Samuel Murray

Assessment of somatic k-RAS mutations as a mechanism associated with resistance to EGFR-targeted agents: a systematic review and meta-analysis of studies in advanced non-small-cell lung cancer and metastatic colorectal cancer

BACKGROUND Somatic mutations of the k-RAS oncogene have been assessed as a mechanism of de-novo resistance to epidermal growth factor receptor (EGFR) tyrosine-kinase inhibition in patients with non-small-cell lung cancer (NSCLC), and to anti-EGFR monoclonal antibodies in patients with metastatic colorectal cancer (mCRC). The aim of this systematic review and meta-analysis was to assess if k-RAS mutations represent a candidate predictive biomarker for anti-EGFR-targeted therapeutic strategies in mCRC and NSCLC. METHODS We systematically identified articles pertaining to k-RAS mutational status in patients with NSCLC treated with tyrosine-kinase inhibitors (TKI), and patients with mCRC treated with any anti-EGFR-based regimens. Eligible studies had to report complete responses (CR) and partial responses (PR), stratified by k-RAS mutational status. Potential between-study heterogeneity was accommodated by use of random-effects models for bivariable meta-analysis of sensitivity and specificity (the primary endpoints). The positive and negative likelihood ratios (+LR and -LR, respectively) of k-RAS mutations for predicting an absence of response were considered as secondary endpoints and were calculated by use of pooled estimates for sensitivity and specificity. FINDINGS Of 252 retrieved manuscripts, 17 were deemed eligible for the NSCLC meta-analysis (165 of 1008 patients with mutated k-RAS). The presence of k-RAS mutations was significantly associated with an absence of response to TKIs (sensitivity=0.21 [95% CI 0.16-0.28], specificity=0.94 [0.89-0.97]; +LR=3.52; -LR=0.84). Of 68 retrieved manuscripts reporting on anti-EGFR monoclonal-antibody-based treatment of mCRC, eight studies were deemed eligible for the final analysis (306 of 817 patients with mutated k-RAS). The presence of k-RAS mutations was significantly associated with an absence of response to anti-EGFR monoclonal-antibody-based treatments (sensitivity=0.47 [0.43-0.52]; specificity=0.93 [0.83-0.97]; +LR=6.82; -LR=0.57). INTERPRETATION This analysis provides empirical evidence that k-RAS mutations are highly specific negative predictors of response (de-novo resistance) to single-agent EGFR TKIs in advanced NSCLC; and similarly to anti-EGFR monoclonal antibodies alone or in combination with chemotherapy in patients with mCRC. The low sensitivity and relatively high -LR of k-RAS mutations for determining non-responsiveness clearly shows that additional mechanisms of resistance to EGFR inhibitors exist.

Trastuzumab in the Adjuvant Treatment of Early-Stage Breast Cancer: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND We performed a systematic review and meta-analysis to compare treatment outcomes for human epidermal growth factor receptor (HER)-2-positive breast cancer patients receiving adjuvant chemotherapy with or without trastuzumab. METHODS We identified randomized clinical trials comparing adjuvant chemotherapy with or without trastuzumab in patients with resectable breast cancer. Fixed-effects meta-analysis was used to combine data. RESULTS Five eligible trials were identified, reporting outcomes on 13,493 women. Fixed-effects analysis showed disease-free survival to be superior for trastuzumab-treated patients (risk ratio [RR], 0.62; 95% confidence interval [CI], 0.56-0.68). Superiority was also observed for patients receiving trastuzumab with respect to mortality (RR, 0.66; 95% CI, 0.57-0.77), locoregional recurrence (RR, 0.58; 95% CI, 0.43-0.77), and distant recurrence (RR, 0.60; 95% CI, 0.52-0.68). Patients receiving trastuzumab with chemotherapy had a higher risk for congestive heart failure (RR, 7.60; 95% CI, 4.07-14.18) and left ventricular ejection fraction decline (RR, 2.09; 95% CI, 1.84-2.37). A higher risk for central nervous system metastasis as the first recurrence event (RR, 1.60; 95% CI, 1.06-2.40) was also noted in patients receiving trastuzumab. CONCLUSIONS The use of trastuzumab should be considered an integral part of the adjuvant therapy of HER-2-positive breast cancer patients.

