KRAS Gene Mutation Status Research Articles

Correction: Spectrum of EGFR Gene Copy Number Changes and KRAS Gene Mutation Status in Korean Triple Negative Breast Cancer Patients

Correction: Spectrum of EGFR Gene Copy Number Changes and KRAS Gene Mutation Status in Korean Triple Negative Breast Cancer Patients

P-0171 - Incidence of Kirsten-Ras Gene Mutation and its Association with Clinical and Pathological Factors in Colorectal Carcinoma: Single Institute Retrospective Experience

Introduction: Colorectal carcinoma (CRC) is the third most common cause of cancer in males and the second in females. Kirsten-RAS (K-ras) is a gene that encodes one of the proteins in the epidermal growth factor receptor (EGFR) signalling pathway. Mutation in K-ras gene in patients with colorectal adenocarcinoma develops early in the progression from adenoma to carcinoma. K-ras gene mutation status in metastatic colorectal cancers (mCRC) is predictive of response to anti-epidermal growth factor receptor therapies, such as cetuximab and panitumumab. Thus the present study is carried out to detect the incidence and clinic pathological profile of the K-ras gene mutation in our institute. Methods: A retrospective study was conducted to evaluate the incidence and clinic pathological profile with reference to K-ras gene status in patients with colorectal carcinoma who had been treated and undergone K ras Mutation analysis by Polymerase Chain Reaction (PCR) technique on the formalin fixed paraffin embedded tumour blocks. Study was conducted over a period of five years from January 2009 to December 2013 in Department of Medical Oncology in our institute. Correlation of clinical and pathological factors with K-ras gene mutation was done. Results: In 74 Of 144 patients with colorectal carcinoma who underwent K ras Mutation analysis, The frequency of K-ras gene mutation in CRC was 25.67% (19) with 89.5%(17) of these mutations occurring on codon 12 and 10.5% (2) on codon 13. The wild type K-ras gene was seen in 74.32%(55) of CRC. The median age was 51 years in the CRC patients with mutant K-ras gene. The male: female ratio of mutated K-ras gene was 1.37: 1. Out of the 34 CRC patients with lymph node metastases, 29.4% of them were mutant K-ras gene. In eleven patients with Stage IV CRC with K-ras gene mutation, liver was only site of distant metastases. Conclusion: This study has shown that K-ras gene mutations are common among colorectal adenocarcinoma patients. There was no significant statistical correlation between the mutated K-ras gene and age, gender, tumour location, tumour histology, lymph node metastases and distant metastases which may be attributable to the relatively small sample size.

Spectrum of EGFR Gene Copy Number Changes and KRAS Gene Mutation Status in Korean Triple Negative Breast Cancer Patients

Anti-epidermal growth factor receptor (EGFR) therapy has been tried in triple negative breast cancer (TNBC) patients without evaluation of molecular and clinical predictors in several randomized clinical studies. Only fewer than 20% of metastatic TNBCs showed response to anti-EGFR therapy. In order to increase the overall response rate, first step would be to classify TNBC into good or poor responders according to oncogenic mutation profiles. This study provides the molecular characteristics of TNBCs including EGFR gene copy number changes and mutation status of EGFR and KRAS gene in Korean TNBC patients. Mutation analysis for EGFR, KRAS, BRAF and TP53 from a total of 105 TNBC tissue samples was performed by direct sequencing, peptide nucleic acid-mediated PCR clamping method and real-time PCR. Copy number changes of EGFR gene were evaluated using multiplex ligation-dependent probe amplification. Out of all 105 TNBCs, 15.2% (16/105) showed EGFR copy number changes. Among them, increased or decreased EGFR copy number was detected in 13 (5 single copy gain, 2 amplification and 4 high-copy number amplification) and 3 cases (3 hemizygous deletion), respectively. The mutation frequencies of KRAS, EGFR and TP53 gene were 1.9% (G12V and G12D), 1.0% (exon 19 del) and 31.4%, respectively. There was no BRAF V600E mutation found. Future studies are needed to evaluate the clinical outcomes of TNBC patients who undergo anti-EGFR therapy according to the genetic status of EGFR.

