KRAS Mutations In Codons Research Articles

Prognostic significance of KRAS and BRAF mutations in Japanese patients with colorectal cancer.

e14033 Background: Recent evidence highlights the potential prognostic and predictive value of BRAF and K-RAS gene alterations in patients with colorectal cancer. To determine whether differences exist in the molecular mechanisms driving colorectal cancer between Japanese and Western, we characterized Japanese patients with colorectal cancer by assessing genetic alterations involved in cancer progression and response to treatment. Methods: We retrospectively evaluated 254 Japanese diagnosed with colorectal cancer at our institution between 1994 and 2009. Mutations in KRAS codons 12 and 13 and BRAF codon 600 were identified by direct sequencing. Microsatellite instability (MSI) status was determined by genotyping in the 5 loci. Associations between KRAS or BRAF mutation and clinicopathological characteristics and prognosis were evaluated. Results: KRAS and BRAF mutation were detected in 33.5% and 6.7% of all patients, respectively. KRAS mutation was correlated with poor recurrence free survival (RFS) (p = 0.03), especially in stage II patients (p = 0.007). BRAF mutation was significantly correlated with the anatomical site of tumor (p < 0.001), tumor grade (p = 0.001) and high frequency of microsatellite instability (p < 0.001). BRAF mutation was also correlated with poor overall survival in all cases of patients (p = 0.009). Overall, the background of KRAS and BRAF mutation was almost similar between CRCs of Western countries and those of Japanese. However, KRAS mutation status was considered to be helpful to predict recurrence in Japanese patients with stage II CRC. Conclusions: Our findings indicate that BRAF and K-RAS mutation plays an important role in the tumorigenesis of colorectal cancer. These results indicate that molecular analysis for BRAF and K-RAS may be a useful biomarker for identifying patients with right-sided colon cancer with poor outcome who may benefit from a more individualized course of therapy.

Mutations in NRAS codon 61, KRAS codon 146, and BRAF V600E as prognostic factors in patients who received anti-EGFR antibody for metastatic colorectal cancer.

e14126 Background: Previous studies showed that gene mutations (NRAS, BRAF, PIK3CA) are associated with a poor prognosis or resistance of anti-EGFR antibody in metastatic colorectal cancer (mCRC) patients with wild type (WT) of KRAS codon 12/13 (KRAS-WT). However the significance of these biomarkers has not been clarified. In addition, EGFR immunohistochemistry (IHC) and EGFR gene amplification to evaluate the efficacy of anti-EGFR antibody treatment has not been reported for mCRC. Methods: We evaluated tumor response and survival in patients who received anti-EGFR antibody by mutation analysis of KRAS, NRAS, BRAF, and PIK3CA in KRAS-WT patients with mCRC. Tumor DNA samples are obtained from patients treated in our hospital with anti-EGFR antibody between August 2008 and August 2011. Results: A total of 117 patients were enrolled in this analysis, including 100 KRAS-WT patients. Seventy-one patients (60.7%) were all WT for KRAS, NRAS, BRAF, and PIK3CA, and 46 patients (39.3%) had at least 1 mutation or had insufficient DNA samples to analyze. Mutations of KRAS codon 61 (2 patients), KRAS codon 146 (5), BRAF V600E (2), PIK3CA exon9 (8), NRAS codon 12/13 (2), and NRAS codon 61 (5) were detected. No patients had a mutation of PIK3CA exon 20. Patients with at least 1 mutation had no response. Mutations of NRAS codon 61, KRAS codon 146, and BRAF V600E were associated with a shorter progression free survival (PFS) compared with all WT patients (p=0.049, p=0.004, p=0.036, respectively). Twelve patients (12% of KRAS-WT patients) with a mutation of NRAS codon 61, KRAS codon146, and BRAF V600E had poor prognosis compared with the other KRAS-WT patients (PFS, 6.4 vs 2.0 months, p<0.001; overall survival (OS), 13.7 vs 7.9 months, p=0.012). In all WT patients, moderate to strong EGFR IHC was associated with a better response rate than negative and weak IHC (p=0.046). Conclusions: Mutations of NRAS codon 61, KRAS codon 146, and BRAF V600E could be a strong prognostic factor of anti-EGFR antibody in patients with mCRC. Combination of IHC and DISH of EGFR could identify patients with a tumor response to anti-EGFR antibody in patients that are all WT for KRAS, NRAS, BRAF, and PIK3CA.

