KRAS Mutations In cfDNA Research Articles

Novel diagnostic biomarkers for pancreatic cancer: assessing methylation status with epigenetic-specific peptide nucleic acid and KRAS mutation in cell-free DNA.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive tumor with a poor prognosis that poses challenges for diagnosis using traditional tissue-based techniques. DNA methylation alterations have emerged as potential and promising biomarkers for PDAC. In this study, we aimed to assess the diagnostic potential of a novel DNA methylation assay based on epigenetic-specific peptide nucleic acid (Epi-sPNA) in both tissue and plasma samples for detecting PDAC. The study involved 46 patients with PDAC who underwent surgical resection. Epi-TOP pancreatic assay was used to detect PDAC-specific epigenetic biomarkers. The Epi-sPNA allowed accurate and rapid methylation analysis without bisulfite sample processing. Genomic DNA extracted from paired normal pancreatic and PDAC tissues was used to assess the diagnostic efficacy of epigenetic biomarkers for PDAC. Subsequent validation was conducted on cell-free DNA (cfDNA) extracted from plasma samples, with 10 individuals represented in each group: PDAC, benign pancreatic cystic neoplasm, and healthy control. The combination of seven epigenetic biomarkers (HOXA9, TWIST, WT1, RPRM, BMP3, NPTX2, and BNC1) achieved 93.5% sensitivity and 96.7% specificity in discerning normal pancreatic from PDAC tissues. Plasma cfDNA, analyzed using these markers and KRAS mutations, exhibited a substantial 90.0% sensitivity, 95.0% specificity, and an overall 93.3% accuracy for discriminating PDAC. Notably, cancer antigen 19-9 and carcinoembryonic antigen both had an accuracy of 90.0%. Our study suggests that analyzing seven differentially methylated genes with KRAS mutations in cfDNA using the novel Epi-TOP pancreatic assay is a potential blood-based biomarker for the diagnosis of PDAC.

1637P Early retention of KRAS mutations in cfDNA is an ominous sign for pancreatic cancer patients during chemotherapy: A prospective cohort study

1637P Early retention of KRAS mutations in cfDNA is an ominous sign for pancreatic cancer patients during chemotherapy: A prospective cohort study

Abstract 5152: Mutation-agnostic detection of colorectal cancer-specific cell-free DNA using targeted methylation sequencing

Abstract BACKGROUND: Tumor-specific methylation changes in DNA CpG sites commonly occur in cancer and are believed to drive oncogenesis through gene silencing. Detection of methylation changes in circulating cell-free DNA (cfDNA) can offer a novel approach for cancer diagnostics. METHODS: Plasma samples from healthy controls and from patients with advanced colorectal and non-colorectal cancers were included in the study. Bisulfite conversion of cfDNA extracted from plasma was performed using EZ DNA Methylation Lightning Kit (Zymo Research) and was followed by library preparation using Accel-NGS Methyl-Seq DNA Library Kit (Swift Biosciences) and target enrichment using xGen Hybridization Capture for NGS Kit (IDT). Targeted methylation sequencing was done using NextSeq500 mid-output flow cell (300 cycles) (Illumina). Detection rates of methylation ratios in colorectal cancer samples were compared to non-colorectal cancers and healthy controls. RESULTS: First, we reviewed methylation changes in nearly 9,000 CpG sites in colorectal cancer (through TCGA database) and healthy controls. Subsequently, 32 CpG sites with greater than 50% methylation ratio in colorectal cancer and less than 1% methylation ratio in healthy controls were selected to develop targeted methylation sequencing based cfDNA assay. The assay was performed in 32 plasma samples from 20 individuals with advanced colorectal cancer who had tumor KRAS mutation, 8 individuals with advanced non-colorectal cancer who had tumor KRAS mutation (ovarian, n=2; endometrial, n=2; pancreatic, n=2; and lung cancer, n=2), and 4 healthy controls. Colorectal cancer specific methylation changes in cfDNA were detected in 85% (17/20) of colorectal cancer patients with a specificity of 92%. In colorectal cancer patients with confirmed KRAS mutation in cfDNA, methylation changes were detected in 92% (11/12) in comparison to 75% (6/8) in colorectal cancer patients without KRAS mutation in cfDNA. Median methylation ratio for target CpG sites was higher in colorectal cancer patients compared to patients with non-colorectal cancers and healthy controls (p<0.001). In 17 colorectal cancer patients with plasma samples collected before initiation of systemic cancer therapy, detection of methylation changes in cfDNA was associated with a shorter median progression-free survival compared to no detection (PFS; 8 weeks versus 54 weeks; p=0.027). CONCLUSIONS: Targeted methylation sequencing of cfDNA demonstrated high sensitivity and specificity for detection of colorectal cancer-specific cfDNA. Colorectal cancer patients with methylated cfDNA had shorter PFS while on cancer therapy. Citation Format: Mohamed A. Gouda, Dzifa Y. Duose, Morten Lapin, Stephanie Zalles, Helen J. Huang, Yuanxin Xi, Xiaofeng Zheng, Amira I. Aldesoky, Alshimaa M. Alhanafy, Mohamed A. Shehata, Jing Wang, Scott Kopetz, Funda Meric-Bernstam, Ignacio I. Wistuba, Rajyalakshmi Luthra, Filip Janku. Mutation-agnostic detection of colorectal cancer-specific cell-free DNA using targeted methylation sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5152.

Detection of Low-Frequency KRAS Mutations in cfDNA From EGFR-Mutated NSCLC Patients After First-Line EGFR Tyrosine Kinase Inhibitors.

BackgroundMolecular profiling of advanced EGFR mutated NSCLC has recently demonstrated the co-existence of multiple genetic alterations. Specifically, co-existing KRAS-mutations in EGFR NSCLCs have been described, despite their prevalence at progression and their role in the response to EGFR tyrosine kinase inhibitors (TKIs) remain marginally explored. Aim of our study was to investigate the prevalence of co-existing KRAS mutations at the time of progressive disease and explore their impact on clinical outcome.Materials and MethodsWe retrospectively analyzed by digital droplet PCR prevalence of KRAS co-mutations in 106 plasma samples of EGFR mutated NSCLC patients, in progressive disease after EGFR TKI treatment as first-line therapy.Results KRAS co-mutations (codon 12 and 13) were identified in 3 patients (2.8% of analyzed samples), with low allelic frequency (<0.2%), and had a negative impact on clinical outcome to first-line EGFR TKI.ConclusionDetection of KRAS mutations in cell-free DNA of EGFR mutant NSCLC patients at progression after first or second generation EGFR TKI is a rare event. Due to their low abundance, the negative impact of KRAS mutations on the response to EGFR TKI remains to be confirmed in larger studies.