Somatic EGFR mutations and efficacy of tyrosine kinase inhibitors in NSCLC

Early clinical studies of tyrosine kinase inhibitors (TKIs) that target the EGFR in patients with advanced non-small-cell lung cancer (NSCLC) showed that some patients experienced rapid, durable, complete or partial responses. These data were the basis for attempts to identify specific subgroups of patients who would further benefit from these agents. The discovery of somatic mutations in EGFR that correlated with sensitivity to TKIs identified a plausible explanation for these observations. Clinical and pathological factors such as female sex, never having smoked, Asian origin and adenocarcinoma histology correlate with the presence of EGFR mutations and objective responses to TKIs in patients with NSCLC. Recent studies in metastatic colorectal cancer highlighted that somatic mutations in KRAS represent a negative predictor of response to anti-EGFR monoclonal antibodies; KRAS mutations also represent an important mechanism of resistance to TKIs in NSCLC. Many large clinical studies are currently investigating the predictive and prognostic value of EGFR mutational status and other candidate biomarkers. We summarize the literature and present an overview of the field of anti-EGFR therapy in NSCLC, focusing on the influence of somatic EGFR mutations on selection of patients for TKI therapy and the influence of EGFR pathway regulation.

Taxane resistance in breast cancer: Mechanisms, predictive biomarkers and circumvention strategies

BACKGROUND Taxanes are established in the treatment of metastatic breast cancer (MBC) and early breast cancer (EBC) as potent chemotherapy agents. However, their therapeutic usefulness is limited by de-novo refractoriness or acquired resistance, which are common drawbacks to most anti-cancer cytotoxics. Considering that the taxanes will remain principle chemotherapeutic agents for the treatment of breast cancer, we reviewed known mechanisms of resistance in with an outlook of optimizing their clinical use. METHODS We searched the PubMed and MEDLINE databases for articles (from inception through to 9th January 2012; last search 10/01/2012) and journals known to publish information relevant to taxane chemotherapy. We imposed no language restrictions. Search terms included: cancer, breast cancer, response, resistance, taxane, paclitaxel, docetaxel, taxol. Due to the possibility of alternative mechanisms of resistance all combination chemotherapy treated data sets were removed from our overview. RESULTS Over-expression of the MDR-1 gene product Pgp was extensively studied in vitro in association with taxane resistance, but data are conflicting. Similarly, the target components microtubules, which are thought to mediate refractoriness through alterations of the expression pattern of tubulins or microtubule associated proteins and the expression of alternative tubulin isoforms, failed to confirm such associations. Little consensus has been generated for reported associations between taxane-sensitivity and mutated p53, or taxane-resistance and overexpression of Bcl-2, Bcl-xL or NFkB. In contrary sufficient in vitro data support an association of spindle assembly checkpoint (SAC) defects with resistance. Clinical data have been limited and inconsistent, which relate to the variety of methods used, lack of standardization of cut-offs for quantitation, differences in clinical endpoints measured and in methods of tissue collection preparation and storage, and study/patient heterogeneity. The most prominent finding is that pharmaceutical down-regulation of HER-2 appears to reverse the taxane resistance. CONCLUSIONS Currently no valid practical biomarkers exist that can predict resistance to the taxanes in breast cancer supporting the principle of individualized cancer therapy. The incorporation of several biomarker analyses into prospectively designed studies in this setting are needed.

Somatic EGFR Mutation and Gene Copy Gain as Predictive Biomarkers for Response to Tyrosine Kinase Inhibitors in Non–Small Cell Lung Cancer

Purpose: The aim of this systematic review and meta-analysis was to characterize common EGFR molecular aberrations as potential predictive biomarkers for response to monotherapy with tyrosine kinase inhibitors (TKI) in non–small cell lung cancer (NSCLC). Experimental Design: We systematically identified articles investigating EGFR status [somatic mutational and gene copy aberrations (copy number)] in patients with NSCLC treated with TKIs. Eligible studies had to report complete and partial response rates stratified by EGFR status. We used random effects models for bivariable meta-analysis of sensitivity and specificity; positive and negative likelihood ratios (+LR and −LR, respectively) were also calculated and were considered as secondary end points. Results: Among 222 retrieved articles, 59 were considered eligible for the somatic EGFR mutation meta-analysis (1,020 mutations among 3,101 patients) and 21 were considered eligible for the EGFR gene copy number meta-analysis (542 gene gain among 1,539 patients). EGFR mutations were predictive of response to single-agent TKIs [sensitivity, 0.78; 95% confidence interval (95% CI), 0.74-0.82; specificity, 0.86; 95% CI, 0.82-0.89; +LR, 5.6; −LR, 0.25]. EGFR gene gain was also associated with response to TKIs, albeit with lower sensitivity and specificity. In subgroup analysis, the only recognized trend was for a higher predictive value in Whites compared with East Asians for both mutation and gene copy number. Conclusion: This analysis provides empirical evidence that EGFR mutations are sensitive and specific predictors of response to single-agent epidermal growth factor receptor TKIs in advanced NSCLC. The diagnostic performance of mutations seems better than that of EGFR gene gain. Clin Cancer Res; 16(1); 291–303