Impact of KRAS mutational status on clinical outcomes in patients receiving capecitabine based chemotherapy.

436 Background: Mutations affecting the KRAS gene are established predictive markers of outcome with anti–epithelial growth factor receptor antibodies in metastatic colorectal cancer (mCRC). The relevance of these markers for chemotherapy has not been established. This analysis was performed to assess the predictive impact of KRAS mutation status in patients receiving chemotherapy. Methods: KRAS mutational status was available for 223 patients treated for mCRC. Predictive analysis of mutational status by type of fluoropyrmidine the 1st-line regimen contained (either capecitabine [C] based chemotherapy or infusional 5Fluorouracil [I-5Fu]) for clinical outcomes: progression-free survival (PFS), time to chemotherapy resistance (TTCR) and overall survival (OS). Results: KRAS mutations were observed in 43.5% of the patients. 165 patients received I-5Fu, 44 patients received C. KRAS mutation status (wild type [WT] v mutated [MT]) had no prognostic impact for OS (hazard ratio [HR], 0.81; CI, 0.69 to 1.1 p=0.17) for PFS (hazard ratio [HR], 0.87; CI, 0.66 to 1.14 p=0.3) and TTCR (hazard ratio [HR], 0.85; CI, 0.65to 1.12 p=0.26). C based 1st-line chemotherapy vs. I- 5FU based was predictive of PFS (hazard ratio [HR], 0.52; CI, 0.37 to 0.74 p=0.0003) and TTCR (hazard ratio [HR], 0.54; CI, 0.38 to 0.75p=0.0005) and not of OS (hazard ratio [HR], 0.74; CI, 0.52 to 1.1 p=0.1). KRAS mutational status had predictive impact in patients receiving C based 1st-line chemotherapy on OS (hazard ratio [HR], 0.47; CI, 0.23 to 0.948 p<0.0001) TTCR (hazard ratio [HR], 0.49; CI, 0.25 to 0.97 p=0.0398) and was not predictive of PFS (hazard ratio [HR], 0.78; CI, 0.4 to 1.53 p=0.47) Conclusions: KRAS gene mutation status was predicitve for OS and for TTCR in patients who received C based 1st-line chemotherapy.

Clinical-Pathological Correlation of KRAS Mutation Status in Metastatic Colorectal Adenocarcinoma

BackgroundKRAS gene mutations play an important role in the carcinogenesis of colorectal tumors. However, studies that have assessed the association between KRAS gene mutation status and disease characteristics report conflicting results. To assess KRAS gene status (mutated or wild-type) and its association with the clinical, epidemiological, and histopathological features of metastatic colorectal adenocarcinoma as well its association with clinical outcomes.MethodsCross-sectional descriptive study in which clinical and histopathological data were collected from the medical records of 65 patients diagnosed with metastatic colorectal adenocarcinoma at the Clinical Oncology Service of the Teaching Hospital of the School of Medicine of Ribeirao Preto, University of Sao Paulo (Hospital das Clinicas da Faculdade de Medicina de Ribeirao Preto, Universidade de Sao Paulo -HCFMRP-USP) between 2005 and 2012 and analyzed based on their KRAS gene status.ResultsKRAS gene mutations were found in 49.2% of the tumors, and G/A (25.5%) and Gly12Asp (34.37%) were the most frequent mutations. Among the investigated clinical features (gender, ECOG (Eastern Cooperative Oncology Group), histology, degree of cell differentiation, lymph node ratio, primary tumor site, staging, presence of synchronous metastasis, lung metastasis, and liver metastasis), the association between age less than 65 years with KRAS mutation was statistically significant (P = 0.046). KRAS mutation status did not exhibit a significant correlation with the overall survival of the patients (P = 0.078); however, the cases with KRAS mutation exhibited shorter survival. In the multivariate analysis, synchronous metastasis (P = 0.03) and liver metastasis (P = 0.008) behaved as independent factors of poor prognosis relative to the overall survival of the patients.ConclusionThe KRAS mutation status did not exhibit prognostic value in the investigated sample. Among the older patients (> 65 years old), wild-type KRAS was more frequently observed compared to mutated KRAS.