Early assessment of KRAS mutation in cfDNA correlates with risk of progression and death in advanced non-small-cell lung cancer

BackgroundLiquid biopsy has the potential to monitor biological effects of treatment. KRAS represents the most commonly mutated oncogene in Caucasian non-small-cell lung cancer (NSCLC). The aim of this study was to explore association of dynamic plasma KRAS genotyping with outcome in advanced NSCLC patients.MethodsAdvanced NSCLC patients were prospectively enrolled. Plasma samples were collected at baseline (T1), after 3 or 4 weeks, according to treatment schedule (T2) and at first radiological restaging (T3). Patients carrying KRAS mutation in tissue were analysed in plasma with droplet digital PCR. Semi-quantitative index of fractional abundance of mutated allele (MAFA) was used.ResultsKRAS-mutated cohort included 58 patients, and overall 73 treatments (N = 39 chemotherapy and N = 34 immune checkpoint inhibitors) were followed with longitudinal liquid biopsy. Sensitivity of KRAS detection in plasma at baseline was 48.3% (95% confidence interval (CI): 35.0–61.8). KRAS mutation at T2 was associated with increased probability of experiencing progressive disease as best radiological response (adjusted odds ratio: 7.3; 95% CI: 2.1–25.0, p = 0.0016). Increased MAFA (T1–T2) predicted shorter progression-free survival (adjusted hazard ratio (HR): 2.1; 95% CI: 1.2–3.8, p = 0.0142) and overall survival (adjusted HR: 3.2; 95% CI: 1.2–8.4, p = 0.0168).ConclusionsLongitudinal analysis of plasma KRAS mutations correlated with outcome: its early assessment during treatment has great potentialities for monitoring treatment outcome in NSCLC patients.

The diagnostic accuracy of circulating free DNA for the detection of KRAS mutation status in colorectal cancer: A meta-analysis.

KRAS mutations have been reported as a reliable biomarker for epidermal growth factor receptor (EGFR) targeted therapy and are also associated with poor prognosis in colorectal cancer (CRC) patients. However, limitations of detecting KRAS mutations in tissues are obvious. KRAS mutations in the peripheral blood can be detected as an alternative to tissue analysis. The objective of this meta‐analysis was to evaluate the diagnostic value of cfDNA (circulating free DNA) compared with tissues and to investigate the prognostic potential of cfDNA KRAS mutations in CRC patients. Searches were performed in PubMed, Embase, and Cochrane Library for published studies. We extracted true‐positive (TP), false‐positive (FP), false‐negative (FN), true‐negative (TN) values, survival rate of CRC patients with mutant and wild‐type KRAS and calculated pooled sensitivity and specificity, positive/negative likelihood ratios [PLRs/NLRs], diagnostic odds ratios [DORs], and corresponding 95% confidence intervals [95% CIs]. We also generated a summary receiver operating characteristic (SROC) curve to evaluate the overall diagnostic potential. Totally, 31 relevant studies were recruited and used for the meta‐analysis on the efficacy of cfDNA testing in detecting KRAS mutations. The pooled sensitivity, specificity, PLR, NLR, and DOR were 0.637 (95% CI: 0.607‐0.666), 0.943 (95% CI: 0.930‐0.954), 10.024 (95% CI: 6.912‐14.535), 0.347 (95% CI: 0.269‐0.447), and 37.882 (95% CI: 22.473‐63.857), respectively. The area under the SROC curve was 0.9392. Together, the results suggest that detecting KRAS mutations in cfDNA has adequate diagnostic efficacy in terms of specificity. There is a promising role for cfDNA in the detection of KRAS mutations in CRC patients. However, prospective studies with larger patient cohorts are still required before definitive conclusions of the prognostic potential of cfDNA KRAS mutations in CRC patients were drawn.

Highlights of This Issue

Venetoclax, an oral BCL-2 inhibitor, is approved for treatment of patients with previously-treated chronic lymphocytic leukemia (CLL). With increased use of venetoclax in clinical practice, Davids and colleagues report on a comprehensive safety analysis of venetoclax monotherapy at the approved 400 mg daily dose in 350 patients enrolled in three phase-I or -II studies. The most common toxicities of venetoclax in relapsed/refractory CLL were mild gastrointestinal symptoms and transient, uncomplicated neutropenia. Tumor lysis syndrome at initiation was observed in some of the initial patients, but this risk was subsequently mitigated by risk-adapted prophylaxis, monitoring and stepwise dose ramp-up to 400 mg/day. Long-term continuous therapy with venetoclax was generally well-tolerated in patients with relapsed/refractory CLL when initiated with the current treatment algorithm. This study will help to inform the optimal management of CLL patients receiving venetoclax.Taselisib is a potent and selective PI3K inhibitor with greater efficacy against mutant versus wild-type phosphatidylinositol-4,5bisphosphate 3-kinase, catalytic subunit-alpha (PIK3CA). Inhibition of PI3K signaling in HR-positive breast cancer results in upregulation of estrogen receptor (ER)-dependent function. The combination of PI3K inhibition and ER inhibition with fulvestrant produces marked tumor regression in breast cancer models, providing a rationale for dual PI3K and ER inhibition in breast cancer. In this phase II trial, Dickler and colleagues evaluated the safety and efficacy of oral taselisib plus intramuscular injections of fulvestrant in women with advanced HR-positive breast cancer. The adverse event profile was typical of that previously reported with PI3K inhibitors, and objective responses were obtained in women with PIK3CA-mutated and -mutation-not-detected tumors. On this basis, taselisib plus fulvestrant is being evaluated in a phase III study.Plasma cell-free DNA (cfDNA) analysis has emerged as a powerful noninvasive tool for cancer genotyping and detection. Hu and colleagues report on a surprising source of tumor-plasma discordance and false-positive plasma genotyping – mutant DNA derived from peripheral blood cells (PBC), known as clonal hematopoiesis (CH). Through paired tumor, cfDNA, and PBC analysis the investigators identify that most JAK2 mutations, some TP53 mutations, and rare KRAS mutations in cfDNA can be traced to CH. Thus, mutations detected in cfDNA may not always reflect tumor genotype, impacting how cfDNA genomics evolves further as a tool for cancer genotyping and detection.Machine learning based on the radiomics of multimodal magnetic resonance images (MRI) provides an alternative for noninvasive assessment of glioma subtypes in line with 2016 WHO classification. A three-level machine-learning model was proposed to stratify molecular subtypes of gliomas. The accuracies of classifications for the IDH and 1p/19q status of gliomas were between 87.7% and 96.1%. The complete classification of five molecular subtypes solely based on the MRI radiomics achieved an 81.8% accuracy, and a higher accuracy of 89.2% could be achieved if the histology diagnosis is available. The proposed approach can add value in the molecular diagnosis of gliomas by clinical MRI.

