Efficacy Of anti-EGFR Therapy Research Articles

Novel Insights of Anti-EGFR Therapy in HNSCC: Combined with Immunotherapy or Not?

The efficacy of anti-EGFR therapy is still unfavorable in recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) patients. Disorder of antitumor immunity and aberrantly expressed checkpoint biomarkers had been validated to involve anti-EGFR therapy tolerance and efficacy. Here we review the immunomodulation of anti-EGFR therapy in the tumor immune microenvironment (TIME) of HNSCC and assist clinicians in finding the potential strategies to rescue anti-EGFR tolerance therapy in the era of immunotherapy for HNSCC. Anti-EGFR therapy, especially cetuximab, was validated to induce the innate and adaptive immune responses of HNSCC patients. It is mainly through inducing natural killer (NK) cells mediating antibody-dependent cell-mediated cytotoxicity (ADCC), recruiting multiple tumor-infiltrating immune cells, and finally remodeling the TIME. Moreover, mountains of preclinical models and clinical trials revealed that combining anti-EGFR agents with immunotherapy could enhance the antitumor effectiveness in HNSCC. Anti-EGFR therapy may usher in another dawn in the treatment of patients with HNSCC through combination with immunotherapy. We offer an overview of the ongoing efforts to make out the immunomodulation of the EGFR pathway in both innate and adaptive immune responses; update the constant preclinical models and clinical trials for the combination of anti-EGFR and immunotherapy in HNSCC; and finally evaluate the efficacy and advantages of the combination therapeutic strategies in clinical use.

Molecular subtype-specific efficacy of anti-EGFR therapy in colorectal cancer is dependent on the chemotherapy backbone

BackgroundPatient selection for addition of anti-EGFR therapy to chemotherapy for patients with RAS and BRAF wildtype metastatic colorectal cancer can still be optimised. Here we investigate the effect of anti-EGFR therapy on survival in different consensus molecular subtypes (CMSs) and stratified by primary tumour location.MethodsRetrospective analyses, using the immunohistochemistry-based CMS classifier, were performed in the COIN (first-line oxaliplatin backbone with or without cetuximab) and PICCOLO trial (second-line irinotecan with or without panitumumab). Tumour tissue was available for 323 patients (20%) and 349 (41%), respectively.ResultsWhen using an irinotecan backbone, anti-EGFR therapy is effective in both CMS2/3 and CMS4 in left-sided primary tumours (progression-free survival (PFS): HR 0.44, 95% CI 0.26–0.75, P = 0.003 and HR 0.12, 95% CI 0.04–0.36, P < 0.001, respectively) and in CMS4 right-sided tumours (PFS HR 0.17, 95% CI 0.04–0.71, P = 0.02). Efficacy using an oxaliplatin backbone was restricted to left-sided CMS2/3 tumours (HR 0.57, 95% CI 0.36–0.96, P = 0.034).ConclusionsThe subtype-specific efficacy of anti-EGFR therapy is dependent on the chemotherapy backbone. This may provide the possibility of subtype-specific treatment strategies for a more optimal use of anti-EGFR therapy.

The efficacy of anti-EGFR therapy in treating metastatic colorectal cancer differs between the middle/low rectum and the left-sided colon

BackgroundClinically, metastatic rectal cancer has been considered a subset of left-sided colon cancer. However, heterogeneity has been proposed to exist between high and middle/low rectal cancers. We aimed to examine the efficacy of anti-epidermal growth factor receptor (EGFR) treatment for middle/low rectal and left-sided colon cancers.MethodsThis study enrolled 609 patients with metastatic colorectal cancer who were treated with anti-EGFR therapy. They were divided into groups based on primary tumour locations: the right-sided colon, the left-sided colon or the middle/low rectum. The efficacy of first-line and non-first-line anti-EGFR treatment was analysed. Genomic differences in colorectal cancer data from The Cancer Genome Atlas (TCGA) were investigated and visualised with OncoPrint and a clustered heatmap.ResultsOn first-line anti-EGFR treatment, patients with middle/low rectal tumours had significantly lower progression-free survival, overall survival, and overall response rates (6.8 months, 27.8 months and 43%, respectively) than those with left-sided colon cancer (10.1 months, 38.3 months and 66%, respectively). Similar outcomes were also identified on non-first-line anti-EGFR treatment. In TCGA analysis, rectal tumours displayed genetic heterogeneity and shared features with both left- and right-sided colon cancer.ConclusionsAnti-EGFR treatment has lower efficacy in metastatic middle/low rectal cancer than in left-sided colon cancer.