EGFR and K-ras gene mutation status in squamous cell anal carcinoma: a role for concurrent radiation and EGFR inhibitors?

Background:There is a growing appreciation for radio-sensitiser use in multi-modal cancer treatment models. Squamous cell anal carcinoma (SCAC) is a rare gastrointestinal tumour traditionally treated with concurrent chemotherapy and radiation. Cetuximab, an epidermal growth factor receptor (EGFR) inhibitor, has demonstrated significant efficacy when combined with radiation in squamous cell carcinoma of the head and neck (SccH&N). We wanted to assess EGFR and Kirsten-ras (K-ras) status in SCAC to see whether it compares with SccH&N.Methods:Over 90 SCAC paraffin-embedded biopsies were mounted onto a tissue microarray and were assessed for EGFR expression by immunohistochemistry. These samples were also assessed for the most frequently mutated K-ras and EGFR exons by high-resolution melting analysis.Results:The EGFR was present in over 90% of samples tested. The K-ras and EGFR mutations were absent in all samples tested, although a synonymous single-nucleotide polymorphism was found in 3 out of 89 samples tested for EGFR exon 19.Conclusion:The low rate of K-ras and EGFR mutations, coupled with the high surface expression of EGFR, suggests similarity in the EGFR signalling pathway between SCAC and SccH&N, and thus a potential role for EGFR inhibitors in SCAC. To our knowledge this is the largest cohort of invasive SCAC samples investigated for EGFR and K-ras mutations reported to date.

K-Ras gene mutation status as a prognostic and predictive factor in patients with colorectal cancer undergoing irinotecan- or oxaliplatin-based chemotherapy

Background: CRC caused more than 600,000 estimated deaths in 2008. Dysregulated signaling through the RAS/RAF/mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway due to mutations in K-Ras and B-Raf are common events in CRC. Methods: Incidence of mutations in codons 12 and 13 of K-Ras and exons 11 and 15 of B-Raf were analyzed in amplified PCR products from primary tumors of 273 patients with CRC, and their prognostic and predictive significance was assessed. The prognostic role of clinical and pathological factors was also examined. Results: K-Ras mutations were present in 89 patients (32.6%), of whom 76 (85.4%) had mutations in codon 12 and 10 (11.2%) had mutations in codon 13. B-Raf gene mutations were present in 17 patients (6.9%), of whom 6 (35.3%) had mutations in exon 15. Multivariate analysis revealed a predictive significance for K-Ras mutations with respect to time to progression in patients treated with irinotecan and oxaliplatin as first-line chemotherapy. There was no predictive significance for B-Raf gene mutation status in these patients. The following risk factors were found to affect overall survival (OS) rates: primary tumor location, lymph node involvement grade, carcinoembryonic antigen (CEA) level before treatment, and performance status according to WHO criteria. Conclusions: Based on the results of this study, K-Ras mutation status may be a suitable indicator of patient eligibility and a prognostic indicator for responsiveness to anti-EGFR therapy alone, or in combination with chemotherapy. Also, K-Ras mutation status may predict time to progression in patients treated with irinotecan and oxaliplatin.

Bevacizumab in combination with chemotherapy in the first-line treatment of metastatic colorectal carcinoma

Colorectal carcinoma (CRC) is a malignancy of worldwide increased incidence. The vast majority of all CRC cases occur in patients older than age 50. The initial stage at the time of diagnosis has a strong influence on the overall survival (OS). According to AJCC sixth edition system, 5-year stage-specific survivals are over 90% in stage I, but only approximately 8% in stage IV [1]. Chemotherapy in combination with biological treatment has improved response rates (RR), with prolongation of progression free survival (PFS) and OS. Important role in treatment of metastatic colorectal carcinoma (mCRC) plays surgical resection of metastases. Multidisciplinary cooperation between medical oncologist, surgeon, radiologist and radiotherapist is necessary to achieve the best therapeutic results. The aim of our analysis was to describe the efficacy of bevacizumab used in combination with chemotherapy in the first-line setting and to evaluate frequency of thromboembolic complications during the treatment. The analysis included 58 patients with mCRC, who have been treated with first-line chemotherapy in combination with bevacizumab at the St. Elizabeth Cancer Institute in Bratislava since 2006 and first assessed for the first therapeutic results in October 2010. The clinical benefit after the treatment represented by overall response rate (ORR) and stable disease (SD) was achieved in 87.93% of patients, and surgical resection of metastases after therapy underwent 12.07% of patients. Median time to progression (TTP) was 8 months and median OS evaluated in October 2011 was 27 months. Mutation status of KRAS gene had no influence on the effectiveness of treatment and BRAF mutations exhibited a strong negative prognostic significance. Thromboembolic complications were present in 17.24%.

