anti-EGFR Therapy In Colorectal Cancer Research Articles

A qPCR gene expression module test to predict resistance to cetuximab in colorectal cancers independent of KRAS mutation status.

e14164 Background: While KRAS mutation predicts resistance to anti-EGFR therapy in colorectal cancer, not all KRAS wild-type patients benefit from such therapy, suggesting that complementary biomarkers capable of identifying additional non-responsive patients would have clinical utility. Methods: To search for such a biomarker, we studied the relationship of cetuximab response with twelve gene expression modules, derived from an unsupervised analysis of 20 independent microarray datasets comprising more than 2,000 colorectal cancer patients. Each module represents a set of highly co-expressed genes related to an important aspect of colorectal cancer variability. Two cetuximab-treated cohorts were studied. The first was a Phase II clinical trial (Khambata-Ford et al, J Clin Oncol, 2007) with accompanying microarray data from pre-treatment biopsies. The second was a single-institution study of cetuximab response from which formalin-fixed paraffin-embedded primary tumor specimens were available. Results: In the first study, module scores were computed by averaging co-expressed module genes in the microarray data. In the second study, module scores were generated from a qPCR gene expression module test, OncoScore Colon, which quantifies modules by averaging three representative module genes relative to housekeeping controls. Notably, in both studies, the mesenchymal module was significantly associated with cetuximab resistance, with module positive patients tending to progress on cetuximab within 10 weeks. Additionally, the status of this module was independent of KRAS mutation status—KRAS mutations occurred in both module-positive and -negative patients. Future clinical studies will continue to test the predictive capacity of the module in regards to cetuximab resistance and other mechanisms. Conclusions: In summary, this study demonstrates the value of a gene expression module-based qPCR panel for stratifying colorectal cancer patients for treatment response, and suggests that our approach may have immediate utility for cetuximab treatment response prediction.

Analysis of PTEN in patients with advanced colorectal cancer (CRC) receiving capecitabine alone or in combination with bevacizumab with or without mitomycin C in the phase III AGITG MAX trial.

3534 Background: There is an urgent need for potential biomarkers for anti-VEGF therapies. The tumour suppressor gene PTEN is thought to have a potential role as a biomarker for anti-EGFR therapy in CRC, but there is also evidence that decreased levels of PTEN leads to increased expression of VEGF suggesting a potential relationship to outcome with anti-VEGF therapy*. The prognostic value of PTEN also remains controversial. Methods: Patients enrolled in the Phase III MAX trial of capecitabine (C) +/- bevacizumab (B) (+/- mitomycin C (M)) with available tissue were analysed for PTEN expression (loss v no loss) as assessed using a Taqman copy number assay to measure copy number variation at the PTEN locus. PTEN status was correlated with progression-free survival (PFS) and overall survival (OS) outcomes. The predictive value of PTEN status for bevacizumab efficacy was also examined. Results: Of the original 471 patients enrolled in the trial, tissue from 302 (64.1%) patients were analysed. Baseline characteristics of those with and without tissue were comparable. PTEN loss was observed in 38.7% of patients. There was no relationship between PTEN loss and KRAS or BRAF mutation. Patients with PTEN loss were more likely to have rectal primary (p=0.01) and less likely to have lung metastasis (p=0.03). By using the comparison of C v CB+CBM, PTEN status was not significantly predictive of the effectiveness of B for PFS or OS (Table). PTEN status is also not prognostic for PFS or OS in multivariate analyses adjusting for other baseline factors (Table). Conclusions: PTEN status did not significantly predict different benefit with anti-VEGF therapy. PTEN status was also not prognostic for survival in advanced colorectal cancer. [Table: see text]

EGFR gene copy number assessment from areas with highest EGFR expression predicts response to anti-EGFR therapy in colorectal cancer