Atypical, Non-V600 BRAF Mutations as a Potential Mechanism of Resistance to EGFR Inhibition in Metastatic Colorectal Cancer.

Atypical, non-V600 BRAF (aBRAF) mutations represent a rare molecular subtype of metastatic colorectal cancer (mCRC). Preclinical data are used to categorize aBRAF mutations into class II (intermediate to high levels of kinase activity, RAS independent) and III (low kinase activity level, RAS dependent). The clinical impact of these mutations on anti-EGFR treatment efficacy is unknown. Data from 2,084 patients with mCRC at a single institution and from an external cohort of 5,257 circulating tumor DNA (ctDNA) samples were retrospectively analyzed. Overall survival (OS) was calculated using Kaplan-Meier and log-rank tests. Statistical tests were two-sided. BRAF mutations were harbored by 257 patients, including 36 with aBRAF mutations: 22 class III, 10 class II, four unclassified. For patients with aBRAF mCRC, median OS was 36.1 months, without a difference between classes, and median OS was 21.0 months for patients with BRAFV600E mCRC. In contrast to right-sided predominance of tumors with BRAFV600E mutation, 53% of patients with aBRAF mCRC had left-sided primary tumors. Concurrent RAS mutations were noted in 33% of patients with aBRAF mCRC, and 67% of patients had microsatellite stable disease. Among patients with aBRAF RAS wild-type mCRC who received anti-EGFR antibodies (monotherapy, n = 1; combination therapy, n = 10), no responses to anti-EGFR therapy were reported, and six patients (four with class III aBRAF mutations, one with class II, and one unclassified) achieved stable disease as best response. Median time receiving therapy was 4 months (range, 1 to 16). In the ctDNA cohort, there was an increased prevalence of aBRAF mutations and subclonal aBRAF mutations (P < .001 for both) among predicted anti-EGFR exposed compared with nonexposed patients. Efficacy of anti-EGFR therapy is limited in class II and III aBRAF mCRC. Detection of aBRAF mutations in ctDNA after EGFR inhibition may represent a novel mechanism of resistance.

Changes in KRAS mutations in patients with oral mucosa and tongue cancer (OMTC) undergoing medical treatment with cetuximab (Cet).

e17524 Background: Mutations in KRAS are known to be predictors of anti-EGFR therapy efficacy. Besides the mutation status of the treatment-naive tumors the changes in the level of mutant DNA during medical treatment are also of clinical interest for the individualization of the treatment. The purpose of the study was to detect somatic single nucleotide polymorphism (SNP) activating mutations in KRAS exon 2 in patients (pts) with OMTC undergoing chemotherapy (CT)±Cetuximab (Cet). Methods: Extracellular DNA samples were obtained from plasma of pts with OMTC (T3-4No-1Mo) undergoing CT (CDDP+5FU)+Cet (group A) before treatment and in 2 weeks after. Patients undergoing CT (CDDP+5FU, no Cet) were included in Group B. 7 activating mutations in KRAS exon 2 were detected by Droplet Digital PCR method (DD PCR) with "KRAS Screening Multiplex Kit" (BioRad, USA). Results: Samples from 28 pts were included. The frequency of SNP activating in KRAS exon 2 before treatment was 25%. In the group A (n = 12) KRAS mutations were not found or the level of mutant DNA did not exceed 1%. No significant changes were found in this group after treatment. The group B (n = 16) had some KRAS variations the majority of which did not change after treatment. However, 2 pts had a sharp increase in mutant DNA: from 0.03% before CT in both cases to 17.04% and 56.38% -after treatment (p &lt; 0.01). Conclusions: Medical treatment, especially CT, could cause the changes in activating mutations in KRAS exon 2 in pts with OMTC. Revealing of these changes is of great importance for the following treatment options. Detection of mutant extracellular DNA by DD PCR could be valuable to monitor their status during the treatment.

