rs2075102, rs2227983, rs2293347, rs4947492, rs712829, rs712830, and rs7809028), only four, namely, rs712829 (-216G>T), rs11568315 (CA repeat), rs2293347 (D994D), and rs4947492, have been reported to affect the outcome of TKI-based NSCLC treatment. Of these, only -216G>T and variable CA repeat polymorphisms have been confirmed by meta-analysis of available data to significantly affect OS and PFS in gefitinib- or erlotinib-treated NSCLC patients.

The Association between Epidermal Growth Factor Receptor Single Nucleotide Polymorphisms and Radiochemotherapy Response in Cervical Cancer

Emerging data reveal that epidermal growth factor receptor (EGFR) single nucleotide polymorphisms (SNPs) can act as efficacy indicators for tumor treatment. Here, the association between EGFR R497K (rs11543848) and -216G/T (rs712829) SNPs and radiochemotherapy response in cervical cancer was investigated. EGFR R497K and -216G/T genotypes were analyzed by polymerase chain reaction-ligation detection reaction in 196 cervical cancer patients receiving radiotherapy alone, or in combination with chemotherapy. Compared with the 497G/G genotype, the A/A genotype significantly increased sensitivity to radiochemotherapy treatment (adjusted OR = 0.244, 95% CI = 0.087-0.680). Sensitivity to radiochemotherapy was not significantly different in carriers of the 'T' allele than that measured for the -216G/G genotype (adjusted OR = 2.412, 95% CI = 0.856-6.979). Additionally, the 497A/A genotype conferred a reduced risk of recurrence or metastasis than did the G/G genotype (adjusted OR = 0.248, 95% CI = 0.078-0.786, P < 0.05). Moreover, carriers of the 'T' allele did not have significantly modified risk of recurrence or metastasis compared with those with the -216G/G genotype (adjusted OR = 1.027, 95% CI = 0.324-3.253). Multivariate analysis revealed an association between clinical stage and treatment response (adjusted OR = 3.575, 95% CI = 1.662-7.692) and between age and the risk of recurrence or metastasis (adjusted OR = 0.319, 95% CI = 0.148-0.691). Our results show that, in patients with cervical cancer, the R497K polymorphism is correlated with treatment response and the risk of recurrence or metastasis. The R497K SNP might be a genetic marker for prediction of radiochemotherapy response and the risk of recurrence and/or metastasis in patients with cervical cancer.

Impact of single nucleotide polymorphisms on the efficacy and toxicity of EGFR tyrosine kinase inhibitors in advanced non-small cell lung cancer patients

EGFR tyrosine kinase inhibitors (EGFR-TKIs) are the treatment of choice for advanced-stage (IIIB-IV) NSCLC patients with mutations in EGFR. However, EGFR-TKIs clinical outcomes vary from person to person and these inter-individual differences may be due to genetic factors such as single nucleotide polymorphisms (SNPs). SNPs in genes involved in EGFR-TKIs pharmacodynamics, metabolism and mechanism of action have been demonstrated to be associated with response, survival and toxicity in advanced NSCLC patients treated with EGFR-TKIs. Here we review the influence of gene polymorphisms in the EGFR pathway on clinical outcome and toxicity to EGFR-TKIs in advanced NSCLC patients. The EGFR-216 polymorphism has reported a strong association between response and/or survival to EGFR-TKIs in Caucasian population. Similarly, the effect of EGFR-CA repeats polymorphisms on survival of advanced NSCLC patients treated with EGFR-TKIs have been confirmed both in Caucasian and Asian population. The influence on toxicity of the -216, -191, CA repeats, Arg497Lys and Asp994Asp polymorphisms in EGFR have also been confirmed. Polymorphisms in AKT (rs1130214 and rs1130233) and SMAD3 (rs6494633, rs11071938 and rs11632964) have been associated with survival in advanced NSCLC patients treated with EGFR-TKIs. However, data come from a limited number of studies and need to be confirmed. Finally, polymorphisms in genes coding proteins of the membrane transporters and cytochrome P450 enzymes have been less extensively investigated. There are few studies with small samples, which complicated the generalization of their role in EGFR-TKIs treatment.

Epidermal Growth Factor Receptor Gene in Non-Small-Cell Lung Cancer: The Importance of Promoter Polymorphism Investigation

Recently, epidermal growth factor receptor (EGFR) was a key molecule in investigation of lung cancer, and it was a target for a new therapeutic strategy, based on molecular analyses. In this review, we have summarized some issues considering the role of EGFR in lung cancer, its coding gene, and its promoter gene polymorphisms (SNPs) -216G/T and -191C/A in non-small-cell lung cancer (NSCLC). The position of the SNPs indicates their significant role in EGFR regulation. The accumulation of knowledge regarding SNPs lately suggests their significant and important role in the onset of carcinogenesis, the prediction of the onset of metastases, the response to therapy with TKI inhibitors, and the onset of toxic effects of the applied therapy. Based on this, we suggest further studies of the relationship of clinical significance to SNPs in patients with lung tumors.

Association of EGFR c.2073A>T Polymorphism with Decreased Risk of Diffusely Infiltrating Astrocytoma in a Brazilian Case-Control Study

Epidermal growth factor receptor (EGFR) gene overexpression has been implicated in the development of many types of tumors, including glioblastomas, the most frequent diffusely infiltrating astrocytomas. However, little is known about the influence of the polymorphisms of EGFR on EGFR production and/or activity, possibly modulating the susceptibility to astrocytomas. This study aimed to examine the association of two EGFR promoter polymorphisms (c-191C>A and c.-216G>T) and the c.2073A>T polymorphism located in exon 16 with susceptibility to astrocytomas, EGFR gene expression and survival in a case-control study of 193 astrocytoma patients and 200 cancer-free controls. We found that the variant TT genotype of the EGFR c.2073A>T polymorphism was associated with a significantly decreased risk of astrocytoma when compared with the AA genotype [sex- and age-adjusted odds ratio 0.51, 95% confidence interval 0.26–0.98]. No association of the two promoter EGFR polymorphisms (or combinations of these polymorphisms) and risk of astrocytomas, EGFR expression or survival was found. Our findings suggest that modulation of the EGFR c.2073A>T polymorphism could play a role in future therapeutic approaches to astrocytoma.