Prognostic Implications of Multiplex Detection of KRAS Mutations in Cell-Free DNA from Patients with Pancreatic Ductal Adenocarcinoma.

Cell-free DNA (cfDNA) is known to provide potential biomarkers for predicting clinical outcome, but its value in pancreatic ductal adenocarcinoma (PDAC) has not been fully evaluated. The aim of this study was to evaluate the clinical applicability of quantitative analysis of multiplex KRAS mutations in cell-free DNA from patients with PDAC. A total of 106 patients with PDAC were enrolled in this prospective study. The concentration and fraction of KRAS mutations were determined through multiplex detection of KRAS mutations in plasma samples by use of a droplet digital PCR kit (Bio-Rad). KRAS mutations were detected in 96.1% of tissue samples. Eighty patients (80.5%) harbored KRAS mutations in cfDNA, with a median KRAS mutation concentration of 0.165 copies/μL and a median fractional abundance of 0.415%. Multivariable analyses demonstrated that the KRAS mutation concentration [hazard ratio (HR), 2.08; 95% CI, 1.20-3.63] and KRAS fraction (HR, 1.73; 95% CI, 1.02-2.95) were significant factors for progression-free survival. KRAS mutation concentration (HR, 1.97; 95% CI, 1.05-3.67) also had prognostic implications for overall survival. Subgroup analyses showed that KRAS mutation concentration and fractional abundance significantly affected progression-free survival in resectable PDAC (P = 0.016). Moreover, when combined with the cancer biomarker CA19-9, the KRAS mutation concentration in cfDNA showed additive benefits for the prediction of overall survival. This study demonstrates that multiplex detection of KRAS mutations in plasma cfDNA is clinically relevant, providing a potential candidate biomarker for prognosis of PDAC.

KRAS mutations in cell-free DNA from preoperative and postoperative sera as a pancreatic cancer marker: a retrospective study

Background:Pancreatic ductal adenocarcinoma (PDAC) has very poor prognosis despite existing multimodal therapies. This study aimed to investigate whether KRAS mutations at codons 12/13 in cell-free DNA (cfDNA) from preoperative and postoperative sera from patients with PDAC can serve as a predictive biomarker for treatment response and outcomes after surgery.Methods:Preoperative and postoperative serum samples obtained from 45 patients with PDAC whom underwent curative pancreatectomy at our institution between January 2013 and July 2016 were retrospectively analysed. Peptide nucleic acid-directed PCR clamping was used to identify KRAS mutations in cfDNA.Results:Among the 45 patients enrolled, 11 (24.4%) and 20 (44.4%) had KRAS mutations in cfDNA from preoperative and postoperative sera, respectively. Multivariate analysis revealed that KRAS mutations in postoperative serum (hazard ratio (HR)=2.919; 95% confidence interval (CI)=1.109–5.621; P=0.027) are an independent prognostic factor for disease-free survival. Furthermore, the shift from wild-type KRAS in preoperative to mutant KRAS in postoperative cfDNA (HR=9.419; 95% Cl=2.015–44.036; P=0.004) was an independent prognostic factor for overall survival.Conclusions:Changes in KRAS mutation status between preoperative and postoperative cfDNA may be a useful predictive biomarker for survival and treatment response.

The prognostic value of KRAS mutation by cell-free DNA in cancer patients: A systematic review and meta-analysis.

KRAS mutation has been found in various types of cancer. However, the prognostic value of KRAS mutation in cell-free DNA (cfDNA) in cancer patients was conflicting. In the present study, a meta-analysis was conducted to clarify its prognostic significance. Literature searches of Cochrane Library, EMBASE, PubMed and Web of Science were performed to identify studies related to KRAS mutation detected by cfDNA and survival in cancer patients. Two evaluators reviewed and extracted the information independently. Review Manager 5.3 software was used to perform the statistical analysis. Thirty studies were included in the present meta-analysis. Our analysis showed that KRAS mutation in cfDNA was associated with a poorer survival in cancer patients for overall survival (OS, HR 2.02, 95% CI 1.63–2.51, P<0.01) and progression-free survival (PFS, HR 1.64, 95% CI 1.27–2.13, P<0.01). In subgroup analyses, KRAS mutation in pancreatic cancer, colorectal cancer, non-small cell lung cancer and ovarian epithelial cancer had HRs of 2.81 (95% CI 1.83–4.30, P<0.01), 1.67 (95% CI 1.25–2.42, P<0.01), 1.64 (95% CI 1.13–2.39, P = 0.01) and 2.17 (95% 1.12–4.21, p = 0.02) for OS, respectively. In addition, the ethnicity didn’t influence the prognostic value of KRAS mutation in cfDNA in cancer patients (p = 0.39). Prognostic value of KRAS mutation was slightly higher in plasma than in serum (HR 2.13 vs 1.65), but no difference was observed (p = 0.37). Briefly, KRAS mutation in cfDNA was a survival prognostic biomarker in cancer patients. Its prognostic value was different in various types of cancer.