Abstract P5-17-06: Immune modulation with humanized anti-EGFR antibody panitumumab in an immunocompetent mouse model for inflammatory breast cancer

Abstract Background: Inflammatory breast cancer (IBC) is the most lethal and aggressive form of breast cancer and there are no approved targeted therapies specifically for IBC. Targeting the epidermal growth factor receptor (EGFR) pathway is a promising therapeutic target for patients with triple-negative IBC (TN-IBC) with a reported pathological complete response rate of 42% (JAMA Oncology, 2018). The tumor microenvironment (TME) is a critical contributor to the aggressiveness of IBC. Delineating cross-talk between EGFR-targeted therapies and TME components, which define IBC, could inform more efficient combination regimens and novel clinical trial designs for IBC. However, such studies have not been conducted due to the lack of a syngeneic IBC mouse model. Here we report the establishment of an IBC immunocompetent mouse model and the effects of panitumumab (PmAb) on IBC tumor growth and the TME. Methods: TN-IBC cell lines, SUM149 or FC-IBC-02, were mixed with 50% Matrigel and inoculated into mammary fat pads of hu-NSG-SGM3 mice engrafted with hematopoietic stem cells (The Jackson Laboratory). SUM149 tumor growth in hu-NSG-SGM3 mice treated with either IgG2 (isotype control, 4 mg/kg) or PmAb (1 mg/kg and 4 mg/kg) was measured. The percentages of TME components, including human CD4+ T, CD8+ T, regulatory T (Tregs), and natural killer (NK) cells, and M1 or M2 macrophages, in the peripheral blood and tumor tissues treated with IgG2 and PmAb for 7 weeks were measured by flow cytometry. Results: Hu-NSG-SGM3 mice supported the growth of TN-IBC SUM149 and FC-IBC-02 xenografts. These humanized mouse models were named SUM149-huSGM3 and FC-IBC-02-huSGM3, respectively. Analysis of the blood cells showed that SUM149-huSGM3 mice display human CD4+ T, CD8+ T, Tregs, M1 and M2 macrophages. T cell infiltration and M1 and M2 macrophages were also detected in SUM149-huSGM3 tumors. NK cells were not detected in both peripheral blood and tumors. PmAb treated SUM149-huSGM3 mice had significantly reduced SUM149 tumor growth, compared with mice that received the IgG2 control. PmAb treatment increased the percentage of CD8+ T cells and reduced the percentage of Tregs in peripheral blood. A similar analysis of tumor infiltrating lymphocytes isolated from each group showed an increase in percent CD8+ T cells in mice treated with PmAb. There were no significant changes of M1 or M2 macrophages following PmAb treatment. These results suggest that the increase in percentage of CD8+ T cells in peripheral blood and IBC tumors, and the decrease in percentage of Tregs in peripheral blood may contribute to the therapeutic efficacy of PmAb. Conclusion: We established the first immunocompetent mouse model to study the TME and immune response in IBC, which provides the premise for conducting a diversity of novel preclinical therapeutic studies. The mechanism of how immune responses of TN-IBC xenografts mediates the therapeutic efficacy of PmAb in IBC tumors needs to be further investigated. Our study also suggests that combination therapy with immune checkpoint inhibitors may potentiate the efficacy of anti-EGFR therapy in IBC. The therapeutic efficacy of PmAb and anti-PD-L1 combination in SUM149 humanized mice is in progress. Citation Format: Wang X, Shao S, Pearson T, Cheng Y, Reuben JM, Tripathy D, Ueno NT. Immune modulation with humanized anti-EGFR antibody panitumumab in an immunocompetent mouse model for inflammatory breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-17-06.

Clinicopathological features, efficacy of anti-EGFR therapy, and survival outcomes in patients with BRAF non-V600 mutated metastatic colorectal cancer.

659 Background: BRAF non-V600 mutations occur in 2-3% of colorectal cancer. These mutants can be classified as RAS independent (class 2) or RAS dependent (class 3). We reported BRAF non-V600 mutations could be a negative predictive factor for anti-EGFR therapy in patients (pts) with pretreated metastatic colorectal cancer (mCRC), while mCRC pts with class 3 BRAF mutations could respond to anti-EGFR therapy because of its dependency on receptors and RAS. Methods: This study evaluates the efficacy to anti-EGFR therapy in a large cohort of pts with BRAF non-V600 mutated mCRC. Pts with mCRC referred to the participating centers from 2010 to 2017 were included. Clinicopathological features, efficacy of anti-EGFR therapy, and survival outcomes were stratified by BRAF mutational class. Results: One hundred seventeen pts with BRAF non-V600 mutated mCRC were identified. Median age was 58 years (range, 27-83), 68 pts (58%) were male, and 38 pts (33%) had right-sided tumors. Mucinous histology was seen in 11 cases (9%); concurrent RAS mutations occurred in 31 cases (27%), and 3 cases (3%) were MSI-H. Also, TP53 mutations were detected in 74 pts among 90 analyzed cases (82%). Regarding BRAF mutation subtype, 25/63/29 pts were classified as class 2/3/not reported (NR), respectively. Median OS in RAS wild-type/mutant were 44.8/34.6 months, respectively (p=0.082). The median OS in RAS wild-type pts with BRAF non-V600 mutations for class 2, 3, and NR were 25.7, 44.2, and 79.1 months, respectively (class 2 vs. 3, p=0.219). Among 40 pts treated with anti-EGFR therapy, response rates were 14%, 44%, and 40% for class 2, 3, and NR, respectively. Median PFS was 4.4, 8.3, 4.0 months for class 2, 3, and NR, respectively. Moreover, in 25 pts receiving anti-EGFR therapy as third or later line, response rate was 0%, 27%, and 50% in class 2, 3, and NR, and median PFS was 2.8, 3.7, and 4.0 months (p=0.762), respectively. Conclusions: Pts with class 2 BRAF mutations tend to have a poor prognosis compared to those with class 3 mutations. While almost half of pts with class 3 BRAF mutations responded to anti-EGFR therapy, response was rare for pts with class 2 BRAF mutations, and none achieved objective response in the third or later line.