Abstract 2097: In situ mutation detection in cancer tissue sections for research and diagnostics in clinical oncology

Abstract Activating oncogenic mutations are targets for a new generation of cancer drugs. Current mutation assays for clinical diagnostics are based on DNA-extracts from tissue sections that often contain morphologically heterogeneous neoplastic regions with variable mixtures of normal stromal and inflammatory cells. We have developed an RNA-based in situ mutation assay that can target oncogenic mutations in a multiplex fashion on tissue slides by the use of multiple mutation-specific padlock probes and rolling-circle amplification. For EGFR therapy prediction, we demonstrate reliable in situ detection of KRAS mutations in codon 12 and 13 in colon and lung cancer - on cytologic tumor imprints as well as on fresh frozen and formalin-fixed, paraffin-embedded tissue sections. High throughput screening of KRAS mutation status was successfully performed on a tissue microarray. Moreover, we show how the pattern of expressed mutated and wild-type alleles can be studied in situ from tumors with complex combinations of mutated EGFR, KRAS and TP53. This in situ method holds great promise as a tool to investigate the role of somatic mutations during tumor progression and for prediction of response to targeted therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2097. doi:1538-7445.AM2012-2097

Abstract 5495: Does KRAS testing in metastatic colorectal cancer impact overall survival: A comparative effectiveness study in a population-based sample

Abstract The anti-epidermal growth factor (EGFR) monoclonal antibodies cetuximab and panitumumab are approved for the treatment of metastatic colorectal cancer (mCRC), but have been shown to be ineffective if the tumor has a mutation in KRAS codon 12 or 13. Comparative effectiveness research is intended to create evidence for decision making, and to find out “what works” in health care. This is especially important in scenarios like KRAS testing among patients with mCRC, since there is uncertainty around the significance of rarer mutations, and no proven alternative treatment for those who are found to harbor KRAS mutations in codons 12 or 13. We sought to determine whether recommendations for KRAS testing implemented in mid-2008 impacted survival in mCRC among 1203 mCRC patients from seven integrated health plans that are part of the Cancer Research Network. We included Stage IV cases diagnosed from 2006- 2009 and stage III cases initially diagnosed from 2004- 2008 who progressed to distant metastatic CRC (determined using chart review). We abstracted complete treatment data, pathology reports, survival data and KRAS testing results from electronic medical records. For cases that had not been previously tested for KRAS mutation status, we tested archived pathology specimens from the primary tumor. We used Kaplan-Meier plots and Cox proportional hazards models to examine whether overall survival differed among stage III and IV cases diagnosed before (n=751) and after (n=452) the implementation of KRAS testing. We included 918 stage IV cases and 285 stage III cases with progression. KRAS mutations (codon 12, 13, or 61) were found in 40% of tumors. Mutations were more common among tumors arising in the proximal compared to distal colon (46% mutated in ascending colon versus 33% in sigmoid colon). Median survival among stage III cases with progression was 589 days, compared to 437 days for stage IV cases (p=0.004). EGFR inhibitors were given to 26% of patients in the pre-recommendation period, and 13% of patients in the post-recommendation period. We found no survival differences by mutation status. We also found no statistically significant difference in survival time between the pre- and post- KRAS testing recommendations. Our data suggest that KRAS testing can be used to target anti-EGFR therapies without compromising overall survival time among mCRC patients in a usual care setting. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5495. doi:1538-7445.AM2012-5495

EGFR and KRAS Mutational Analysis and Their Correlation to Survival in Pancreatic and Periampullary Cancer

Pancreatic and periampullary cancers have a high incidence of activating KRAS mutations. The aim of this study was to determine the incidence of KRAS and EGFR mutations in pancreatic and periampullary cancers and their relationship with survival. One hundred patients undergoing pancreaticoduodenectomy or pancreatic biopsy for cancer were recruited. Samples of formalin-fixed paraffin-embedded or fresh pancreatic tissue were obtained. EGFR was analyzed by DNA sequencing of exons 18 to 21. KRAS was analyzed by pyrosequencing of codons 12, 13, and 61. EGFR mutations were found in 2 (2.3%) of 88 assessable cases. One in exon 18 (c.1966C>T, p.Q710X) and 1 in exon 19 (c.2066A>G, p.E734G). A synonymous single-nucleotide polymorphism in exon 20 (c.2361G>A, p.Q787) was identified in 57 (67.8%) of 84 patients studied. Twenty-eight (41.2%) of 68 cases harbored a point mutation in KRAS codon 12 (26 cases) and codon 61 (2 cases). The overall median survival was 308 days (range, 7-2623 days). The presence of KRAS point mutations did not significantly alter median survival time (22.8 vs 28.1 months, P = 0.88). EGFR somatic mutations are rare in pancreatobiliary malignancies. KRAS mutations are less common than previous reports and do not correlate with survival.