Abstract 5688: Routine testing for KRAS mutations in cfDNA from blood of advanced cancer patients

Abstract Background: Mutations in the KRAS proto-oncogene, GTPase (KRAS) are driver alterations in several tumors, such as non-small-cell lung (NSCLC) and colorectal cancer (CRC). However, their role as a prognostic marker in liquid biopsies is unclear. We studied the status of KRAS mutations in the peripheral blood of advanced NSCLC and colorectal cancer patients visited in our hospital and evaluated its potential value as a monitoring marker in the clinical practice. Methods: We developed a sensitive TaqMan assay, in the presence of a PNA clamp, for the determination of KRAS mutations (codons 12, 13 and 61) in circulating-free DNA (cfDNA). The assay detected 2.5 pg mutated DNA/µL and a ratio of KRAS mutated versus wild type allele of 1:20000 and was validated in 80 cancer patients previously genotyped in tumor tissue showing a clinical sensitivity of 72.5% and specificity of 100%. cfDNA was isolated from serum and plasma specimens, using an automatic extractor and mutational analyses were performed in quadruplicates samples. Serum and plasma samples were drawn at diagnosis, during follow-up and progression. Results: 239 NSCLC and 11 colorectal cancer patients were screened for KRAS mutations in cfDNA at presentation in the period of 2013 to 2016. In addition, 160 cfDNA samples collected during disease monitoring of 61 patients were analyzed. Paired biopsies were available from 110/250 p at diagnosis (60 positive for KRAS in FFPE and 50 WT). The KRAS mutation was detected in the cfDNA of 76.6% (46/60) p positive in tumor tissue vs. only in 1/50 WT patients where a G12C was detected in cfDNA in a consistent manner, probably associated with a heterogeneity of the tumor. In patients with no biopsy available, we detected KRAS mutations in cfDNA in 14.3% (20/140) cases at diagnosis. The most prevalent mutations observed in cfDNA were G12C (44.7 %), G12V (22.4%) and G12D (10.4%) for NSCLC patients and G13D (5.9%) for colorectal patients. The Q61H mutation was detected in the cfDNA of one NSCLC and one CRC p. Of the 67 patient’s positive in cfDNA at presentation, KRAS mutations were detected in serum and plasma in 38 patients, only in plasma in 24 and only in serum in 5. Regarding the 61 patients with serial blood samples, we observed a correlation between the KRAS mutation load in cfDNA and the course of the disease, with a decrease in patients responding to chemotherapy and an increase during disease progression. Conclusions: Our results demonstrate the feasibility of KRAS mutation analysis in the cfDNA of advanced NSCLC and colorectal patients. Analysis of KRAS mutations in the blood of mutated patients can have a value in patients with no biopsy available and to monitor the course of the disease. Citation Format: Mónica Garzón Ibañez, Clara Mayo de las casas, Nùria Jordana Ariza, Ariadna Balada Bel, Beatriz Garcia, Sergio Villatoro, Jordi Bertrán-Alamillo, Alejandro Martinez-Bueno, Santiago Viteri Ramirez, Ana Pérez Rosado, Daniela Morales Espinosa, Maria José Catalán, Niki Karachaliou, Miguel Ángel Molina-Vila, Rafael Rosell. Routine testing for KRAS mutations in cfDNA from blood of advanced cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5688. doi:10.1158/1538-7445.AM2017-5688

Abstract 5680: Clinical significance of low frequency EGFR and KRAS mutations of cell free DNA using Ion AmpliSeq Cancer Hotspot Panel in lung cancer patients

Abstract Cell free DNA (cfDNA) present in the blood stream shows great potential as a useful cancer marker for molecular diagnosis and cancer progression monitoring. Especially, analyzing the cfDNA with Next Generation Sequencing (NGS) technology allows high through put examination of various genes concurrently at a low cost. However, there are still debates regarding clinically meaningful variant frequency to identify mutations in cfDNA, especially with ultra-deep sequencing. In this study, we examined the clinical utility of Ion AmpliSeq Cancer Hotspot Panel v2 (ICP; Ion Torrent) with Proton platforms. ICP, covering 2800 COSMIC mutations from 50 cancer genes was used to analyze cfDNA of 125 serum samples from lung cancer patients. The percentage of on target was 92% with mean depth of 22,868x. We identified aberrations of TP53 (72%), EGFR (43%), PTEN (26%), PIK3CA (26%), BRAF (16%), KRAS (14%), KIT (10%) and RET (10%) with the cut-off criteria of variant frequency &amp;gt;0.1% and p&amp;lt;0.01. To validate the results, we analyzed EGFR gene status by direct sequencing in available 100 FFPE tumor tissues (tDNA). Out of 17 patients with EGFR mutations in tDNA, 9 patients showed very low frequency (&amp;lt;0.05%) of same EGFR mutation in cfDNA. To validate the results of ICP, droplet digital PCR (ddPCR) was carried out with same cfDNA. From those 9 patients, EGFR mutations in cfDNA were detected in five patients (minimum frequency 0.01%) by ddPCR. From the patients with wild type EGFR in tDNA, EGFR exon 19 deletion or exon 21 point mutation were detected by ICP in 19 patients using cfDNA. Again, ddPCR was carried out with same cfDNA to confirm the result. EGFR mutations were confirmed in nine patients (47.4%) by cfDNA ddPCR and among the 6 patients treated with EGFR TKI, 4 patients showed response or stabilization of disease. Also, we identified 18 patients with KRAS mutations in ICP results of 125 cfDNA. The result of ddPCR was matched in 80% of patients. Interestingly, 2 patients had multiple KRAS mutations in cfDNA with ICP as well as ddPCR. In our study, we demonstrated that ICP with Proton system is a useful assay to identify somatic mutations using cfDNA in lung cancer patients. Also, we suggest that even EGFR mutation of very low frequency (&amp;lt;0.05%) might have clinical significance in NGS analysis using cfDNA. Serial blood sample obtained during treatment in these patients will be analyzed by ICP and ddPCR. [This research was supported by the Korea Health Technology R&amp;D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health &amp; Welfare, Republic of Korea (HI14C0066)] Citation Format: Jae Sook Sung, Jong Won Lee, Boyeon Kim, Saet Byeol Lee, Chang Won Park, Hae Mi Kim, Nak-Jung Kwon, Won Jin Jang, Yoon Ji Choi, Jung Yoon Choi, Eun Joo Kang, Kyung Hwa Park, Sung Yong Lee, Yeul Hong Kim. Clinical significance of low frequency EGFR and KRAS mutations of cell free DNA using Ion AmpliSeq Cancer Hotspot Panel in lung cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5680. doi:10.1158/1538-7445.AM2017-5680