Erlotinib-Associated Rash in Advanced Non-Small Cell Lung Cancer: Relation to Clinicopathological Characteristics, Treatment Response, and Survival

Systematic treatment of advanced non-small cell lung cancer (NSCLC) includes targeted treatment with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). The development of skin rash and its intensity have been associated with EGFR TKI's efficacy. The main purpose of this study was to further investigate the potential value of erlotinib-associated rash as a predictor of prognosis and treatment response in a real-world cohort of patients with advanced NSCLC. The medical records of all NSCLC patients treated with erlotinib at the Oncology Unit of GPP, Sotiria Athens General Hospital between January 1, 2014 and August 31, 2016 were retrospectively reviewed. Seventy-nine patient medical records fulfilled the criteria and were included in the study. Development of erlotinib-associated rash was correlated with clinicopathological characteristics of patients, treatment response, and overall survival (OS) using univariate and multivariate Cox regression analysis. The number of patients with rash was greater in the responders group (90% vs. 46.4%, p = 0.015). In univariate analysis, there was a statistically significant association between rash development and time to progression (TTP) [HR: 0.32 (0.17-0.57), p < 0.001]. With multivariate Cox regression analysis, it was found that PS ≥ 2 (HR: 2.01, 95% CI: 1.12-3.60, p = 0.018) and rash (HR: 0.34, 95% CI: 0.18-0.63, p = 0.001) were independently associated with TTP and also that the duration of treatment with erlotinib (HR: 0.58, 95% CI: 0.42-0.80, p = 0.001) and rash (HR: 0.10, 95% CI: 0.20-0.48, p = 0.004) was an independent predictor of survival. Our results suggest that erlotinib-associated rash may represent a clinically valuable biomarker for the prediction of treatment response and OS in patients with advanced NSCLC.

Biomarker analysis of the phase 3 TORCH trial for first line erlotinib versus chemotherapy in advanced non-small cell lung cancer patients

Background

The TORCH phase III trial compared the efficacy of first-line erlotinib followed by chemotherapy at progression (experimental arm) with the reverse sequence (standard arm) in unselected advanced non-small cell lung cancer (NSCLC) patients. Here we report biomarker analyses.

Methods

EGFR and KRAS mutation, expression of EGFR family members and of cMET and PTEN and EGFR and ABCG2 germline polymorphisms were tested on tumor tissue or blood samples to either confirm previously proposed predictive role or describe it in an explorative setting. Progression-free survival (PFS) was the primary end-point, overall survival, response rate and side effects (diarrhoea and skin toxicity) were secondary end-points. Interactions between biomarkers and treatment were studied with multivariable models (either Cox model or logistic regression). Statistical analyses accounted for multiple comparisons.

Results

At least one biomarker was assessed in 324 out of 760 patients in the TORCH study. EGFR mutation was more common in female (P = 0.0001), East Asians (P < 0.0001) and never smoker (P < 0.0001) patients; low MET protein expression by IHC (H-score <200) was more frequent in squamous (P < 0.00009) and ABCG2 C/A or A/A polymorphism was more frequent among East-Asian patients (P = 0.0003). A significant interaction was found for EGFR mutation in PFS and response rate analyses while no predictive effect on OS was found for any biomarker. No biomarker tested was prognostic for PFS and OS. No polymorphism was significantly associated with skin toxicity or diarrhea.

Conclusion

In the present study, beyond the known role of EGFR mutation, no other biomarker has predictive or prognostic role.

Skin problems and EGFR-tyrosine kinase inhibitor

Epidermal growth factor receptor inhibition is a good target for the treatment of lung, colon, pancreatic and head and neck cancers. Epidermal growth factor receptor-tyrosine kinase inhibitor was first approved for the treatment of advanced lung cancer in 2002. Epidermal growth factor receptor-tyrosine kinase inhibitor plays an essential role in the treatment of cancer, especially for patients harbouring epidermal growth factor receptor activating mutation. Hence, skin toxicity is the most concerning issue for the epidermal growth factor receptor-tyrosine kinase inhibitor treatment. Skin toxicity is bothersome and sometimes affects the quality of life and treatment compliance. Thus, it is important for physicians to understand the background and how to manage epidermal growth factor receptor-tyrosine kinase inhibitor-associated skin toxicity. Here, the author reviewed the mechanism and upfront preventive and reactive treatments for epidermal growth factor receptor inhibitor-associated skin toxicities.

Genetic Association of Curative and Adverse Reactions to Tyrosine Kinase Inhibitors in Chinese advanced Non-Small Cell Lung Cancer patients

Epidermal growth factor receptor (EGFR) Tyrosine kinase inhibitor (TKI) is an effective targeted therapy for advanced non-small cell lung cancer (NSCLC) but also causes adverse drug reactions (ADRs) e.g., skin rash and diarrhea. SNPs in the EGFR signal pathway, drug metabolism/ transport pathways and miRNA might contribute to the interpersonal difference in ADRs but biomarkers for therapeutic responses and ADRs to TKIs in Chinese population are yet to be fully investigated. We recruited 226 Chinese advanced NSCLC patients who received TKIs erlotinib, gefitinib and icotinib hydrochloride and systematically studied the genetic factors associated with therapeutic responses and ADRs. Rs884225 (T > C) in EGFR 3′ UTR was significantly associated with lower risk of ADRs to erlotinib (p value = 0.0010, adjusted p value = 0.042). A multivariant interaction four-SNP model (rs884225 in EGFR 3′UTR, rs7787082 in ABCB1 intron, rs38845 in MET intron and rs3803300 in AKT1 5′UTR) was associated with ADRs in general and the more specific drug induced skin injury. The SNPs associated with both therapeutic responses and ADRs indicates they might share a common genetic basis. Our study provided potential biomarkers and clues for further research of biomarkers for therapeutic responses and ADRs in Chinese NSCLC patients.