Molecular genetic tools shape a roadmap towards a more accurate prognostic prediction and personalized management of cancer

The continuous flow of molecular genetic information has cautiously started integrating into clinical practice changing the future landscape of the clinical management of cancer. Germline mutation analysis for individuals at familial risk and testing result-based surgical or non-surgical preventive intervention can protect from hereditary breast-ovarian, colorectal and stomach cancer and reduce mortality. Research is focusing now on the development of effective chemoprevention to replace prophylactic surgery for improving quality of life and to provide novel targeted therapies for hereditary cancer patients. The TNM staging system and conventional clinicopathologic factors have led clinical decisions on adjuvant therapy for decades improving survival in patients with early-stage tumors. However, current staging methods and therapeutic decisions remain suboptimal. Patients with early-stage cancer who are at low risk of recurrence could be spared the toxicity of systemic treatment if clearly distinguished, while others at high risk of distant recurrence could get maximal benefit if therapy matched the molecular genetic profile of either the host or the tumor. With the establishment of validated molecular analysis techniques it is believed that clinical biomarkers will gradually overtake TNM by their capacity to form more accurate prognostic systems and delineate better predictors of response to specific therapies. Areas of cancer research such as germ-cell mutation analysis, tumor gene-signature identification, gene expression profile linked targeted therapy, cancer stem cells, circulating cancer cells and single-nucleotide polymorphism keep on producing promising data which is believed to refine future preventive and early intervention strategies on an individual basis. Today these gene-based strategies are in a transition phase prior to full implementation into clinical practice. At present they wait for the results of large-scale prospective validation studies which compare molecular against “classic” markers. It is anticipated that molecular genetic biomarkers when implemented in clinical practice will considerably improve both biologically guided therapeutic decisions and clinical outcomes.

Somatic Mutations of the Tyrosine Kinase Domain of Epidermal Growth Factor Receptor and Tyrosine Kinase Inhibitor Response to TKIs in Non-small Cell Lung Cancer: An Analytical Database

Background: After the discovery of somatic mutations in the tyrosine kinase domain (exons 18–24) of the epidermal growth factor receptor (EGFR) correlating with responses of non-small cell lung cancer (NSCLC) to the tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib, there has been increasing interest in utilizing this molecular marker for treatment selection. We aimed to analytically catalogue the mutational spectrum of somatic mutations in EGFR and format a database allowing correlation of specific mutations with clinico-pathologic factors and response to TKIs. Methods: A computerized search of MEDLINE (January 1, 2004 to June 30, 2007) was performed to identify articles reporting on NSCLC patients harboring somatic mutations in EGFR. Demographic, clinico-pathologic, mutational, and response data were extracted and tabulated. Results: A total of 202 eligible articles were identified. We report data on 12,244 patients with 3381 somatic EGFR mutations. The majority of mutations have been reported on only one occasion (158 of 254, 62.2%), and only nine mutations occur at a rate of ≥1%. L858R and delE746-A750 account for 32.84% and 24.28% of all mutations, respectively; with 50% of mutations being exon 19 deletions or “deletional-insertions.” There is a clear association between the presence of mutations and response to TKI. Conclusions: We have generated a free access, nonprofit online analytical database of somatic EGFR mutations in NSCLC. Cumulative information will be made available through a routine update of both database tables and associated graphical representations. Direct updates and submissions through the online site (www.somaticmutations-EGFR.org) are encouraged, as are comments and suggestions.

EGFR gene copy number as a predictive biomarker for patients receiving tyrosine kinase inhibitor treatment: a systematic review and meta-analysis in non-small-cell lung cancer.