Monitoring KRAS mutations in circulating DNA and tumor cells using digital droplet PCR during treatment of KRAS-mutated lung adenocarcinoma

Liquid biopsies are a new non-invasive strategy to detect and monitor the biology of non-small-cell lung cancer (NSCLC) in the era of personalized medicine. KRAS is an oncogenic driver that is mutated in 30% of NSCLCs and is associated with a poor prognosis. 62 samples from 32 patients, treated for metastatic KRAS-mutated lung adenocarcinoma, had DNA extracted from plasma and circulating tumor cells (CTCs) prospectively tested for the presence of KRAS mutations using droplet digital PCR. A KRAS mutation was detected in 82% of patients. Sensitivity was 78% for circulating free DNA (cfDNA) and 34% for CTCs. The presence of a KRAS mutation in cfDNA was correlated with a poor response to chemotherapy or targeted therapy. When a KRAS-mutated-DNA was detected and then monitored in cfDNA, its variation during targeted or conventional therapy was correlated with response, according to RECIST criteria, in 87.5% of cases (n=14/16), whereas this correlation was observed in 37.5% of cases for CTCs (n=3/8). We report the usefulness of using digital droplet PCR on liquid biopsies to predict and monitor responses to treatment of KRAS-mutated lung adenocarcinoma. ctDNA was much more sensitive than CTCs in this context.

Abstract 493: Quantity of KRAS mutations in cell-free DNA is associated with survival of patients with advanced cancers

Abstract Background: Cell-free (cf) DNA from plasma offers an easily obtainable material for KRAS mutation analysis for diagnostics and monitoring. There is emerging evidence that the percentage of mutant cfDNA in the wild-type background (mutant allele fraction, MAF) and/or absolute quantity of mutant cfDNA can be associated with survival of patients with advanced cancers. Methods: Plasma-derived cfDNA from patients with progressing advanced cancers was purified and 16 ng of DNA was tested with a KRAS multiplex assay to distinguish the wild-type allele from 7 of the most common mutations in the G12 and G13 hotspot of exon 2 using the QX200 Droplet Digital PCR™ platform (Bio-Rad). Results were compared to mutation analysis of archival primary or metastatic tumor tissue obtained at different points of clinical care from a CLIA-certified laboratory and clinical outcomes including survival. Results: Of the 117 patients (colorectal cancer, 71; non-small cell lung cancer, 12; melanoma, 10; pancreatic cancer, 5; ovarian cancer, 5; appendiceal cancer, 5; other cancers, 9), KRAS mutations were detected in 85 (73%) archival FFPE tumor samples and 85 (73%) plasma cfDNA samples. The two methods had overall agreement in 109 patients (93%; kappa, 0.83, standard error, 0.06; 95% confidence interval [CI], 0.71-0.94), sensitivity of 95% (95% CI, 0.88-0.99), specificity of 88% (95% CI, 0.71-0.96), even though median time from tissue to blood sampling was 18.5 months (1.1-134.4 months). A higher MAF (&amp;gt;7%) of KRAS in cfDNA as determined by 5% trimmed mean value was associated with shorter survival compared to lower (&amp;lt;7%) MAF (5.4 vs. 7.6 months; P = 0.001), which was confirmed on multivariate analysis. A total of 20 patients with KRAS mutations in cfDNA had longitudinal testing of cfDNA from at least two time points obtained before and on experimental therapy. In these patients, changes in MAF demonstrated a trend towards positive correlation with changes in measurement of target tumor lesions on imaging per RECIST (r = 0.42, P = 0.07). Conclusions: A higher percentage of KRAS mutation in plasma cfDNA is an independent predictive factor for shorter survival in patients with advanced cancers. Citation Format: Kiran Madwani, Helen J. Huang, Dawne N. Shelton, Siqing Fu, Apostolia M. Tsimberidou, Sarina A. Piha-Paul, Aung Naing, David S. Hong, Daniel D. Karp, Debra L. Andrews, Goran Cabrilo, E. Scott Kopetz, Rajyalakshmi Luthra, Bryan K. Kee, Cathy Eng, Van K. Morris, George A. Karlin-Neumann, Funda Meric-Bernstam, Filip Janku. Quantity of KRAS mutations in cell-free DNA is associated with survival of patients with advanced cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 493.

Abstract 3137: NGS-based detection of KRAS hotspot mutations in plasma cell-free DNA of pancreatic cancer cases