Genetic polymorphism in the epidermal growth factor receptor gene predicts outcome in advanced non-small cell lung cancer patients treated with erlotinib

OBJECTIVES

Epidermal growth factor receptor (EGFR) mutations are important predictors of treatment response to tyrosine kinase inhibitors (TKIs) in patients with non-small cell lung cancer (NSCLC). However, some patients with mutations do not respond and some patients without mutations show response. We therefore need additional biomarkers to improve the selection of these patients for treatment. A promising candidate could be germline genetic variations in the EGFR gene that can alter protein expression or function and may influence the response to TKIs. Thus, the aim of this study was to evaluate the predictive role of genetic variations in the EGFR gene in advanced NSCLC patients treated with a TKI.

MATERIALS AND METHODS

Genotypes for -216G>T, -191C>A and 181946C>T in the EGFR gene were retrospectively evaluated by DNA sequencing and allele-specific PCR analysis in 331 Caucasian patients with advanced NSCLC. Genotypes were correlated with clinical characteristics, toxicity and outcome. A multivariate analysis was performed using Cox proportional hazards model while adjusting for clinically relevant factors including EGFR mutation status.

RESULTS

181946CT or TT genotypes showed an association with clinical outcome compared with patients with the 181946CC genotype (disease control rate (DCR), 68% versus 52%; P=0.049; progression-free survival (PFS), adjusted hazard ratio (HR)=0.74 (95% confidence interval (CI): 0.55-0.99); overall survival (OS), adjusted HR=0.73 (95% CI: 0.54-0.97)). Subgroup analysis demonstrated that the association may be most relevant in EGFR mutation-positive patients (PFS, adjusted HR=0.43 (95% CI: 0.22-0.82); OS, adjusted HR=0.47 (95% CI: 0.24-0.93)).

CONCLUSION

The 181946C>T polymorphisms in the EGFR gene seems to be a potential predictor of higher DCR, longer PFS and OS in advanced NSCLC patients treated with erlotinib, especially in EGFR mutation-positive patients. Thus, this SNP may be a new potential tool for selection of patients for treatment. Prospective randomized studies are wanted to confirm our data.

High-throughput screening identified inherited genetic variations in the EGFR pathway contributing to skin toxicity of EGFR inhibitors

Aim: To identify genomic variants in the EGFR pathway and in cytokines predisposing to skin toxicity from EGFR inhibitors. Patients & methods: In 126 patients with cancer and EGFR inhibitor therapy skin toxicity was quantified and EGFR and inflammatory pathway genes were analyzed by deep sequencing. Results: We found 1437 SNPs in the 382-kb target region. Three SNPs in EGFR intron 1 were found exclusively in patients without skin rash. Another EGFR intron 23 SNP was associated with skin rash, overall survival and IL8 plasma concentrations. Moreover, carriers of the PIK3R1 326I variant were predisposed to skin rash and better survival. Conclusion: Comprehensive pathway-based resequencing revealed some new but only moderately strong genomic predictors of skin toxicity.

EGF and EGFR genetic polymorphisms predict prognosis in locally advanced pharyngolaryngeal squamous cell carcinoma patients receiving postoperative concurrent chemoradiotherapy

Background

Epidermal growth factor (EGF) and its receptor (EGFR) are part of an important signaling pathway that is involved in the pathogenesis of squamous cell carcinoma of the head and neck (SCCHN). We hypothesized that EGF/EGFR genetic polymorphisms might have a prognostic impact on disease-free survival and overall survival (OS) in locally advanced SCCHN.

Materials and methods

The patient group included a consecutive cohort of 180 patients with locally advanced SCCHN who underwent postoperative concurrent chemoradiotherapy between 2002 and 2010. DNA from formalin-fixed, paraffin-embedded tumor tissues was genotyped for the single nucleotide polymorphism (SNP) of EGF A61G A>G, EGFR R521K G>A and G-216T. The log-rank test was applied to evaluate the impact of SNPs on the outcomes. Survival was estimated using the Kaplan–Meier statistical method.

Results

We demonstrated that EGF/EGFR SNPs might predict prognosis in patients with primary pharyngolaryngeal tumors, but not in those with oral cavity tumors. In pharyngolaryngeal tumor subgroup, EGF61 G/G genotype led to worse 5 year OS rate when compared to G/A or A/A genotypes (13.3% versus 34.3% versus 50.0%, P=0.017). The 5 year OS of patients with EGFR R521K G/G (11.1%) and G/A (15.9%) were lower than the A/A (62.5%) genotype (P=0.054). Patients carrying one or two unfavorable alleles had worse 5 year OS than those without unfavorable allele (not available versus 20% versus 71.4%, P=0.002). Multivariate analysis revealed that the highest risk of death was associated with the coexistence of two unfavorable genotypes (hazard ratio 25.7, 95% confidence interval =3.4–193.4; P=0.002).

Conclusion

In this study, we were able to demonstrate that the EGF A61G and EGFR R521K genetic polymorphisms might be important prognostic factors in patients with locally advanced primary pharyngolaryngeal squamous cell carcinoma who underwent postoperative concurrent chemoradiotherapy.

A Meta-Analysis on the Relations between EGFR R521K Polymorphism and Risk of Cancer

The EGFR R521K polymorphism has been shown to reduce the activity of EGFR; however, the association between EGFR R521K polymorphism and the risk of cancer remains inconclusive; therefore we performed a meta-analysis to evaluate the relationship between EGFR R521K polymorphism and susceptibility to cancer. Our results suggest that the EGFR R521K polymorphism is not associated with risk of cancer, but the different chemosensitivity to anticancer drugs may need further investigation.

EGFR CA repeat polymorphism predict clinical outcome in EGFR mutation positive NSCLC patients treated with erlotinib

OBJECTIVES

Somatic mutations in the epidermal growth factor receptor (EGFR) are predictors of efficacy for treatment with the EGFR tyrosine kinase inhibitor erlotinib in non-small cell lung cancer (NSCLC). A CA repeat polymorphism in intron 1 of the EGFR gene influences the transcription of the EGFR gene. This study evaluates the association between the CA repeat polymorphism and outcome in NSCLC patients treated with erlotinib.