Review of biomarkers in colorectal cancer

Advances in molecular technology have resulted in the discovery of many putative biomarkers relevant to colorectal cancer (CRC). Literature searches were performed on PubMed and EMBASE using the words 'colorectal cancer', AND 'biomarkers OR markers'. Biomarkers that are either currently in clinical use or have potential clinical use were identified. Most potential markers are in the discovery phase waiting to undergo clinical validation. Hypermethylation of the plasma septin-9 gene shows promise as a nonstool-based screening tool. Hypermethylation of the DYPD gene (encodes the enzyme dihydropyrimidine dehydrogenase) and variation of the uridine diphosphate-glucuronosyltransferase 1A (UGT1A1) gene have predictive value for side effects and the efficacy of 5-fluoruracil and irinotecan, respectively. Mismatch repair protein immunohistochemistry is able to predict response to 5-fluorouracil, and the KRAS (Kirsten rat sarcoma viral oncogene) and B-RAF (v-RAF murine sarcoma viral oncogene homolog B1) somatic gene mutation status can predict the response to anti-epidermal growth factor receptor therapy. Recent advances indicate that the widespread use of biomarkers may herald the next major advance in the diagnosis and management of CRC.

Impact of KRAS and BRAF Gene Mutation Status on Outcomes From the Phase III AGITG MAX Trial of Capecitabine Alone or in Combination With Bevacizumab and Mitomycin in Advanced Colorectal Cancer

Mutations affecting the KRAS gene are established predictive markers of outcome with anti-epithelial growth factor receptor (EGFR) antibodies in advanced colorectal cancer (CRC). The relevance of these markers for anti-vascular endothelial growth factor (VEGF) therapy is controversial. This analysis was performed to assess the predictive and prognostic impact of KRAS and BRAF gene mutation status in patients receiving capecitabine with bevacizumab (CG) or capecitabine without bevacizumab in the phase III AGITG MAX (Australasian Gastrointestinal Trials Group MAX) study. Mutation status was determined for 315 (66.9%) of the original 471 patients. Mutation status was correlated with efficacy outcomes (response rate, progression-free survival [PFS], and overall survival [OS]), and a predictive analyses was undertaken. Mutations in KRAS and BRAF genes were observed in 28.8% and 10.6% of patients, respectively. KRAS gene mutation status (wild type [WT] v mutated [MT]) had no prognostic impact for PFS (hazard ratio [HR], 0.89; CI, 0.69 to 1.14) or OS (HR, 0.97; CI, 0.73 to 1.28). BRAF mutation status (WT v MT) was not prognostic for PFS (HR, 0.80; CI, 0.54 to 1.18) but was prognostic for OS (HR, 0.49; CI, 0.33 to 0.73; P = .001). By using the comparison of capecitabine versus capecitabine and bevacizumab (CB) and CB plus mitomycin (CBM), KRAS gene mutation status was not predictive of the effectiveness of bevacizumab for PFS or OS (test for interaction P = .95 and 0.43, respectively). Similarly, BRAF gene mutation status was not predictive of the effectiveness of bevacizumab for PFS or OS (test for interaction P = .46 and 0.32, respectively). KRAS gene mutation status was neither prognostic for OS nor predictive of bevacizumab outcome in patients with advanced CRC. BRAF gene mutation status was prognostic for OS but was not predictive of outcome with bevacizumab.