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is characterized by hotspot mutations in the KRAS gene (codons 12, 13 or 61) in 85-90% of cases. Codon 12 KRAS mutations have been detected in pancreatic juice, blood and stool samples from pancreatic cancer cases and represent promising biomarkers for early detection. However, the proportion of tumor-derived KRAS mutations in cell-free DNA fragments (cfDNA) has shown large variations, probably because of the heterogeneity in biosamples and assays tested. Deep sequencing technologies (NGS) allow the identification of low-abundance somatic variants, but have not previously been applied to the detection of KRAS hotspot mutations in cfDNA of PDAC cases. Moreover, variant calling methods have rarely been tested against cancer-free individuals so the proportion of false positives is unknown. We investigated whether deep sequencing of KRAS mutations at codons 12, 13 and 61 in plasma samples could represent a robust assay to distinguish pancreatic cancer from chronic pancreatitis and healthy controls. Methods: We developed an Ion Torrent-based NGS KRAS assay (partial exons 2 and 3, totalling 208bp) to screen cfDNA from plasma samples of 461 PDAC cases, 154 individuals with chronic pancreatitis and 421 healthy controls. cfDNA extraction (&amp;gt;4ng) and sequencing (&amp;gt;1000x coverage on average, and absence of systematic high sequencing error rates on the 208bp) performed well on 431 (93%) PDAC cases, 138 (90%) chronic pancreatitis, and 388 (95%) controls. We fit a robust negative-binomial regression to estimate the distribution of the sequencing errors at each DNA bp position and identified outlying samples, which were considered as KRAS positive when q-value&amp;lt;10-3. We also estimated the detection threshold of our assay using serial dilutions of DNA from SW480 KRAS mutated cell-line (p.G12V) in wild-type DNA. Results: Sequencing of the serial dilutions of KRAS p.G12V mutated DNA indicated a detection threshold at a minor allele frequency of 0.2%. KRAS mutations in cfDNA were detected in 83 (19.3%) PDAC cases (73 on codon 12; 8 on codon 61; 1 on codon 13; and 1 multiple codons, i.e., similar in proportions as reported in tumor tissue from the International Cancer Genomic Consortium); 3 (2.2%) chronic pancreatitis (all on codon 12); and 8 (2.1%) healthy controls (4 on codon 12 and 4 on codon 61). Stage was significantly associated with the proportion of detected mutations in cancer cases (chi-squared p = 0.0005): the proportions of cases with detectable KRAS mutations in plasma were 7.9%, 14.9%, and 31.1% for local, regional, and advanced stages, respectively. Conclusions: The NGS-based KRAS mutation screening is a sensitive approach to detect low allelic fraction in plasma cfDNA, although its utility for early detection is still limited. However, it has the capacity to identify specific KRAS mutations, which could be useful in a panel of other non-invasive biomarkers. Citation Format: Florence Le Calvez-Kelm, Matthieu Foll, Magdalena B. Wozniak, Geoffroy Durand, Priscilia Chopard, Maroulio Pertesi, Tiffany Delhomme, Ivana Holcatova, Lenka Foretova, Vladimir Janout, Eleonora Fabianova, Maxime P. Vallée, Paul Brennan, James D. McKay, Graham Byrnes, Ghislaine Scélo. NGS-based detection of KRAS hotspot mutations in plasma cell-free DNA of pancreatic cancer cases. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3137.

Abstract 3157: Serial droplet digital PCR (ddPCR) of plasma cell-free DNA (cfDNA) as pharmacodynamic (PD) biomarker in Phase 1 clinical trials for patients (pts) with KRAS mutant non-small cell lung cancer (NSCLC)

Abstract Introduction: Phase 1 clinical trials of novel therapeutics have historically focused on toxicity, but increasingly are doubling as efficacy studies in biomarker-enriched populations. Given the small sample sizes (∼3-6 patients per dose), response on imaging may be a coarse marker of therapeutic effect. Here we piloted serial ddPCR of plasma cfDNA as a PD marker in a phase I combination study of a MEK inhibitor and a CDK 4/6 inhibitor in patients with RAS mutated cancers. Methods / Results: Twenty-five pts with RAS-mutated cancer (incl. 17 patients with KRAS-mutant NSCLC) have been enrolled to date in a phase I dose escalation trial of the MEK inhibitor PD-0325901 with the CDK4/6 inhibitor palbociclib (NCT02022982). Plasma for cfDNA genotyping was collected at baseline prior to therapy and at the beginning of cycle 2. Plasma genotyping for KRAS G12X mutations was performed using a validated and highly quantitative droplet digital PCR assay. Pts were enrolled in 5 dose level cohorts ranging from 75 mg palbociclib daily (3 weeks on, 1 week off) with 2 mg PD-0325901 BID (3 weeks on 1week off) to 125 mg palbociclib daily with 8 mg PD-0325901 BID (Table). KRAS mutations were detected in 14/24 pts at baseline (59%, median 1402 copies/mL plasma, range: 11-93000), consistent with the previously reported sensitivity of 64%. A second blood draw at cycle 2 was obtained for all 14 pts. A positive plasma response, defined as decrease of KRAS G12X mutants from first to second dose, was observed in 6 pts (range -6% - -100%) with the most plasma responders (n = 4 pts) at the maximum administered dose. At lower administered doses, there was a median increase in plasma KRAS mutant levels. Conclusions: Increasing dose levels resulted in more consistent decreases in KRAS mutation in cfDNA, consistent with a dose-dependent pharmacodynamic effect.These results highlight the potential value of serial plasma ddPCR as a PD marker in early phase clinical trials. Dose LevelPalbociclib (QD, 3 wks on 1 wk off) mgPD-0325901 (BID, 3 wks on 1 wk off) mgN Enrolled (N analyzed)Median Plasma change KRAS mut(%)17523 (1)+2427543 (3)+60 (range +31 - +150)310048 (4)+150 (range -6 - +341)412544 (2)+9 (range -45 - +61)512587 (4)-27 (range -7 - -43) Citation Format: Cloud P. Paweletz, Geoffrey R. Oxnard, Nora Feeney, John F. Hilton, Leena Gandhi, Khanh T. Do, Adrienne Anderson, Andrew Wolanski, Alexander Tejeda, Jessie M. English, Paul T. Kirschmeier, Pasi A. Jänne, Geoffrey I. Shapiro. Serial droplet digital PCR (ddPCR) of plasma cell-free DNA (cfDNA) as pharmacodynamic (PD) biomarker in Phase 1 clinical trials for patients (pts) with KRAS mutant non-small cell lung cancer (NSCLC). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3157.