MATERIALS AND METHODS

Number of CA repeats in the EGFR gene was evaluated with PCR-fragment length analysis by capillary electrophoresis in 432 advanced NSCLC patients treated with erlotinib irrespective of EGFR mutation status. Patients were dichotomized into harboring short allele (CA≤16 in any allele) or long alleles (CA>16 in both alleles). Number of repeats was correlated with clinical characteristic and outcome. A subgroup analysis was performed based on the somatic EGFR mutation status.

RESULTS

In EGFR mutation positive patients (N=62) we demonstrate a significantly higher median progression free survival (HR=0.39 (0.22-0.70); p=0.002) and overall survival (HR=0.43 (0.23-0.78); p=0.006) in patients also harboring a short CA repeat length vs. a long (median follow-up time of 52.2 months). The result remained highly significant in a multivariate Cox proportional hazards model. This correlation was not seen in EGFR mutation negative patients.

CONCLUSION

Our study demonstrate that in EGFR mutation positive NSCLC patients treated with erlotinib a low number of CA repeats in intron 1 of the EGFR gene is a predictor for both longer progression free survival and overall survival.

Toxicity of targeted therapy: Implications for response and impact of genetic polymorphisms

Targeted therapies have unique toxicity profiles. Common adverse events include rash, diarrhea, hypertension, hypothyroidism, proteinuria, depigmentation, and hepatotoxicity. Some of these toxicities are caused by on-target, mechanism-associated effects, which can be stratified as to whether or not the targets are relevant to response. Other toxicities are off-target and may be caused by the class of agent, e.g. antibody vs small molecule tyrosine kinase inhibitor, or by immune reactions or toxic metabolites. Both on- and off-target toxicities may be due to higher drug concentrations or altered end-organ sensitivity, which in turn can be a consequence of genetic polymorphisms controlling metabolism or tissue responsiveness. On-target toxicities are important to identify as some correlate with response and, hence, amelioration of these side effects is preferable to dose reduction or stopping drug. Toxicities secondary to relevant target impact may be recognized when distinct types of agents, such as antibodies and small molecule kinase inhibitors, with the same target have a similar side effect. For example, both bevacizumab and vascular endothelial growth factor receptor (VEGFR) kinase inhibitors cause hypertension; both epidermal growth factor receptor (EGFR) antibodies and kinase inhibitors cause rash; and these toxicities correlate with response. Herein we review common targeted agent-related toxicities, relevant genetic polymorphisms, and implications for response and patient management.

Epidermal growth factor receptor gene polymorphisms are associated with prognostic features of breast cancer

BACKGROUND

The epidermal growth factor receptor (EGFR) is differently expressed in breast cancer, and its presence may favor cancer progression. We hypothesized that two EGFR functional polymorphisms, a (CA)n repeat in intron 1, and a single nucleotide polymorphism, R497K, may affect EGFR expression and breast cancer clinical profile.

METHODS

The study population consisted of 508 Brazilian women with unilateral breast cancer, and no distant metastases. Patients were genotyped for the (CA)n and R497K polymorphisms, and the associations between (CA)n polymorphism and EGFR transcript levels (n = 129), or between either polymorphism and histopathological features (n = 505) were evaluated. The REMARK criteria of tumor marker evaluation were followed.

RESULTS

(CA)n lengths ranged from 14 to 24 repeats, comprehending 11 alleles and 37 genotypes. The most frequent allele was (CA)16 (0.43; 95% CI = 0.40-0.46), which was set as the cut-off length to define the Short allele. Variant (CA)n genotypes had no significant effect in tumoral EGFR mRNA levels, but patients with two (CA)n Long alleles showed lower chances of being negative for progesterone receptor (ORadjusted = 0.42; 95% CI = 0.19-0.91). The evaluation of R497K polymorphism indicated a frequency of 0.21 (95% CI = 0.19 - 0.24) for the variant (Lys) allele. Patients with variant R497K genotypes presented lower proportion of worse lymph node status (pN2 or pN3) when compared to the reference genotype Arg/Arg (ORadjusted = 0.32; 95% CI = 0.17-0.59), which resulted in lower tumor staging (ORadjusted = 0.34; 95% CI = 0.19-0.63), and lower estimated recurrence risk (OR = 0.50; 95% CI = 0.30-0.81). The combined presence of both EGFR polymorphisms (Lys allele of R497K and Long/Long (CA)n) resulted in lower TNM status (ORadjusted = 0.22; 95% CI = 0.07-0.75) and lower ERR (OR = 0.25; 95% CI = 0.09-0.71). When tumors were stratified according to biological classification, the favorable effects of variant EGFR polymorphisms were preserved for luminal A tumors, but not for other subtypes.

CONCLUSIONS

The data suggest that the presence of the variant forms of EGFR polymorphisms may lead to better prognosis in breast cancer, especially in patients with luminal A tumors.

Optimization of PCR conditions for amplification of GC-Rich EGFR promoter sequence

BACKGROUND

Polymerase chain reaction (PCR) is an extremely sensitive method that often demands optimization, especially when difficult templates need to be amplified. The aim of the present study was to optimize the PCR conditions for amplification of the epidermal growth factor receptor (EGFR) promoter sequence featuring an extremely high guanine-cytosine (GC) content in order to detect single nucleotide polymorphisms -216G>T and -191C>A.

METHODS

Genomic DNA used for amplification was extracted from formalin-fixed paraffin-embedded lung tumor tissue and PCR products were detected by agarose gel electrophoresis.

RESULTS

Results showed that addition of 5% dimethyl sulfoxide (DMSO), as well as DNA concentration in PCR reaction of at least 2 μg/ml, were necessary for successful amplification. Due to high GC content, optimal annealing temperature was 7°C higher than calculated, while adequate MgCl2 concentration ranged from 1.5 to 2.0 mM.