Mutant (MT) KRAS codon 12 and 13 alleles in patients (pts) with metastatic colorectal cancer (mCRC): Assessment as prognostic and predictive biomarkers of response to panitumumab (pmab).

383 Background: Pmab is a fully human monoclonal antibody against the epidermal growth factor receptor (EGFR). Significant improvement in progression-free survival (PFS) was demonstrated in pts with wild-type (WT) KRAS mCRC treated with pmab+FOLFOX4 (1st-line; study 20050203), pmab+FOLFIRI (2nd-line; study 20050181), and pmab monotherapy (study 20020408). In mCRC, mutations in KRAS codons 12 and 13 are established biomarkers for lack of clinical benefit to anti-EGFR therapies. We retrospectively examined individual MT KRAS codon 12 and 13 alleles as prognostic and predictive biomarkers of response in three phase 3 studies. Methods: Pts were randomized to receive FOLFOX4, FOLFIRI, or best supportive care +/- pmab 6.0 mg/kg Q2W in studies 20050203, 20050181, and 20020408, respectively. The MT KRAS codon 12 and 13 alleles (G12A, G12C, G12D, G12R, G12S, G12V, G13D) were detected using the Therascreen K-RAS Mutation Kit (Qiagen). Results: MT KRAS codon 12 and 13 alleles were detected in 40% (440/1096), 45% (486/1083), and 43% (184/427) of pts in studies 20050203, 20050181, and 20020408, respectively. MT KRAS allele distribution was conserved across studies and balanced between treatment arms. Baseline demographic and clinical features were comparable between all MT KRAS allele subgroups. Across all studies, no single MT KRAS allele was consistently prognostic for PFS or overall survival (OS) in the control arm-treated pts. Similarly, no single MT KRAS allele was a consistent positive or negative predictive factor for PFS or OS in pmab-treated pts. Only in the pmab+FOLFOX4 arm of study 20050203 were G13D (unfavorably) and G12V (favorably) significantly associated with OS. Response rates were similar between MT KRAS allele groups in the 1st- and 2nd-line mCRC treatment setting. Finally, in analyses of pts pooled from all 3 trials, only the G12A KRAS allele emerged as a significant negative predictive factor for OS. Conclusions: The lack of consistent results across three lines of therapy indicates pts with MT KRAS codon 12 or 13 alleles are unlikely to respond to pmab therapy. Currently, only pts with WT KRAS mCRC should be treated with pmab.

Cetuximab-related skin toxicity in metastatic colorectal cancer (mCRC) patients and its correlation with molecular markers: Results from the German AIO CRC 0104 trial.

491 Background: Skin toxicity is a frequent adverse event of EGFR targeting agents. The role of cetuximab induced skin toxicity (Cet-ST), for the most acneiform skin rash, as a prognostic or a predictive factor of treatment efficacy is currently under discussion. Methods: The prognostic and predictive value of Cet-ST in relation to treatment response and survival of patients of a randomized trial investigating CAPIRI plus cetuximab versus CAPOX plus cetuximab as first-line treatment of mCRC was analyzed. Cet-ST was grouped into clinically relevant (grade 2-3) and non relevant (grade 0-1) toxicity (NCI-CTCAE 3.0). KRAS mutations in codons 12 and 13, EGFR-FISH, EGFR-IHC and EGFR intron-1 polymorphism were evaluated in tumor specimens. Results: A total of 149 patients got cetuximab until the first tumor assessment (6 weeks) and were used for this analysis. Overall response rate was higher in patients with grade 2-3 Cet-ST when compared to grade 0-1 (62.1% vs. 41.3%). Patients without Cet-ST (grade 0) had a short PFS (1.9 months) and OS (11.0 months). PFS (7.8 months vs. 5.2 months) and OS (30.3 months vs. 18.0 months) were longer in patients with Cet-ST grade 2-3 than in patients with grade 0-1 Cet-ST. Almost 90% of Cet-ST occurred during the first two cycles of treatment. When only KRAS codon-12 mutated tumors which are thought not to be sensitive to cetuximab were investigated, Kaplan-Meier differences in PFS and OS times between patients with grade 0-1 Cet-ST and grade 2-3 Cet-ST became statistically significant. In a multivariate analysis, male gender, age and EGFR intron-1 polymorphism were significantly correlated with Cet-ST. Conclusions: Cetuximab related skin toxicity is a strong predictor of outcome. It is proposed that Cet-ST is rather a prognostic than a predictive factor since this effect is most evident in patients with KRAS codon-12 mutated tumors. EGFR intron-1 polymorphism appears to be a predictor of Cet-ST.