Activity of EGFR inhibition in atypical (non-V600E) BRAF-mutated metastatic colorectal cancer.

596 Background: Atypical BRAF mutations (a BRAF) represent a rare molecular subtype of metastatic colorectal cancer (mCRC), distinct from BRAFV600E (class I). Preclinical data categorizes a BRAF into class II (intermediate-high kinase activity without RAS dependency) and III (low kinase activity, RAS dependent), however the clinical impact regarding these functional classes is unknown. Methods: We retrospectively analyzed 2,084 mCRC patients (pts) at MD Anderson Cancer Center (MDACC) to identify a BRAF and BRAFV600E. Clinicopathologic features were compared by chi-square or fisher’s exact test. Overall survival (OS) calculated utilizing Kaplan-Meier method and log-rank test. Statistical tests were two-sided. Results: a BRAF occurred in 36 mCRC pts (1.7%; 95% CI 1.2-2.4): 22 class III, 10 class II, 4 unclassified. The most common class II and class III BRAF codons were 469 (60%) and 594 (59%), respectively . Median OS (mOS) for a BRAF mCRC was 39.4 months (mo), without difference between class III and II. 19/36 (53%) were left sided primary tumors and 24/36 (67%) were microsatellite stable. BRAFV600E occurred in 221 mCRC pts (10.6%; 95% CI 9.3-12.0) with a mOS of 21.0 mo. In contrast to BRAFV600E which is mutually exclusive with RAS mutations, 12 pts with a BRAF were RAS mutants (class III, 7/21 [33%], class II 5/10 [50%]). Among a BRAF RAS wt pts, 11 (50%) received anti-EGFR monoclonal antibodies (mAb) (class III 7/14 [50%], class II 3/5 [60%]). There were no responses, and only three pts (all class III) achieved stable disease as best response. Median time on therapy was 4 months. Class II RAS wt pts treated with anti-EGFR mAb had mOS of 31.7 mo versus 46.8 mo for those not exposed (HR 2.0; 95% CI 0.3-15.9). Class III RAS wt pts treated with anti-EGFR mAB had mOS of 44.2 mo versus 45.7 mo for those not treated (HR 0.80; 95% CI 0.2-2.6). Conclusions: a BRAF mCRC appear to manifest improved clinical outcomes as previously reported. Despite this, the efficacy of anti-EGFR therapy appears limited in class II and III patients. Future efforts are needed to establish the predictive impact of functional classes on anti-EGFR efficacy and to design novel therapeutic strategies for a BRAF mCRC.

EGFR Protein Expression of KRAS Wild-Type Colorectal Cancer: Predictive Value of the Sidedness for Efficacy of Anti-EGFR Therapy.

Right- and left-sided colorectal cancers (RSCRC and LSCRC, respectively) are different developmentally, genetically and prognostically. Clinical data also indicate that they respond differently to anti-EGFR therapies. The role of EGFR protein expression in KRAS wild type colorectal cancer is also controversial. Here we have used a cohort of anti-EGFR antibody treated KRAS-wild type colorectal cancer patients (n = 97) to analyse the prognostic role of EGFR protein expression in relation to sidedness. In our cohort EGFR copy number, determined by FISH, was not associated with the level of EGFR protein, assessed by immunohistochemistry and measured by H-scoring. There was a significantly higher EGFR H-score detected in RSCRC as compared to LSCRC in primary tumors (p = 0.04). Furthermore, in a proportion of cases (n = 31) metastatic tissues were also available and their analysis also found a significantly higher EGFR H-score in metastases of RSCRC compared to LSCRC (p = 0.018). Kaplan Meyer survival analysis demonstrated that anti-EGFR antibody therapies were more effective in case of LSCRC compared to RSCRC. Although in case of progression-free survival data just indicated a trend (p = 0.065), in case of overall survival the difference was significant favouring LSCRC (p = 0.047). These data demonstrated for the first time that the EGFR protein expression is significantly higher in KRAS wild type RSLCL as compared to LSCRC. Meanwhile it is somewhat unexpected that the lower EGFR protein expression was found to be associated with better efficacy of anti-EGFR antibody therapies of colorectal cancer, the finding of which must be further validated.