CONCLUSION

In conclusion, EGFR promoter region is a difficult PCR target, but it could be amplified after optimization of MgCl2 concentration and annealing temperature in the presence of DMSO and the DNA template of acceptable concentration.

Tyrosine kinase inhibitors: their on-target toxicities as potential indicators of efficacy

Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of certain forms of cancers, raising hopes for many patients with otherwise unresponsive tumours. While these agents are generally well tolerated, clinical experience with them has highlighted their unexpected association with serious toxic effects on various organs such as the heart, lungs, liver, kidneys, thyroid, skin, blood coagulation, gastrointestinal tract and nervous system. Many of these toxic effects result from downstream inhibition of vascular endothelial growth factor or epidermal growth factor signalling in cells of normal organs. Many of these undesirable effects such as hypertension, hypothyroidism, skin reactions and possibly proteinuria are on-target effects. Since tyrosine kinases are widely distributed with specific functional roles in different organs, this association is not too surprising. Various studies suggest that the development of these on-target effects indicates clinically desirable and effective inhibition of the corresponding ligand-mediated receptor linked with oncogenesis. This is reflected as improved efficacy in the subgroup of patients who develop these on-target adverse effects compared with those who do not. Inevitably, issues arise with respect to the regulatory assessment of efficacy and risk/benefit of the TKIs as well as the clinical approach to managing patients who develop these effects. Routine subgroup analysis of efficacy data from clinical trials (patients with and without on-target toxicity) may enable more effective clinical use of TKIs since (i) discontinuing or reducing the dose of the TKI has a negative impact if the tumour is TKI-responsive; and (ii) it is usually possible to manage these undesirable on-target effects with conventional clinical approaches. Prospective studies are needed to investigate this proposition further.

-216G/T (rs712829), a functional variant of the EGFR promoter, is associated with the pleural metastasis of lung adenocarcinoma

Numerous mutations and variants in the epidermal growth factor receptor (EGFR) gene have been demonstrated to be associated with the occurrence, metastasis and prognosis of various types of tumors, including lung cancer. Thus, the present study aimed to investigate whether -216G/T (rs712829), a functional polymorphism of the EGFR promoter that is able to induce EGFR activation and overexpression, is associated with the pleural metastasis of lung adenocarcinoma. The study subjects were comprised of 326 patients with primary lung adenocarcinoma and 312 matched cases with pleural metastasis. The -216G/T genotypes were determined in all subjects by PCR amplification and direct DNA sequencing, and EGFR expression was also evaluated by immunohistochemical staining in the primary tumor tissues with various -216G/T genotype backgrounds. The results showed that the frequencies of allele T and genotypes G/T and T/T in the pleural metastasis group were significantly higher compared with those in the non-metastasis group, with adjusted ORs of 1.46 (95% CI, 1.015–1.963) for G/T and 1.97 (95% CI, 1.051–3.152) for T/T. Furthermore, the expression of the EGFR protein was higher in the primary lung adenocarcinoma tissues with -216T/T and -216G/T compared with those with -216G/G (P<0.05). These results collectively indicate that the -216G/T polymorphism in the EGFR promoter is associated with the risk of the pleural metastasis of lung adenocarcinoma and that this effect may be associated with -216G/T-induced overexpression of the EGFR protein.

[Effects of EGFR gene polymorphisms on efficacy and prognosis in advanced non-small cell lung cancer treated with EGFR-TKIs]

表皮生长因子受体酪氨酸激酶抑制剂（epidermal growth factor receptor tyrosine kinase inhibitors, EGFR-TKIs）在晚期非小细胞肺癌患者（non-small cell lung cancer, NSCLC）中的应用越来越广泛，但患者的疗效存在明显差异。目前主要是根据EGFR基因突变来选择患者，然而，其检测常受到肿瘤组织来源困难、技术复杂、费用高等因素限制。因此，临床亟待寻求其他生物学标记物来预测EGFR-TKIs疗效。近来有诸多研究发现EGFR基因多态性与晚期NSCLC患者EGFR-TKIs疗效及预后也存在相关性，现将其研究进展作一综述。

Role of EGFR SNPs in survival of advanced lung adenocarcinoma patients treated with Gefitinib

AIM

As a novel molecularly targeting agent for non-small-cell lung cancer (NSCLC), Gefitinib can block its tyrosine kinase activity of the epidermal growth factor receptor (EGFR). Genetic variations in EGFR may affect its protein function or expression and lead to diverse outcomes in NSCLC patients after Gefitinib therapy. Therefore, this prospective study examined whether EGFR single nucleotide polymorphisms (SNPs) are associated with different survival time in advanced lung adenocarcinoma patients treated with Gefitinib.

METHODS

One hundred and twenty-eight patients with stage IIIB or IV lung adenocarcinoma receiving Gefitinib target therapy between 2008 and 2010 were recruited in this study. Six EGFR haplotype-tagging SNPs were genotyped by the Sequenom MassArray system. Survival by different genotypes was compared using Kaplan-Meier methods. Cox proportional hazards models were applied to estimate the effect of prognostic factors on overall survival (OS) and progression-free survival (PFS).

RESULTS

After the median 16.6 months of follow-up, the unfavorable EGFR rs2293347AA or GA genotype was significantly correlated with shorter OS (AA vs. GG: 2.0 vs. 21.0 months; hazard ratio (HR)=2.44, 95% confidence interval (CI)=1.06-5.56; P=0.036; GA vs. GG: 15.0 vs. 21.0 months; HR=1.75, 95%CI=1.08-2.86, P=0.025) compared with the favorable rs2293347GG genotype. The prognostic significance of EGFR rs4947492 polymorphism on OS also existed (GG carriers vs. AA carriers: median OS=24.6 vs. 14.9 months, HR=0.29, 95%CI=0.10-0.83, P=0.021). No significant associations were found among other EGFR SNPs and survival.

CONCLUSION

EGFR rs2293347 and rs4947492 SNPs might be potential predictive markers of OS in advanced lung adenocarcinoma patients treated with Gefitinib.