Association of KRAS G12D mutation with outcome in patients with pancreatic cancer after surgery.

221 Background: The frequency of KRAS gene mutations in pancreatic adenocarcinoma is high and most mutations occur in codon 12 and 13. However, the association of KRAS mutation status with clinical outcome of pancreatic cancer patients after surgery is not clearly understood. The aim of present study was to clarify whether presence of mutation in KRAS is of prognostic significance, and to determine whether the different type of KRAS mutation have different impact on clinical outcome in pancreatic cancer. Methods: A total of 62 pancreatic adenocarcinoma tissues from patients underwent curative surgery were analyzed for KRAS mutation. DNA was extracted from the tissue microarray. The domain containing the KRAS gene codons 12 and 13 was amplified by PCR, and KRAS mutation was detected by loop hybrid mobility shift assay (LH-MSA). Results: KRAS mutation was detected in 41 of 62 tumors (66.1%). Mutations of KRAS codon 12 and codon 13 were detected in 37 of 62 tumors (59.7%) and in 4 of 62 tumors (6.5%), respectively. G12D mutation were detected in 35.5% (22/62) and G12V mutation in 19.4% (12/62) of all. The patients with KRAS mutations had a significantly shorter overall survival (OS) (log rank, p=0.0375) and disease free survival (DFS) (p=0.0175). When the type of mutation were evaluated, G12D mutation was significantly associated with both shorter OS (p=0.0410) and DFS (p=0.0214), whereas G12V mutation was associated with neither OS (p=0.6727) nor DFS (p=0.9854). Conclusions: The presence of KRAS mutation was significantly associated with poor outcome of pancreatic cancer patients after surgery. A specific mutation G12D demonstrated significant association with shorter OS and DFS in pancreatic cancer. The different type of KRAS mutation might have different impact on clinical outcome in pancreatic cancer.

Molecular Analysis of Colorectal Tumors within a Diverse Patient Cohort at a Single Institution

African American colorectal cancer patients have worse survival outcomes than Caucasian patients. To determine whether differences exist in the molecular mechanisms driving colorectal cancer between African Americans and Caucasians, we characterized patient tumors from a single institution by assessing genetic alterations involved in colorectal cancer progression and response to treatment. We retrospectively examined 448 African Americans and Caucasians diagnosed with colorectal cancer at The University of Chicago Medical Center between 1992 and 2002. Microsatellite instability (MSI) status was determined by genotyping the BAT25, BAT26, BAT40, D5S346, and BAX loci. Mutations in KRAS codons 12 and 13 and BRAF codon 600 were identified by direct sequencing. MSI and detected mutations were correlated with clinicopathologic features. Overall, no difference existed in MSI or BRAF mutation frequencies between African Americans and Caucasians. However, African Americans with microsatellite stable (MSS)/MSI-low (MSI-L) tumors had a higher proportion of KRAS mutations than Caucasians (34% vs. 23%, P = 0.048) that was isolated to proximal colon cancers and primarily driven by mutations in codon 13. There was no racial difference in receipt of chemotherapy, but African Americans with MSS/MSI-L tumors had a 73% increased risk of death over Caucasians that could not be explained by known prognostic factors. The significantly higher risk of death among African Americans with MSS/MSI-L tumors may be related to differences in the distribution of factors influencing response to standard therapies. These data underscore the need for further research into the molecular mechanisms driving colorectal cancer progression in underserved and understudied populations.