Impact of KRAS and EGFR Gene Mutations on Recurrence and Survival in Patients with Surgically Resected Lung Adenocarcinomas

Oncogenic gene mutations observed in lung adenocarcinomas, such as epidermal growth factor receptor (EGFR) and KRAS, have some predictive value for chemotherapeutic drugs or EGFR-tyrosine kinase inhibitors. However, the influence of these gene alterations on patients' prognosis remains controversial. We retrospectively analyzed the tumors of 180 patients with completely resected pathological stage I-III lung adenocarcinoma which harbored either KRAS codon 12 mutation or EGFR gene mutations within exons 18-21 to investigate the impact of these gene mutations on the patients' survival. Gene mutations were detected by established methods. Of 180 patients, 32 had KRAS codon 12 mutations (KRAS group), 148 had EGFR mutations within exon 18-21 (EGFR group). Pathological stage and operation mode were independent factors for disease-free survival. However, the EGFR group had better overall survival than the KRAS group (P = 0.0271). Cox proportional hazard model revealed pathological stage (P = 0.0001) and presence of EGFR gene mutations (P = 0.0408) were independent factors for overall survival. In survival after tumor recurrence, the EGFR group had a better median survival time (46.7 months) after recurrence than the KRAS group (26.0 months). In patients with completely resected lung adenocarcinomas, KRAS and EGFR gene mutation status of tumors was not associated with disease-free survival. However, the presence of an EGFR gene mutation boded well for the patient's overall survival, and thus patients with EGFR mutations have a better prognosis than those with KRAS mutations.

Cetuximab Plus Capecitabine and Irinotecan Compared With Cetuximab Plus Capecitabine and Oxaliplatin As First-Line Treatment for Patients With Metastatic Colorectal Cancer: AIO KRK-0104—A Randomized Trial of the German AIO CRC Study Group

The AIO KRK-0104 randomized phase II trial investigated the efficacy and safety of cetuximab combined with capecitabine and irinotecan (CAPIRI) or capecitabine and oxaliplatin (CAPOX) in the first-line treatment of metastatic colorectal cancer (mCRC). A total of 185 patients with mCRC were randomly assigned to cetuximab (400 mg/m(2) day 1, followed by 250 mg/m(2) weekly) plus CAPIRI (irinotecan 200 mg/m(2), day 1; capecitabine 800 mg/m(2) twice daily days 1 through 14, every 3 weeks; or cetuximab plus CAPOX (oxaliplatin 130 mg/m(2) day 1; capecitabine 1,000 mg/m(2) twice daily day 1 through 14, every 3 weeks). The primary study end point was objective response rate (ORR). In the intention-to-treat patient population (n = 177), ORR was 46% (95% CI, 35 to 57) for CAPIRI plus cetuximab versus 48% (95% CI, 37 to 59) for CAPOX plus cetuximab. Analysis of the KRAS gene mutation status was performed in 81.4% of the intention to treat population. Patients with KRAS wild-type in the CAPIRI plus cetuximab arm showed an ORR of 50.0%, a PFS of 6.2 months and an OS of 21.1 months. In the CAPOX plus cetuximab arm, an ORR of 44.9%, a PFS of 7.1 months and an OS of 23.5 months were observed. While ORR and PFS were comparable in KRAS wild-type and mutant subgroups, a trend toward longer survival was associated with KRAS wild-type. Both regimens had manageable toxicity profiles and were safe. This randomized trial demonstrates that the addition of cetuximab to CAPIRI or CAPOX is effective and safe in first-line treatment of mCRC. In the analyzed regimens, ORR and PFS did not differ according to KRAS gene mutation status.

Schedule-dependent cytotoxic synergism of pemetrexed and erlotinib in BXPC-3 and PANC-1 human pancreatic cancer cells