Abstract 5607: BRAF and KRAS mutation testing in plasma cell-free DNA with ICE COLD-PCR in patients with advanced cancers

Abstract Background: Cell-free (cf) DNA in the plasma of cancer patients offers an easily obtainable, low-risk, inexpensive, and repeatedly available source of biologic material for mutation analysis and monitoring of molecular changes throughout cancer therapy. Methods: DNA in plasma from patients with advanced cancers who progressed on systemic therapy was tested for BRAF V600 and KRAS G12 and G13 mutations using the ICE COLD-PCR platform. ICE COLD-PCR, “Improved and Complete Enrichment COamplification at Lower Denaturation,” selectively amplifies mutant DNA by exploiting differences in denaturation temperatures between mutant DNA duplexes and normal “wild-type” DNA duplexes. KRAS Exon 2 and BRAF Exon 15 ICE COLD-PCR was performed on plasma samples. Amplicons were analyzed using Sanger sequencing and results were compared to the mutation status of archival primary or metastatic tumor tissue as determined in a CLIA-certified laboratory during routine clinical care. Results: Plasma samples from 77 patients with advanced cancers and known tumor tissue BRAF and/or KRAS mutation status (colorectal cancer, n=38; melanoma, n=17; non-small cell lung cancer, n=7; other cancers, n=15) were obtained before treatment and, if possible, sequentially during therapy and tested for BRAF (42), KRAS (34) or BRAF and KRAS (1) mutations in cfDNA. BRAF mutations were detected in 93% (40/43) of archival tumor samples compared to 70% (30/43) of plasma cfDNA samples (agreement 77%). In addition, 20 patients treated with systemic therapy had serial plasma samples collected and the change in relative abundance of BRAF-mutant compared to wild-type cfDNA corresponded with the clinical course of 15 patients and was discrepant for 1 patient; in 5 patients no BRAF mutated cfDNA was detected at any time point. KRAS mutations were detected in 83% (29/35) of archival tumor samples compared to 74% (26/35) of plasma cfDNA samples (agreement 80%). In addition, 12 patients treated with systemic therapy had serial plasma collected and the change in relative abundance of KRAS-mutant compared to wild-type cfDNA corresponded with clinical course in 10 patients; in 2 patients no KRAS mutated cfDNA was detected at any time point. Conclusions: Detection of BRAF and KRAS mutations in cfDNA can provide a fast and noninvasive alternative to mutation testing in tumor tissue with a potential to be used for monitoring response to cancer therapy. Citation Format: Filip Janku, Ben Legendre, Katherine Richardson, Gerald S. Falchook, Aung Naing, Veronica R. Holley, Siqing Fu, David S. Hong, Sarina A. Piha-Paul, Jennifer J. Wheler, Ralph G. Zinner, Vivek Subbiah, Apostolia M. Tsimberidou, Daniel D. Karp, Vanda M. Stepanek, Goran Cabrilo, Rajyalakshmi Luthra, Funda Meric-Bernstam, Agop Y. Bedikian, Bryan K. Kee, Cathy Eng, Michael J. Overman, Kevin B. Kim, Amy Kruempel, Jaclyn Pope, Courtney Cubrich, Grant Wu, Marcia Lewis, Razelle Kurzrock. BRAF and KRAS mutation testing in plasma cell-free DNA with ICE COLD-PCR in patients with advanced cancers. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5607. doi:10.1158/1538-7445.AM2014-5607

Abstract B26: Actionable mutations in cell-free DNA in plasma of patients with advanced cancers referred for experimental targeted therapies.

Abstract Background: Actionable mutations confer a survival advantage to cancer cells and can provide therapeutic targets. Cell-free (cf) DNA in the plasma of cancer patients offers an easily obtainable, low-risk, and inexpensive source of biologic material for mutation analysis. Methods: cfDNA in plasma samples from patients with advanced cancers who progressed on systemic therapy was tested for 21 mutations in BRAF (codon 600), EGFR (exons 19-21), KRAS (codons 12, 13), and PIK3CA (exons 9, 20) using the BEAMing method. Results were compared to mutation analysis results from archival primary or metastatic tumor tissue from a CLIA-certified laboratory. Results: cfDNA was extracted from 155 patients with advanced cancers. BRAF mutations were detected in 27% (33/122) plasma samples and in 30% (37/122) of archival tumor samples resulting in agreement in 88.5% cases (kappa=0.72, 95% confidence interval [CI] 0.58- 0.86). EGFR mutations were detected in 8% (6/77) plasma samples and in 6% (5/77) tumor samples resulting in agreement in 98.7% cases (kappa=0.90, 95% CI 0.71- 1.09). KRAS mutations were detected in 50% (55/110) of plasma samples and in 53% (58/110) of tumor samples, resulting in agreement in 82.7% cases (kappa=0.66, 95% CI 0.51- 0.80). PIK3CA mutations were detected in 20% (19/94) of plasma samples and in 14% (13/94) of tumor samples, resulting in concordance in 91.5% cases (kappa=0.70, 95% CI 0.51- 0.89). Of interest, 2 of 9 patients with BRAF mutations (both melanoma) in the tumor, but not in cfDNA had plasma collection at the time of progression on prior BRAF targeting therapy. Also, a patient with V600E BRAF-mutated melanoma, who previously progressed on a MEK inhibitor, displayed a G12R KRAS mutation in cfDNA and a patient with V600K BRAF-mutated melanoma with additional E542K and H1047R PIK3CA mutations in cfDNA was ultimately refractory to BRAF inhibitor treatment. Also, a V600K BRAF mutation was found in the cfDNA of a patient with colorectal cancer and a G12V KRAS mutation. In addition, 2 patients with EGFR-mutated lung adenocarcinoma (exon 19 and L858R), who progressed on erlotinib, had T790M EGFR (n=2) and E545K PIK3CA (n=1) mutations in cfDNA, plausibly explaining secondary resistance to erlotinib. A patient with Erdheim-Chester disease and a V600E BRAF mutation also had a T790M EGFR mutation in cfDNA. Finally, a patient with H1047R PIK3CA mutant ovarian cancer showed an additional G12C KRAS mutation in cfDNA and experienced a partial response followed by early progression on a PI3K inhibitor. Patient characteristics, mutation types and detailed discrepancy analysis will be presented. Conclusions: Detecting actionable mutations in cfDNA is a noninvasive alternative to mutation testing in tumor tissue with an acceptable level of concordance, and should be investigated further for selecting appropriate targeted therapies and monitoring mutation profiles. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B26. Citation Format: Filip Janku, Philipp Angenendt, Aung Naing, Gerald S. Falchook, Apostolia M. Tsimberidou, Veronica R. Holley, Siqing Fu, David S. Hong, Jennifer J. Wheler, Sarina A. Piha-Paul, Ralph G. Zinner, Daniel D. Karp, Vivek Subbiah, Kevin B. Kim, Funda Meric-Bernstam, Frank Diehl, Razelle Kurzrock. Actionable mutations in cell-free DNA in plasma of patients with advanced cancers referred for experimental targeted therapies. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B26.