The frequency and spectrum of K-ras mutations among Iraqi patients with sporadic colorectal carcinoma

The epidemiology of colorectal cancers (CRC) is well known to differ in different geographical regions. K-ras mutations have been implicated in CRC carcinogenesis and they were extensively studied in developed countries; however, such studies are scarce from developing countries, like Iraq. To determine the frequency and spectrum of K-ras mutations among CRC Iraqi patients, and their clinico-pathological associations, if any. Fifty consecutive surgically resected sporadic CRC were evaluated. The evaluation included screening for ten K-ras mutations in codon 12 and 13 by mutant enriched polymerase chain reaction followed by reverse hybridization to oligospecific probes. Out of the 50 enrolled patients, 24 (48%) had K-ras mutations. A total of 29 mutations were identified in the tumors of the latter 24 patients (20/24 tumors had single mutations, 3/24 had double mutations and 1/24 had triple mutations). The most frequently encountered mutations were the G>T transversions and G>A transitions (41.4% each). Codon 12 mutations constituted 89.7%, while codon 13 the remaining 10.3%. The most frequent mutation was GGT>GTT (Gly>Val) of codon 12 documented in 31%. No significant clinico-pathological correlations with K-ras mutational status were identified. The K-ras mutations are frequently encountered among Iraqi sporadic CRC patients, with relative higher frequencies of G>T transversions and Gly>Val codon 12 substitutions than encountered in their counterparts in developed countries. The latter is most likely to be related to differences in local carcinogens exposure, an aspect which requires further scrutiny.

K-ras mutations are correlated to lymph node metastasis and tumor stage, but not to the growth pattern of colon carcinoma

In colorectal carcinoma, pathological assessment of tumors is essential for determining therapy and prognosis of the disease. Molecular associations of tumor complexity index and genetic alternations can be helpful to understand the tumor progression mechanism. Oncogenic K-ras is one of the major colorectal cancer associated genes, and is mutated in up to 50% of colorectal cancers. In this current study, we correlated tumor complexity index with mutations in K-ras codon 12, 13, and 61 in association with different clinicopathological parameters such as TNM stage, localization, sex, and age. Formalin-fixed paraffin embedded tissue blocks from colon cancer samples was selected from 88 patients diagnosed with adenocarcinoma. Mutations in the K-ras gene were detected using pyrosequencing technique. Tumor complexity index was calculated using immunohistochemically stained images of the tumor outline of the specimens and then analyzing these pictures using Photoshop CS, Fovea Pro, and Image J computer programs. Statistical analysis was performed with SPSS. K-ras mutations were detected in 17 (19.3%) colon cancer samples. Most of the samples were at a lower complexity index. No correlation was observed between K-ras mutations and complexity index. However, K-ras mutations were correlated with regional lymph node metastasis and tumor stages and complexity index with tumor wall penetration. In conclusion, complexity index and K-ras mutations are independent events; however, both correlate with tumor progression and are important in the biologic development of colon carcinoma.

Analytical performance of a PCR assay for the detection of KRAS mutations (codons 12/13 and 61) in formalin-fixed paraffin-embedded tissue samples of colorectal carcinoma

KRAS mutation testing is mandatory before prescribing anti-epidermal growth factor monoclonal antibodies in the treatment of advanced colorectal cancer. We describe the performance of a TaqMelt polymerase chain reaction (PCR) assay—the cobas® KRAS Mutation Test—designed to detect 19 mutations in codons 12, 13, and 61. The limit of detection was determined using DNA blends from cell lines, plasmids, and formalin-fixed paraffin-embedded tissue specimens. Assay performance was compared to Sanger sequencing using a panel of 188 specimens. Discordant specimens were subjected to next generation pyrosequencing (454). Assay repeatability was assessed using a panel of six specimens. A >95% correct mutation call rate was obtained in all specimen types with ~5% mutant alleles at DNA inputs of 0.8–6.3 ng per PCR reaction; 100% detection rate was observed at the recommended DNA input of 50 ng. The positive percent agreement with Sanger was 97.5% (79/81) for codons 12/13 and 85.7% (6/7) for codon 61. Negative percent agreement was 94.4% (101/107) for codon 12/13 and 99.4% (180/181) for codon 61. Nine of 10 discordant specimens yielded 454 results consistent with the cobas® results. With repeated testing, the assay showed a correct call rate of 100% (192/192) for all operators, instruments, reagent lots, and days tested. The cobas® test detects KRAS mutations in codons 12, 13, and 61 at a limit of detection of <5%. The PCR assay was more sensitive and specific than Sanger sequencing, and performance was highly reproducible. Test performance was not influenced by various endogenous interfering substances or common gut microbes.

Is KRAS Mutation Associated with Interval Colorectal Cancers?