Cancer genes in lung cancer: racial disparities: are there any?

Cancer is now known as a disease of genomic alterations. Mutational analysis and genomics profiling in recent years have advanced the field of lung cancer genetics/genomics significantly. It is becoming more accepted now that the identification of genomic alterations in lung cancer can impact therapeutics, especially when the alterations represent "oncogenic drivers" in the processes of tumorigenesis and progression. In this review, we will highlight the key driver oncogenic gene mutations and fusions identified in lung cancer. The review will summarize and report the available demographic and clinicopathological data as well as molecular details behind various lung cancer gene alterations in the context of race. We hope to shed some light into the disparities in the incidence of various genetic mutations among lung cancer patients of different racial backgrounds. As molecularly targeted therapy continues to advance in lung cancer, racial differences in specific genetic/genomic alterations can have an important impact in the choices of therapeutics and in our understanding of the drug sensitivity/resistance profile. The most relevant genes in lung cancer described in this review include the following: EGFR, KRAS, MET, LKB1, BRAF, PIK3CA, ALK, RET, and ROS1. Commonly identified genetic/genomic alterations such as missense or nonsense mutations, small insertions or deletions, alternative splicing, and chromosomal fusion rearrangements were discussed. Relevance in current targeted therapeutic drugs was mentioned when appropriate. We also highlighted various targeted therapeutics that are currently under clinical development, such as the MET inhibitors and antibodies. With the advent of next-generation sequencing, the landscape of genomic alterations in lung cancer is expected to be much transformed and detailed in upcoming years. These genomic landscape differences in the context of racial disparities should be emphasized both in tumorigenesis and in drug sensitivity/resistance. It is hoped that such effort will help to diminish racial disparities in lung cancer outcome in the future.

EGF receptor-targeted therapy in non-small-cell lung cancer: role of germline polymorphisms in outcome and toxicity

Conventional chemotherapeutic regimens have limited impact against most solid tumors and deal with significant toxicity. Over the last 10 years, novel anticancer treatments targeting specific molecules or genes involved in cancer progression have been developed to improve outcome and reduce side effects. In particular, the tyrosine kinase inhibitors gefitinib and erlotinib have been approved for the treatment of non-small-cell lung cancer. Their clinical activity has been related to different clinical and biological parameters, such as EGFR-activating mutations. However, not all clinical outcomes, including tolerability, are explained, and the identification/validation of novel biomarkers is a viable area of research. Germline polymorphisms can be easily assessed in blood samples, and candidate polymorphisms in EGFR and ABCG2 have been correlated with outcome and toxicity in non-small-cell lung cancer patients treated with gefitinib or erlotinib. However, differences in study population and design resulted in several controversial findings, while the prognostic versus predictive role of the polymorphisms still needs to be validated within larger prospective studies. More studies on the relationship of the genotype with drug pharmacokinetics and mechanism of action are also warranted. These future studies, as well as further development and application of novel technologies to decipher genetic alterations, might contribute to the validation of selected polymorphisms as molecular markers predictive of drug activity and help in the selection of tyrosine kinase inhibitors best suited to the individual patient.

Can knowledge of germline markers of toxicity optimize dosing and efficacy of cancer therapy?

The systemic treatment of cancer with traditional cytotoxic chemotherapeutic agents and more targeted agents is often complicated by the onset of adverse drug reactions. Pharmacogenetic prediction of adverse drug reactions might have consequences for dosing and efficacy. This review discusses relevant examples where the germline variant-toxicity relationship has been validated as an initial step in developing clinically useful pharmacogenetic markers and provides examples where germline variants have influenced dosing strategies and/or survival or other outcomes of efficacy. This review will also provide insight into the reasons why more pharmacogenetic markers have not been routinely integrated into clinical practice.

Polymorphisms in intron 1 of the EGFR gene in non-small cell lung cancer patients

The epidermal growth factor receptor (EGFR) gene is highly polymorphic and its expression and activity may be affected by various polymorphisms. There have been several studies examining associations between EGFR polymorphisms and clinical outcome of lung cancer therapy; however, the underlying mechanism is largely unknown. The present study investigated EGFR polymorphism status and its correlation with clinicopathological features in Japanese non-small cell lung cancer (NSCLC) patients. We investigated 5 polymorphisms in the EGFR gene (−216G/T, −191C/A, 8227G/A, D994D and R497K) in 274 surgically-treated NSCLC patients. TaqMan single nucleotide polymorphism (SNP) genotyping assays and a PCR-based assay were used to analyze these polymorphisms. In our cohort of patients we did not find any evidence of the −191C/A polymorphism. Our results showed that the patients with the 8227GA or AA type in intron 1 had a significantly better prognosis with the anti-EGFR therapy than the patients with the GG type (p=0.0448) in terms of recurrence of lung cancer. No significant association was observed between 3 other SNPs (−216G/T, D994D and R497K) and clinicopathological features. The EGFR 8227G/A polymorphism in intron 1 may be associated with clinical outcome in NSCLC patients treated with EGFR tyrosine kinase inhibitors.

Functional drug-gene interactions in lung cancer

Despite the dawn of the genomic information era, the challenges of cancer treatment remain formidable. Particularly for the most prevalent cancer types, including lung cancer, successful treatment of metastatic disease is rare and escalating costs for modern targeted drugs place an increasing strain on healthcare systems. Although powerful diagnostic tools to characterize individual tumor samples in great molecular detail are becoming rapidly available, the transformation of this information into therapy provides a major challenge. A fundamental difficulty is the molecular complexity of cancer cells that often causes drug resistance, but can also render tumors exquisitely sensitive to targeted agents. By using lung cancer as an example, we outline the principles that govern drug sensitivity and resistance from a genetic perspective and discuss how in vitro chemical-genetic screens can impact on patient stratification in the clinic.