Abstract C203: BRAF and KRAS mutation testing in cell-free DNA and circulating tumor cells from blood of patients with metastatic cancers.

Abstract Background: Cell-free (cf) DNA and circulating tumor cells (CTC) in the blood of cancer patients offer an easily obtainable, low-risk, inexpensive, and repeatedly available source of biologic material for mutation analysis and monitoring of molecular changes throughout cancer therapy. Methods: DNAs from plasma and CTC from patients with advanced cancers who progressed on systemic therapy were tested for BRAF V600 and KRAS G12/G13 mutations using the ICE-COLD-PCR platform. ICE COLD-PCR, "Improved and Complete Enrichment COamplification at Lower Denaturation” selectively amplifies mutant DNA by exploiting differences in denaturation temperatures between mutant DNA duplexes and normal “wild-type” DNA duplexes. KRAS Exon 2 and BRAF Exon 15 ICE COLD-PCR was performed on plasma samples, and from matched CTCs collected using ScreenCell® MB kits (ScreenCell, Sarcelles, France). Amplicons were analyzed by Sanger sequencing methods and results were compared to the mutation status of the archival primary or metastatic tumor tissue as determined in a CLIA-certified lab. Results: Blood samples from 59 patients with advanced cancers (colorectal cancer, n=32; melanoma, n=12; non-small cell lung cancer, n=7; other cancers, n=8), were obtained before treatment and, if possible, sequentially during therapy and tested for BRAF (30), KRAS (29) or BRAF and KRAS (1) mutations. BRAF mutations were detected in 97% (30/31) of archival tumor samples compared to 65% (20/31) of cfDNA samples (agreement 68%) and to 3% (1/31) of CTC samples (agreement 6%). KRAS mutations were detected in 90% (26/29) of archival tumor samples compared to 86% (25/29) of cfDNA samples (agreement 83%) and to 10% (3/29) of CTC samples (agreement 21%); however, CTCs had different KRAS mutation subtypes than those in tumor tissue. Of interest, in 3 patients with serial blood collection for cfDNA BRAF mutations, 2 (melanoma, Erdheim-Chester disease) had BRAF V600E cfDNA mutations at baseline, which disappeared during the response to subsequent therapy. Another patient (melanoma) did not have a BRAF V600E cfDNA mutation immediately after being taken off BRAF inhibitor therapy due to intolerance, but a BRAF V600E cfDNA mutation emerged when the patient was treated with non-BRAF targeting therapy. In 2 patients with serial blood collections for cfDNA KRAS mutations, 2 (colorectal cancer) did not have KRAS cfDNA mutations at baseline, but KRAS cfDNA mutations (G13D, G12D, respectively) emerged following disease progression and subsequent therapy. Conclusions: Detection of BRAF and KRAS mutations in cfDNA can provide a fast and noninvasive alternative to mutation testing in tumor tissue. Although these mutations can be also detected in CTC, the level of concordance with tumor tissue results is low. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C203. Citation Format: Filip Janku, Ben Legendre, Katherine Richardson, Gerald S. Falchook, Aung Naing, Veronica R. Holley, David S. Hong, Ralph G. Zinner, Siqing Fu, Apostolia M. Tsimberidou, Vivek Subbiah, Daniel D. Karp, Sarina A. Piha-Paul, Jennifer J. Wheler, Vanda M. Stepanek, Goran Cabrilo, Rajyalakshmi Luthra, Funda Meric-Bernstam, Amy Kruempel, Jaclyn Pope, Courtney Cubrich, Grant Wu, Yanggu Shi, Marcia Lewis, Razelle Kurzrock. BRAF and KRAS mutation testing in cell-free DNA and circulating tumor cells from blood of patients with metastatic cancers. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C203.

Genetic and molecular biomarker characterization of KRAS mutant non-small cell lung carcinoma (NSCLC) tumors.

11026 Background: Preclinical studies demonstrated Brahma related gene 1 (BRG1) mutations or loss of expression, and mutations of LKB1 may be associated with lack of sensitivity for MEK inhibitor trametinib in a subset of KRAS mutant NSCLC lines. This study aimed to evaluate the frequency of KRAS, LKB1 and BRG1 mutations in NSCLC tumors; and determine whether KRAS mutations in corresponding plasma samples could be detected by evaluating circulating cell-free DNA (cfDNA). Methods: Human NSCLC FFPE tumor tissue and matched plasma samples were procured from Indivumed GmbH. KRAS mutation status of 101 NSCLC tumors and matched plasma were determined by direct sequencing of genomic DNA (gDNA) from tissue and/or BEAMing on tissue gDNA or plasma cfDNA. Genetic mutations of LKB1 and BRG1 were determined by direct sequencing. Additional mutations were determined using the Ion Torrent AmpliSeq Cancer Panel. BRG1 protein expression was evaluated by IHC. Results: By direct sequencing and BEAMing we found 27/101 (28.4%) NSCLC tissue and/or plasma samples harbored KRAS mutations: G12V (37.0%), G12C (29.6%), G12D (18.5%), G12S, G13C, G13D and Q61H (3.7% each). The KRAS mutation status concordance (mutant or wild-type) between tumor gDNA and plasma cfDNA was 79-81%. Among the KRAS mutant tumors, LKB1 and BRG1 mutations were detected in 10/26 (38%) and 1/26 (3.8%) tumors respectively by direct sequencing. By IHC, loss of BRG1 expression was detected in 1/21 KRAS mutant tumors. The mutation frequency and variants for KRAS and LKB1 in patient samples were comparable with KRAS mutant NSCLC cell lines and COSMIC database. However the frequency of BRG1 mutation and protein loss were much lower in patient tumors. In a subset of 15 KRAS mutant tumors, Ion Torrent confirmed KRAS and LKB1 mutations and provided additional mutations found in TP53, FGFR2, FGFR3, GNAS, KDR, KIT and MET. Conclusions: This study demonstrates that KRAS mutant NSCLC tissues have high frequency of LKB1 mutations along with other mutations. It also supports the feasibility of detection of KRAS mutations in cfDNA from blood of NSCLC patients using BEAMing technology, providing an alternative to invasive biopsy.