Colorectal cancers diagnosed in the interval after a complete colonoscopy may occur due to rapid tumor growth. Interval colorectal cancers are associated with microsatellite instability (MSI). Our aim was to study the association of KRAS mutation with interval colorectal cancers and MSI. We searched our institution's cancer registry for interval colorectal cancers, defined as colorectal cancers that developed within 5 years of a complete colonoscopy. These were frequency matched to patients with non-interval colorectal cancers. Archived cancer specimens were evaluated for KRAS mutations in codons 12 and 13 using sequencing, and MSI by sequencing microsatellite loci. Multivariable logistic regression was used to analyze the association between KRAS mutation status, MSI status and interval colorectal cancers. There were 63 interval and 131 non-interval colorectal cancers. KRAS mutation was present in 12.9% of interval cancers compared to 28.9% of non-interval cancers (P = 0.03). In multivariable logistic regression model, KRAS was inversely associated with interval cancers (OR 0.36; 95% CI 0.15-0.90). In Cox proportional hazards model, adjusting for age, tumor grade, TNM Stage and MSI status, we found no association between KRAS mutation and 5-year survival compared to cancers without KRAS mutation (HR 0.84; 95% CI 0.4-1.46; P = 0.5). KRAS mutation is inversely associated with interval cancers and with MSI, suggesting that it is a marker of the chromosomal instability pathway associated with slow tumor growth, and distinct from MSI rapidly growing cancers. Molecular characterization of colorectal cancers is helpful in determining underlying pathway and may determine therapy.

Abstract B161: PIK3CA mutations H1047R are associated with response to PI3K/AKT/mTOR signaling pathway inhibitors in early-phase clinical trials.

Abstract Background: Activating mutations in the PIK3CA gene have been identified in many malignancies. Preclinical and early clinical data suggest that these mutations predict response to PI3K/AKT/mTOR inhibitors in subsets of patients. Sensitivity and resistance mutation have not been reported to date. Methods: Patients with diverse cancers referred to the Phase I Clinical Trials Program for targeted therapy starting from October 2008 were analyzed for PIK3CA, and if, possible for KRAS mutations using PCR-based DNA sequencing. Patients with any tumor type and any PIK3CA mutation were treated whenever possible with agents targeting the PI3K/AKT/mTOR signaling pathway. Treatment outcomes with respect to mutation types were analyzed. Results: Overall, 1012 patients were tested and 105 (10%) had PIK3CA mutations. Of the 105 patients with PIK3CA mutations, 66 (median number of prior therapies, 3) were treated on a protocol that included a PI3K/AKT/mTOR pathway inhibitor. Of these 66 patients, 11 (17%) achieved a partial response (PR) and 4 (6%) stable disease ≥ 6 months (SD≥6). The total of SD≥6/PR was 15 (23%). Patients with PIK3CA H1047R mutation (n=16) compared to patients with other PIK3CA mutations (n=50) had higher PR rate (6/16, 37.5% vs. 5/50, 10%; p=0.018), higher rate of SD≥6/PR (7/16, 44% vs. 8/50, 16%; p=0.037), and trend toward longer median progression-free survival (PFS) (5.7 months, 95%CI 0.4–11.0 vs. 2.0 months, 95%CI 1.8–2.2; p=0.064). Patients with a PIK3CA E542K mutation (n=11) compared to others (n=55) trended toward a worse median PFS (1.8 months, 95%CI 1.4–2.2 vs. 2.6 months, 95%CI 1.4–3.8; p=0.058). Of the 66 treated patients with PIK3CA mutations, 55 (83%) had enough tissue for KRAS testing. None of the 16 patients with PIK3CA and simultaneous KRAS mutations in codon 12 or 13 had a PR (0/16, 0% vs. 9/39, 23%; p=0.046) or SD≥6/PR (0/16, 0% vs. 13/39, 33.3%; p=0.011) as compared to patients with PIK3CA, but not KRAS codon 12 or 13 mutations, whereas 2 of 2 (100%) patients with PIK3CA and Q61H KRAS mutation in codon 61 had SD≥6 (n=1) and PR (n=1). Conclusion: Despite the small number of patients, our data suggest that PIK3CA mutations H1047R are associated with response to PI3K/AKT/mTOR inhibitors, whereas codon 12 and 13, but not codon 61 KRAS mutations are associated with resistance. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B161.