Background:Only 40–70% of metastatic colorectal cancers (mCRCs) with wild-type (WT) KRAS oncogene respond to anti-epidermal growth factor receptor (anti-EGFR) antibody treatment. EGFR amplification has been suggested as an additional marker to predict the response. However, improved methods for bringing the EGFR analysis into routine laboratory are needed.Methods:The material consisted of 80 patients with mCRC, 54 of them receiving anti-EGFR therapy. EGFR gene copy number (GCN) was analysed by automated silver in situ hybridisation (SISH). Immunohistochemical EGFR protein analysis was used to guide SISH assessment.Results:Clinical benefit was seen in 73% of high (⩾4.0) EGFR GCN patients, in comparison with 59% of KRAS WT patients. Only 20% of low EGFR GCN patients responded to therapy. A high EGFR GCN number associated with longer progression-free survival (P<0.0001) and overall survival (P=0.004). Together with KRAS analysis, EGFR GCN identified the responsive patients to anti-EGFR therapy more accurately than either test alone. The clinical benefit rate of KRAS WT/high EGFR GCN tumours was 82%.Conclusion:Our results show that automated EGFR SISH, in combination with KRAS mutation analysis, can be a useful and easily applicable technique in routine diagnostic practise for selecting patients for anti-EGFR therapy.

Reply: Cetuximab in small bowel adenocarcinoma: a new friend?

Sir, We appreciate the comments and data provided by Santini et al based upon our recent report (Overman et al, 2010; Figure 1). The use of anti-EGFR therapy in small bowel adenocarcinoma (SBA) is rationale, based upon the high-level expression of the target and known activity of this agent in adenocarcinomas of the large intestine. Though small and large intestinal adenocarcinomas differ dramatically in incidence, a number of similarities in clinical behaviour, such as metastatic site predilection and chemotherapy responsiveness, do exist. As activating mutations in the Kras oncogene are critical in determining the activity of anti-EGFR therapy in colorectal cancer, molecular testing for mutations in the Kras gene must also be incorporated into the assessment of anti-EGFR therapy in SBA. Figure 1 Pre-treatment (A) and post-treatment (B) computed tomography images showing radiographic response to single agent cetuximab in a patient with metastatic duodenal adenocarcinoma. In the commentary by Santini et al, an impressive radiographic response of 75% was observed in four patients treated with the combination of cetuximab and irinotecan in a primarily Kras wild-type SBA population. As mentioned by the authors, this finding is encouraging and appears improved over the response rates observed with 5-fluorouracil and irinotecan combinations (Zaanan et al, 2010). However, the contributory effect of cetuximab cannot be determined as cetuximab was combined with a known active agent in SBA. We have recently treated a 67-year-old man with metastatic moderately differentiated adenocarcinoma of the duodenum to liver and retroperitoneal lymph nodes with single-agent cetuximab (500 mg m−2 every other week) as the fourth-line therapy. After 8 weeks, a 24% reduction in tumour size per RECIST criteria was observed. The pre-treatment (A) and post-treatment (B) computed tomography images are shown in accompanying figure. The subsequent treatment course was complicated by cholangitis and radiographic progression occurred after 20 weeks. We agree with Santini et al that further prospective studies are needed to determine the role of anti-EGFR therapy in SBA. In an attempt to build upon our previous work with the combination of capecitabine and oxaliplatin, CAPOX (Overman et al, 2009), we are currently initiating a phase II study evaluating the combination of panitumumab with CAPOX as the first-line treatment for advanced SBA with wild-type Kras.

Lessons from PETACC 2: No prognostic impact of KRAS-/BRAF-status in stage III colon cancer treated with adjuvant 5-FU monotherapy.