Prognostic and predictive biomarkers for epidermal growth factor receptor-targeted therapy in colorectal cancer: beyond KRAS mutations

The advent of the epidermal growth factor receptor (EGFR)-targeted monoclonal antibodies (mAbs), cetuximab and panitumumab has expanded the range of treatment options for metastatic colorectal cancer (CRC). Despite these agents have paved the way to individualized therapy, our understanding why some patients respond to treatment whereas others do not remain poor. The realization that detection of positive EGFR expression by IHC does not reliably predict clinical outcome of EGFR-targeted treatment has led to an intense search for alternative predictive biomarkers. Data derived from multiple phase III trials have indicated that KRAS mutations can be considered a highly specific negative biomarker of benefit to anti-EGFR mAbs. Oncologists are now facing emerging issues in the treatment of metastatic CRC, including the identification of additional genetic determinants of primary resistance to EGFR-targeted therapy for further improving selection of patients, the explanation of rare cases of patients carrying KRAS-mutated tumours who have been reported to respond to cetuximab and panitumumab and the discovery of mechanisms of secondary resistance to EGFR-targeted therapy. Current data suggest that, together with KRAS mutations, the evaluation of EGFR gene copy number (GCN), BRAF, NRAS, PIK3CA mutations or loss of PTEN expression could also be useful for selecting patients with reduced chance to benefit from anti-EGFR mAbs. This review aims to provide an updated of the most recent data on predictive and prognostic biomarkers within the EGFR pathway, the challenges this emerging field presents and the future role of these molecular markers in CRC treatment.

Single nucleotide polymorphisms as susceptibility, prognostic, and therapeutic markers of nonsmall cell lung cancer

Lung cancer is a major public health problem throughout the world. Among the most frequent cancer types (prostate, breast, colorectal, stomach, lung), lung cancer is the leading cause of cancer-related deaths worldwide. Among the two major subtypes of small cell lung cancer and nonsmall cell lung cancer (NSCLC), 85% of tumors belong to the NSCLC histological types. Small cell lung cancer is associated with the shortest survival time. Although tobacco smoking has been recognized as the major risk factor for lung cancer, there is a great interindividual and interethnic difference in risk of developing lung cancer given exposure to similar environmental and lifestyle factors. This may indicate that in addition to chemical and environmental factors, genetic variations in the genome may contribute to risk modification. A common type of genetic variation in the genome, known as single nucleotide polymorphism, has been found to be associated with susceptibility to lung cancer. Interestingly, many of these polymorphisms are found in the genes that regulate major pathways of carcinogen metabolism (cytochrome P450 genes), detoxification (glutathione S-transferases), adduct removal (DNA repair genes), cell growth/apoptosis (TP53/MDM2), the immune system (cytokines/chemokines), and membrane receptors (nicotinic acetylcholine and dopaminergic receptors). Some of these polymorphisms have been shown to alter the level of mRNA, and protein structure and function. In addition to being susceptibility markers, several of these polymorphisms are emerging to be important for response to chemotherapy/radiotherapy and survival of patients. Therefore, it is hypothesized that single nucleotide polymorphisms will be valuable genetic markers in individual-based prognosis and therapy in future. Here we will review some of the most important single nucleotide polymorphisms in the metabolic pathways that may modulate susceptibility, prognosis, and therapy in NSCLC.

Toxicity as a biomarker of efficacy of molecular targeted therapies: focus on EGFR and VEGF inhibiting anticancer drugs

In addition to being present in tumor cells, many targets of signal transduction inhibitors are also found in normal tissue. Side effects attributable to the mechanism of action of molecular targeted agents thus represent "on-target" modulation in normal tissues. These mechanism-based toxicities can be pharmacodynamic effects of pathway inhibition and, in tumors depending on the inhibited pathway for proliferation, might be biomarkers of efficacy. The development of rash with tyrosine kinase inhibitors or monoclonal antibodies targeting the epidermal growth factor receptor is associated with superior outcomes in lung, head and neck, colorectal, and pancreatic cancer studies. Correlated with superior efficacy in retrospective analyses of large studies in advanced colorectal, breast, and renal cell carcinoma, arterial hypertension as an adverse event of antiangiogenic agents may also be a marker of effective target inhibition. An association between hypothyroidism and the activity of multitargeted tyrosine kinase inhibitors has been identified in renal cell carcinoma patients. Tumor growth addiction to the specific pathway that is effectively targeted may be the link between a mechanism-based toxicity and efficacy. The biological basis for this correlation can be pharmacological, with higher drug exposure being associated with greater toxicity and antitumor activity, and can also be genetic, because single nucleotide polymorphisms play an important role in drug pharmacokinetic and pharmacodynamic processes. Investigators have proposed that interpatient differences and associated toxicities can be exploited for dose selection and titration, and clinical trials are currently exploring intrapatient "dosing-to-toxicity" strategies. Ultimately, the predictive value of a side effect of molecular targeted therapies requires validation in prospective trials.

Genetic determinants of anticancer drug activity: towards a global approach to personalized cancer medicine

While current trials of anticancer agents serve to provide a population-based validation of therapeutic activity, clinical success is typically restricted to tumors of select molecular subtype. Recent insights have yielded a growing catalogue of germline and tumor-based aberrations that can predetermine whether a patient will achieve clinical benefit from a drug or not. Thus, in order to realize the true potential of anticancer agents, we need to define the molecular contexts under which they will prove both efficacious and safe. In this article, we provide an overview of such molecular determinants and introduce the concept of 'cancer patient profiling' - the process and science of defining the optimal therapy for a given patient through the generation and analysis of system-wide molecular information.

Biomarkers of clinical benefit for anti-epidermal growth factor receptor agents in patients with non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC) remains by far the major cause of cancer-related death in the Western world in both men and women. The majority of patients will be diagnosed with metastatic disease, and chemotherapy doublets remain the cornerstone of treatment for these patients. However, chemotherapy has a minimal impact on long-term survival and prognosis remains poor for these patients. Further improvement in treatment is likely to require incorporation of novel targeted therapies. Among these agents, inhibitors of the epidermal growth factor receptor (EGFR) have demonstrated significant activity in the first-, second- or third-line treatment of NSCLC. The purpose of current paper is to present the evidence for using several proposed molecular biomarkers as a tool for selection of NSCLC patients for anti-EGFR treatment. According to current data, EGFR mutation status appears to be the strongest predictor for the selection of NSCLC patients to first-line treatment with EGFR tyrosine kinase inhibitors vs chemotherapy. Use of other biomarkers remains investigational.