Previous studies have shown that both pemetrexed, a cytotoxic drug, and erlotinib, an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), inhibit the cell growth of pancreatic cancer cells. However, whether they exert a synergistic antitumor effect on pancreatic cancer cells remains unknown. The present study aimed to assess the synergistic effect of erlotinib in combination with pemetrexed using different sequential administration schedules on the proliferation of human pancreatic cancer BXPC-3 and PANC-1 cells and to probe its cellular mechanism. The EGFR and K-ras gene mutation status was examined by quantitative PCR high-resolution melting (qPCR-HRM) analysis. BXPC-3 and PANC-1 cells were incubated with pemetrexed and erlotinib using different administration schedules. MTT assay was used to determine cytotoxicity, and cell cycle distribution was determined by flow cytometry. The expression and phosphorylation of EGFR, HER3, AKT and MET were determined using Western blotting. Both pemetrexed and erlotinib inhibited the proliferation of BXPC-3 and PANC-1 cells in a dose- and time-dependent manner in vitro. Synergistic effects on cell proliferation were observed when pemetrexed was used in combination with erlotinib. The degree of the synergistic effects depended on the administration sequence, which was most obvious when erlotinib was sequentially administered at 24-h interval following pemetrexed. Cell cycle studies revealed that pemetrexed induced S arrest and erlotinib induced G(0)/G(1) arrest. The sequential administration of erlotinib following pemetrexed induced S arrest. Western blot analyses showed that pemetrexed increased and erlotinib decreased the phosphorylation of EGFR, HER3 and AKT, respectively. However, both pemetrexed and erlotinib exerted no significant effects on the phosphorylation of c-MET. The phosphorylation of EGFR, HER3 and AKT was significantly suppressed by scheduled incubation with pemetrexed followed by erlotinib, but not by concomitant or sequential incubation with erlotinib followed by pemetrexed. In summary, our results demonstrated that the combined use of erlotinib and pemetrexed exhibited a strong synergism in BXPC-3 and PANC-1 cells. The inhibitory effects were strongest after sequential administration of pemetrexed followed by erlotinib. The synergistic effects may be related to activation of the EGFR/HER3/AKT pathway induced by pemetrexed.

Tumor biomarker analyses from the phase III ZODIAC study of docetaxel (D) plus or minus vandetanib (VAN) in second-line advanced NSCLC.

7516 Background: VAN is a once-daily oral inhibitor of VEGFR, EGFR, and RET signaling. VAN (100 mg/day) + D significantly prolonged PFS in ZODIAC, which included prospective exploratory analyses of potential relationships between clinical outcome and tumor biomarkers. Methods: Pts (n=1,391) with stage IIIB/IV NSCLC (mean age, 58 yrs; 30% female; any histology) were randomized to VAN + D or D + placebo (P). Prespecified analyses were performed on archival tumor samples (n=570) from consenting pts (n=958): EGFR protein expression by immunohistochemistry (IHC, n=362), EGFR gene copy number by fluorescent in situ hybridization (FISH, n=348), and EGFR (n=347) and KRAS (n=330) gene mutation status (wild-type [WT] or mutation [MT]) by the ARMS assay. Results: Baseline characteristics of pts with evaluable tumor samples were generally consistent with all pts. High EGFR protein expression (≥1% tumor cells stained, IHC+) was detected in 318 (88%) evaluable samples, 123 (35%) samples were FISH+ (defined as high EGFR gene polysomy or EGFR gene amplification), 50 (14%) samples had EGFR MT (exons 18–21), and 43 (13%) samples had KRAS MT (exons 12–13). Consistent trends toward improved PFS, overall survival and objective response rate for pts with EGFR FISH+ or EGFR MT tumors were seen with VAN + D vs D + P (Table). No consistent trends for differential benefits were associated with EGFR protein expression or KRAS mutation status. Conclusions: Exploratory analyses suggest that EGFR gene copy number (FISH+) and EGFR mutation status (EGFR MT) may have some predictive value in identifying pts who receive most benefit from VAN + D in second-line NSCLC. n PFS OS ORR HR, 97.58% CI HR, 97.52% CI HR, 97.5% CI All 1,391 0.79, 0.70–0.90 0.91, 0.78–1.07 1.84, 1.29–2.64 EGFR IHC+ 318 0.80, 0.61–1.04 0.77, 0.55–1.07 1.68, 0.84–3.39 IHC- 44 0.82, 0.38–1.79 1.08, 0.45–2.62 2.17, 0.30–15.85 FISH+ 123 0.61, 0.39–0.94 0.48, 0.28–0.84 3.90, 1.02–14.82 FISH- 225 1.20, 0.87–1.65 1.13, 0.78–1.64 1.20, 0.46–3.10 MT 50 0.51, 0.25–1.06 0.46, 0.14–1.57 3.34, 0.80–13.89 WT 297 0.99, 0.76–1.31 0.93, 0.67–1.28 0.98, 0.41–2.33 KRAS MT 43 1.04, 0.51–2.15 0.78, 0.35–1.75 1.81, 0.11–30.83 WT 287 0.75, 0.57–1.00 0.87, 0.61–1.22 1.88, 0.89–3.97 Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration AstraZeneca AstraZeneca AstraZeneca AstraZeneca Genzyme