Clinical characterization of patients with metastatic colorectal cancer depending on the KRAS status

This retrospective study investigated the clinical characteristics of patients with metastatic colorectal cancer (mCRC) depending on the KRAS status, thereby differentiating KRAS exon 2 mutations in codon 12 versus codon 13. In total, 273 patients with mCRC receiving first-line therapy were analyzed. One hundred patients were treated within the FIRE-3 trial (FOLFIRI plus cetuximab or bevacizumab), 147 patients within the AIO KRK-0104 trial (cetuximab plus CAPIRI or CAPOX), and further 26 patients received therapy outside the study. Thirty-eight tumors with KRAS mutation in codon 13, 140 tumors with mutation in codon 12, and 95 tumors with KRAS wild type as a comparison were included in this analysis. Bivariate analyses demonstrated significant differences between KRAS wild-type, codon 12-mutated, and codon 13-mutated tumors with regard to synchronous lymph node metastasis (P=0.018), organ metastasis (76.8% vs. 65.9% vs. 89.5%, P=0.009), liver metastasis (89.5% vs. 78.2% vs. 92.1%, P=0.025), lung metastasis (29.5% vs. 42.9% vs. 50%, P=0.041), liver-only metastasis (48.4% vs. 28.8% vs. 28.9%, P=0.006), and metastases in two or more organs (49.5, 61.4, 71.1, P=0.047). Regression models indicated a significant impact of KRAS mutations in codon 12 versus codon 13 for synchronous organ and nodal metastasis (P=0.01, 0.03). This pooled analysis indicates that mCRC is a heterogeneous disease, which seems to be defined by KRAS mutations of the tumor. Compared with KRAS codon 12 mutations, codon 13-mutated mCRC presents as a more aggressive disease frequently associated with local and distant metastases at first diagnosis.

KRAS Mutation in Metastatic Pancreatic Ductal Adenocarcinoma: Results of a Multicenter Phase II Study Evaluating Efficacy of Cetuximab plus Gemcitabine/Oxaliplatin (GEMOXCET) in First-Line Therapy

Background: Genetic alterations within the epidermal growth factor receptor (EGFR) pathway, including KRAS mutations, have been demonstrated to be associated with response to EGFR inhibitors like cetuximab in colorectal cancers. Mutations in the KRAS gene have been found in 70–90% of pancreatic cancers. Unfortunately, the addition of cetuximab to chemotherapy did not increase response or survival in patients with advanced pancreatic cancer in phase II and phase III studies. The aim of this study was to evaluate the relationship between KRAS mutations and response or survival in patients with metastatic pancreatic cancer treated with cetuximab plus chemotherapy. Methods: Within a multicenter phase II trial, 64 patients with metastatic pancreatic cancer were treated with cetuximab in combination with gemcitabine and oxaliplatin until disease progression. Analyses of the EGFR pathway, including KRAS mutations, could be performed in 25 patients. Analyses were carried out following microdissection of the tumor. Results: Fourteen (56%) of the 25 patients examined harbored a point mutation in codon 12 of the KRAS gene. No differences between the groups were noted in median progression-free survival (104 days in KRAS wild-type patients vs. 118 days in patients with KRAS mutations). Overall survival was longer in wild-type patients compared to patients with KRAS mutations (263 vs. 162 days), but the difference did not reach statistical significance. A further analysis of our clinical phase II trial showed that the presence of a rash was significantly correlated with overall survival. Conclusions: KRAS mutation in codon 12 may be associated with reduced survival compared to KRAS wild type. The role of KRAS mutations for cetuximab therapy in pancreatic cancer warrants further investigation in larger trials to exclude an epiphenomenon. Furthermore, the development of a rash is indicative of clinical benefit.

Tumor-infiltrating lymphocytes and dendritic cells in human colorectal cancer: Their relationship to KRAS mutational status and disease recurrence