3591 Background: KRAS and possibly BRAF mutations are negative predictors for anti-EGFR therapy in colorectal cancer. The prognostic impact of these mutations is less clear. This study aimed to assess the correlation of KRAS/BRAF status with morphological characteristics and its prognostic impact for long-term outcome in UICC stage III colon cancer (CC). Methods: FFPE material from 493 patients treated with adjuvant 5-FU/FA in the PETACC2 trial (ClinicalTrials.gov NC4150) was collected retrospectively. KRAS mutations were detected by direct sequencing (ABI Prism 310), BRAF mutations by pyrosequencing (Pyromark Q24). Statistical analysis was done using Fisher exact test and Kaplan Meier survival analyses (level of significance:0.05). Results: Neither KRAS nor BRAF mutations were associated with patient age or patient sex. KRAS mutations did also not correlate with any pathological parameters. BRAF mutations, however, were significantly more frequent in mucinous (n = 12/45; 26.7%) than in nonmucinous c...

Anti-Egfr Therapy in Colorectal Cancer: How to Choose The Right Patient

The anti-epidermal growth factor receptor monoclonal antibodies cetuximab and panitumumab have established efficacy as single agent and in combination with chemotherapy in advanced colorectal cancer. However, only a small percentage of unselected patients (around 10%) are responsive to these costly agents. Mutations in the KRAS gene are associated with resistance to both cetuximab and panitumumab and account for approximately 30% to 40% of resistant patients. Nevertheless, having an intact KRAS is necessary but not sufficient to derive benefit from EGFR inhibition. Further, positive predictive markers that are currently being evaluated include an increase in EGFR gene copy number and additional data suggest that other EGFR downstream pathways such as the PI3K/PTEN/AKT/mTOR and JAK/STAT pathways are also important when considering mechanisms of EGFR antibody resistance. New data seem to support the role of BRAF mutational status. In addition, high mRNA levels of the EGFR-ligands Epiregulin and Amphiregulin have been associated with increased responsiveness to cetuximab. In this article we will review the available clinical and experimental data potentially useful for a better patients' selection.

Phenotypic and genotypic characteristics of epidermal growth factor receptor (EGFR) in colorectal cancer patients

4110 Background: Colorectal tumors express EGFR and are responsive to anti-EGFR therapies. However, there is no tumoral predictive factor for anti-EGFR therapy in colorectal cancer and EGFR gene copy number is currently a good candidate. The aim of this study was to examine relationships between EGFR germinal polymorphisms, EGFR gene copy number and EGFR expression. Methods: Eighty primary colorectal tumors were analyzed along with 39 normal mucosas. Tumor staging was : 4 stage 0, 13 stage I, 22 stage II, 23 stage III and 18 stage IV. EGFR -216G&gt;T and -191C&gt;A genotypes were analyzed by PCR-RFLP, CA-repeats polymorphism in intron 1 by fluorescent genotyping and gene copy number was measured by PCR amplification. EGFR expression was quantified with the reference Scatchard binding assay giving high- and low-affinity sites along with Kd values (Francoual M et al. Ann Oncol 17, 2006). Results: The number of CA- repeats varied from 14 to 21. Considered genotypes were superimposable between tumoral and normal tissues. A linkage disequilibrium was noted between -216G&gt;T and -191C&gt;A genotypes (p = 0.011). CA-repeats polymorphism and -216G&gt;T genotype were not independent (p = 0.002). No relationship was observed between any of the analyzed EGFR genotypes and EGFR expression. EGFR expression was not related to gene amplification. EGFR gene amplification in tumor and normal tissue varied over a 4.7- and 2.9-fold range, respectively, and were not correlated. The mean value of the tumor/normal mucosa amplification ratio was 1.16 (range 0.55–2.68) and 14% of patients exhibited lower amplification in the tumor relative to the normal mucosa (ratio &lt; 0.75). The mean ratio of high-affinity sites between tumor and normal mucosa was 1.20 (range 0.03–13.33). Conclusions: In colorectal tumors, neither EGFR gene amplification nor EGFR germinal gene polymorphisms influenced EGFR expression quantified with a specific ligand-binding assay. No significant financial relationships to disclose.