Biomarkers for cetuximab-based neoadjuvant radiochemotherapy in advanced rectal cancer.

3563 Background: Recent phase II trials in locally advanced rectal cancer patients have shown that cetuximab-based neoadjuvant radiochemotherapy is feasible but without a significant improvement of clinical outcome. In order to identify a subgroup of patients with a marked benefit,we assessed gene expression of factors involved in tumor growth (EGFR), angiogenesis (VEGF, VEGFR1, VEGFR2d), DNA repair (ERCC1) and drug metabolism (TS) as well as KRAS gene mutation status to characterize molecular predictors for clinical outcome in locally advanced rectal cancer patients treated with preoperative cetuximab-based chemoradiation followed by surgery. Methods: 130 patients with locally advanced rectal cancer who were enrolled in phase II clinical trials treated with cetuximab-based chemoradiation in European cancer centers were included. Tumor tissue was obtained prior to neoadjuvant and after surgical therapy. Histomorphologic regression was defined using a modified Dworak regression system (grade 0/1: nonresponse; grade 4: complete response). After microdissection and extraction of the RNA/DNA, intratumoral gene expression levels and KRAS mutation status were analyzed. Results: Asignificantly decrease of TS, VEGFR1 and VEGFR2d expression was detected during neoadjuvant therapy (p < 0.02). High pre-therapeutic VEGF expression was significantly correlated with nonresponse (p = 0.033). KRAS mutations were found in 42 % of the patients. The mutation status (wild type [wt] vs. mutant [mt]) was significantly correlated with response: patients with a wt-status showed more frequently a complete response to neoadjuvant treatment (p = 0.025). In patients with a wt-status, high VEGF and EGFR mRNA expressions were significantly associated with complete response (p < 0.04). KRAS transversions (tv) vs. wt-status was also associated with tumor regression: nonresponse was more common in patients with KRAS tv (p = 0.007). Conclusions: This study suggests pretherapeutic intratumoral EGFR and VEGF mRNA expression as well as KRAS mutation status to be predictive markers for tumor response to neoadjuvant cetuximab-based chemoradiation of patients with locally advanced rectal cancer. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Response Genetics Bristol-Myers Squibb, ImClone Systems, Merck KG Response Genetics Bristol-Myers Squibb, ImClone Systems, Merck KG, Merck Serono, Roche, sanofi-aventis Merck, Roche, sanofi-aventis

Significance of K-ras detection in colorectal cancer

To determine the mutation status of K-ras gene in colorectal cancer and analyze the associations between its mutation status and clinicopathological characteristics in colorectal cancer so as to select the patients likely to benefit from a targeted therapy. A total of 208 colorectal cancer tissue samples were collected from September 2008 to February 2009. DNA was extracted with a genomic DNA miniprep kit. Then PCR was performed with the designed primers and the product directly sequenced by the Sanger method. Then the associations between K-ras mutation status and clinicopathological characteristics in colorectal cancer were analyzed. Of 208 cases, 91 cases of K-ras gene mutation were detected. The 12 or 13 codon had a mutation rate of 43.8%. There were no significant differences in gender, tumor location, histopathological grading and Duke's stage between the wild and mutated groups. Detection of K-ras gene status in colorectal cancer will help to select the patients likely to benefit from the monoclonal antibody therapy of targeting epidermal growth factor receptor.

Bevacizumab is beneficial for patients with metastatic colorectal cancer (MCC), regardless of KRAS gene mutation status,

Bevacizumab is beneficial for patients with metastatic colorectal cancer (MCC), regardless of KRAS gene mutation status,