The prognosis of newly diagnosed colorectal cancer patients relies mostly on tumor-node metastasis classification. However, analyses of tumor-infiltrating lymphocytes and several molecular markers have also shown promising prognostic value. Mutations in the proto-oncogene KRAS, which occur early in colorectal carcinogenesis, have been demonstrated to be common in human colorectal cancer (CRC); however, their prognostic significance remains controversial. We examined the correlations between KRAS mutational status and tumor-infiltrating immune cells with respect to CRC recurrence. Mutations in KRAS were identified in 45.5% of the primary carcinomas in our cohort of patients: 65% in codon 12 and 35% in codon 13. Although codon 13 KRAS mutations were associated with disease relapse, they were present in both disease-free and relapsed patients. However, disease-free and relapsed patients differed markedly in their patterns of tumor-infiltrating immune cells. There was a trend toward decreased density of tumor-infiltrating lymphocytes (TILs) within the group of relapsed cases. In addition, relapsed patients with codon 13 mutations had markedly lower levels of tumor-infiltrating mature DC-LAMP(+) dendritic cells (DCs) and higher frequency of CD1a(+) cells compared with disease-free patients. Our data suggest that CRC patients with low levels of TILs, a high CD1a(+)/DC-LAMP(+) tumor-infiltrating DC ratio, and a KRAS mutation in codon 13 are at a high risk of disease recurrence.

Canadian Expert Group Consensus Recommendations: KRAS Testing in Colorectal Cancer

Monoclonal antibodies against the epidermal growth factor receptor (anti-egfr) when used in the treatment of metastatic colorectal cancer are associated with improved survival. Patients whose tumours harbor a KRAS mutation in codon 12 or 13 have been shown not to benefit from anti-egfr antibodies. The importance of KRAS mutation status in the management of patients with metastatic colorectal cancer has led to the elaboration of Canadian consensus recommendations on KRAS testing, with the aim of standardizing practice across Canada and reconciling testing access with the clinical demand for testing. The present guidelines were developed at a Canadian consensus meeting held in Montreal in April 2010. The best available evidence and expertise were used to develop recommendations for various aspects of KRAS testing, including indications and timing for testing, sample requirements, recommendations for reporting requirements, and acceptable turnaround times.

Differential detection of KRAS mutations in codons 12 and 13 with a modified loop-hybrid (LH) mobility shift assay using an insert-type LH-generator

BackgroundThe loop-hybrid mobility shift assay (LH-MSA) was previously developed for the rapid detection of the EGFR mutation L858R for predicting clinical responses to gefitinib in lung cancer. Recently, clinical importance of determining KRAS mutations has been demonstrated in colorectal tumors as tumors harboring mutated KRAS genes were not responsive to therapy with EGFR-targeted antibodies such as cetuximab. MethodsWe developed a new version of the LH-MSA using an insert-type LH generator that was capable of detecting all 12 KRAS mutations in codons 12 and 13. ResultsFeasibility evaluation was performed with this new LH-MSA on 215 colorectal cancer specimens. KRAS codon 12 mutations were detected in 23% specimens and codon 13 mutations in 6.5% specimens by LH-MSA at a rate better than by direct sequencing. ConclusionsUsing the new method, the G13D mutation was readily distinguishable from other KRAS mutations in codon 12 and, therefore, would be advantageous for clinical applications.

Gastric cancer and concomitant renal cancer: A systematic immunohistochemical and molecular analysis

The frequency of gastric cancer in patients with renal cell carcinoma (RCC) is exceptionally high in our region suggesting a common molecular basis. Our study aimed to characterize tumors and to analyze possible underlying molecular features in 12 patients with gastric cancer and concomitant RCC. We performed an immunohistochemical analysis including p53 protein expression, proliferative activity (MIB-1), mismatch repair status (hMLH1, hMSH2, hMSH6, PMS2) and E-cadherin expression in gastric cancers, which were additionally analyzed for Epstein-Barr-Encoded-RNA (EBER) by insitu hybridization. Microsatellite instability was analyzed with a PCR multiplex system and capillary electrophoresis. KRAS mutations in codons 12 and 13 were tested by pyrosequencing. All patients had clear cell RCCs, 10 of which were well differentiated and diagnosed in an early stage, while the gastric cancers of these patients were generally poorly or undifferentiated and diagnosed in an advanced stage. Gastric cancers showed reduced E‑cadherin staining in 10 out of 12 cases. Two gastric cancers demonstrated loss of hMLH1 and PMS2, which was confirmed by molecular analysis showing a high degree of microsatellite instability. All RCCs were microsatellite stable. KRAS mutation was detected in one of the two instable gastric cancers, while none of the RCCs had KRAS mutations. Another gastric cancer was positive for EBV. In conclusion, a coherent cause for gastric cancer and concomitant RCC, such as Lynch syndrome, a prominent role of KRAS mutation or EBV infection, was not found in our series. Other factors leading to a higher susceptibility for cancer must be explored to explain why individuals with RCC have a higher risk of developing gastric cancer in our region.