CYP1A1*2A polymorphism as a predictor of clinical outcome in advanced lung cancer patients treated with EGFR-TKI and its combined effects with EGFR intron 1 (CA)n polymorphism

BACKGROUND

Mutations in the epidermal growth factor receptor (EGFR) have been confirmed as predictors of efficacy for EGFR-tyrosine kinase inhibitors (TKIs). We investigated whether polymorphisms of the EGFR and cytochrome P450, family 1, member A1 (CYP1A1) genes were associated with clinical outcome in NSCLC patients treated with EGFR-TKI.

METHODS

Genotypes for the intron 1 (CA)n repeat and R497K polymorphisms in the EGFR gene and the *2A (3801 T→C) and *2C (2455 A→G) polymorphisms in CYP1A1 gene were evaluated in 115 NSCLC patients by PCR-RFLP and DNA sequencing. Genetic polymorphisms were correlated with clinical outcomes of EGFR-TKIs. From a subgroup of patients whose tumour tissues were available, associations between somatic EGFR mutations, EGFR expression, and genomic polymorphisms were also analysed.

RESULTS

EGFR intron 1 (CA)n and CYP1A1*2A polymorphisms were independent predictive factors (p=0.046, p=0.011, respectively) and the latter was also a prognostic factor (p=0.001) for patients treated with EGFR-TKIs. We also observed a strong synergistic effect from two genotypes. Specifically, patients with both the T/T allele of the CYP1A1 gene and shorter intron 1 CA repeats (≤ 16 CA) of the EGFR gene showed an improved response (p=0.002) compared with patients with the T/C or C/C allele and longer intron 1 CA repeats (both alleles >16 CA). In contrast, for R497K and CYP1A1*2C, no relationship was observed with clinical outcome for patients treated with EGFR-TKIs (p=0.573; p=0.629, respectively). Both SNPs in the CYP1A1 gene showed a correlation with EGFR somatic mutations.

CONCLUSIONS

The findings of this study suggest that the CYP1A1*2A polymorphism is a predictor for clinical outcome in NSCLC patients treated with EGFR-TKI therapy, and combining analysis of both CYP1A1*2A and EGFR intron 1 (CA)n polymorphisms may be useful for predicting treatment outcome in NSCLC patients treated with EGFR-TKIs.

Pharmacogenetic and germline prognostic markers of lung cancer

INTRODUCTION

Lung cancer is the leading global cause of cancer-related mortality. Interindividual variability in treatment response and cancer outcomes has focused attention on genetic polymorphisms as prognostic markers. We evaluated the overall contribution of candidate polymorphism association studies to our current understanding of the genetic predictors of lung cancer outcomes.

METHODS

We examined the results of 90 studies that evaluated associations between genetic polymorphisms and lung cancer outcomes published between January 1990 and May 2009.

RESULTS

A total of 170 genetic variations in 90 studies were identified. Overall survival was a primary outcome in 81% of the studies and toxicity in 19%. Candidate polymorphisms in the DNA repair/synthesis pathway were the most frequently studied. Strong evidence in large-scale confirmatory studies of any single polymorphism was lacking. Polymorphisms of EGFR, XRCC1, and ERCC1 were associated with pharmacogenetic outcomes, whereas polymorphisms of MDM2, p53, and GSTM1 were associated with prognostic outcomes. All remaining polymorphisms had results lacking or failing replication testing. Heterogeneity in study populations, incomplete reporting of important population or study characteristics, inadequate power, and inconsistencies in methodology were common.

CONCLUSIONS

Although the quality of existing studies involving the candidate polymorphism approach is highly variable, a small set of candidate polymorphisms was identified as potential biomarkers of clinical or pharmacogenetic outcome and would benefit from further replication testing. Newer approaches including haplotype tagging, pathway, genome-wide association, and combination methods with validative approaches may facilitate a more accurate prediction of lung cancer outcomes by genetic variation.

The Pharmacogenetic Rescue of Side-Lined Anticancer Drugs to the Front-Line: Gefitinib as a Case Example

OBJECTIVE

To illustrate the increasing importance of pharmacogenetics in drug development and clinical practice through a critical analysis of the validation and licensing of gefitinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, as a treatment for non-small cell lung cancer (NSCLC).

DATA SOURCES

Journal articles and the "grey" literature were identified through a systematic search of MEDLINE (to June 2010) and the Web sites of the major drug regulators. References identified through the reference lists of major published reviews of gefitinib and Erb receptors, including EGFR, were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

A broad appraisal of the titles and abstracts of articles on gefitinib and tyrosine kinase inhibitors in lung cancer was undertaken to identify pertinent concepts and relevant publications for further analysis. Articles deemed particularly relevant were retrieved for detailed appraisal. Dossiers on the licensing of gefitinib from the Food and Drug Administration Web site and major published reviews were retrieved. Relevant pharmacogenetic issues were identified and the clinical studies addressing these were evaluated.

DATA SYNTHESIS

Initial promising trial data for gefitinib in NSCLC led to its conditional marketing approval. When the drug's efficacy was not confirmed in a pivotal Phase 3 trial, its prescribing was restricted. Subsequent discovery of activating mutations in the tyrosine kinase domain of EGFR led to further retrospective and prospective evaluation of the drug in patients with those mutations. The new evidence was sufficiently robust to persuade the drug regulators to license the drug as first-line treatment for patients with locally advanced or metastatic NSCLC who test positive for those mutations.

CONCLUSIONS

Pharmacogenetic evidence has played a key role in rescuing gefitinib for front-line treatment of NSCLC. This case-example portends what will be increasingly likely scenarios in the regulation and clinical validation of targeted drug therapies.