INTRODUCTION We conducted a systematic review and meta-analysis to assess epidermal growth factor receptor (EGFR) gene copy number as a potential biomarker of survival for patients with advanced non-small-cell lung cancer (NSCLC) receiving single-agent treatment with EGFR tyrosine kinase inhibitors (TKIs). METHODS We systematically identified articles investigating EGFR gene copy number by fluorescent or chromogenic in situ hybridization in patients with advanced or recurrent NSCLC treated with the TKIs erlotinib or gefitinib, (last search: 31 June 2009). Eligible studies had to report on overall survival (OS), progression-free survival (PFS) or time-to-progression (TTP), stratified by EGFR gene copy number. Summary hazard ratios (HRs) were calculated using random-effects models. RESULTS Among 255 identified studies, 20 (1689 patients, 594 with increased gene copy number), 10 (822 patients, 290 with increased gene copy number) and 5 (294 patients, 129 with increased gene copy number) were eligible for the OS, PFS and TTP meta-analyses, respectively. Increased EGFR gene copy number was associated with increased OS (HR = 0.77; 95% CI 0.66-0.89; P = 0.001), PFS (HR = 0.60; 95% CI 0.46-0.79; P<0.001) and TTP (HR = 0.50; 95% CI 0.28-0.91; P = 0.02). Among predominantly white populations, increased EGFR gene copy number was strongly associated with improved survival (HR = 0.70; 95% CI 0.59-0.82; P<0.001), whereas it did not influence survival in East Asians (HR = 1.11; 95% CI 0.82-1.50; P=0.50). This difference was statistically significant (P=0.02). CONCLUSION Among TKI-treated patients, increased EGFR gene copy number appears to be associated with improved survival outcomes. The effect on OS appears to be limited to patients of non-Asian descent.

Gemcitabine Combined with Gefitinib in Patients with Inoperable or Metastatic Pancreatic Cancer: A Phase II Study of the Hellenic Cooperative Oncology Group with Biomarker Evaluation

The combination of gemcitabine and gefitinib was evaluated in advanced pancreatic cancer. Totally, 53 patients were treated with a 7 week cycle of gemcitabine (1,000 mg/m2 given weekly) followed by six 4 week cycles of gemcitabine given on days 1, 8 and 15. Gefitinib 250 mg was administered daily. Responses were seen in 6, and stabilization of the disease in 12 patients. The main toxicity was myelotoxicity (92%). The 6-month progression-free survival (PFS) was 30%. Median PFS was 4.1 months and median survival 7.3 months with a 1 year survival rate of 27%. The above combination demonstrated promising activity in advanced pancreatic cancer.

TP53 Arg72Pro polymorphism and colorectal cancer risk: a systematic review and meta-analysis.

Background: The TP53 rs1042522 polymorphism (c.215C>G, Arg72Pro) has been extensively investigated as a potential risk factor for colorectal cancer, but the results have thus far been inconclusive. Methods: We searched multiple electronic databases to identify studies investigating the association between the Arg72Pro polymorphism and colorectal cancer. Individual study odds ratios (OR) and their confidence intervals were estimated using allele-frequency, recessive, and dominant genetic models. Summary ORs where estimated using random effects models. Results: We identified 23 eligible case-control studies, investigating 6,514 cases and 9,334 controls. There was significant between-study heterogeneity for all genetic models. The control group in one of the studies was not in Hardy-Weinberg equilibrium; only three studies reported that genotyping was blinded to case/control status and five studies used tumor tissue for case genotyping. Overall, we did not identify any association between rs1042522 and colorectal cancer risk under an allele-frequency comparison (OR, 0.99; 95% confidence interval, 0.89–1.09). Likewise, no association was evident under dominant or recessive models. Studies using tumor tissue for case genotyping found a protective effect for the Pro allele, compared with studies using somatic DNA (Pinteraction = 0.03). Results were also inconsistent between different genotyping methods (Pinteraction = 0.03). Conclusion: We did not identify an association between TP53 rs1042522 and colorectal cancer. Published results seem to be driven by technical artifacts rather than true biological effects. Impact: Future genetic association studies should use more rigorous genotyping methods and avoid the use of tumor tissue as a source of DNA to prevent genotype misclassification due to loss of heterozygosity. Cancer Epidemiol Biomarkers Prev; 19(7); 1840–7. ©2010 AACR.