PET Imaging Biomarkers of Anti-EGFR Immunotherapy in Esophageal Squamous Cell Carcinoma Models.

Epidermal growth factor receptor (EGFR) is overexpressed and considered as a proper molecular target for diagnosis and targeted therapy of esophageal squamous cell carcinoma (ESCC). This study evaluated the usefulness of PET imaging biomarkers with 64Cu-PCTA-cetuximab and 18F-FDG-PET for anti-EGFR immunotherapy in ESCC models. In vivo EGFR status and glucose metabolism by cetuximab treatment were evaluated using 64Cu-PCTA-cetuximab and 18F-FDG-PET, respectively. Therapeutic responses with imaging biomarkers were confirmed by western blot and immunohistochemistry. TE-4 and TE-8 tumors were clearly visualized by 64Cu-PCTA-cetuximab, and EGFR expression on TE-8 tumors showed 2.6-fold higher uptake than TE-4. Tumor volumes were markedly reduced by cetuximab in TE-8 tumor (92.5 ± 5.9%), but TE-4 tumors were refractory to cetuximab treatment. The SUVs in 64Cu-PCTA-cetuximab and 18F-FDG-PET images were statistically significantly reduced by cetuximab treatment in TE-8 but not in TE-4. 64Cu-PCTA-cetuximab and 18F-FDG-PET images were well correlated with EGFR and pAkt levels. 64Cu-PCTA-cetuximab immuno-PET had a potential for determining EGFR level and monitoring therapeutic response by anti-EGFR therapy. 18F-FDG-PET was also attractive for monitoring efficacy of anti-EGFR therapy. In conclusion, PET imaging biomarkers may be useful for selecting patients that express target molecules and for monitoring therapeutic efficacy of EGFR-targeted therapy in ESCC patients.

Clinical Significance of BRAF Non-V600E Mutations in Colorectal Cancer: A Retrospective Study of Two Institutions

BackgroundRecent advances in next-generation sequencing have enabled the detection of BRAF V600E mutations as well as BRAF non-V600E mutations in a single assay. The present work aimed to describe the clinicopathological characteristics and clinical outcome of the BRAF non-V600E mutant-type in colorectal cancer (CRC). Patients and methodsCRC samples from 111 Stage IV patients were analyzed for somatic mutations using a 415-gene comprehensive genomic sequencing panel. Patients were classified according to BRAF status as wild-type, V600E mutant-type, or non-V600E mutant-type. Differences between clinicopathological characteristics and genetic alterations were analyzed among the three groups. Overall survival (OS) and the response to anti-EGFR therapy were also analyzed. ResultsComprehensive genomic sequencing revealed that 98 patients (88%), 7 patients (6%), and 6 patients (6%) were wild-type, V600E mutant-type, and non-V600E mutant-type, respectively. Non-V600E mutant-type tumors were frequently left-sided (83%), while V600E mutant-type tumors were frequently right-sided (86%; P = 0.025). Non-V600E mutant-type showed better OS than V600E mutant-type (P = 0.038), with no significant difference compared with wild-type tumors. The two patients with non-V600E mutations who underwent repeated metastasectomies showed no evidence of disease at final follow-up. Regarding the efficacy of anti-EGFR therapy, the patient with an I326V mutation had progressive disease (+115%) despite no genetic alterations detected in the EGFR pathway that could drive resistance, suggesting an alternate resistance mechanism. ConclusionsNon-V600E mutant-type is more likely to be left-sided and demonstrates better OS than V600E mutant-type. Further preclinical and clinical investigations are needed to clarify the role of non-V600E mutations in CRC.

Abstract 3705: Targeting interleukin-1 to increase cetuximab efficacy in head and neck cancer

Abstract Treatment for head and neck squamous cell carcinoma (HNSCC) patients includes the epidermal growth factor receptor (EGFR) monoclonal antibody cetuximab. However, response to cetuximab is low and resistance remains a critical issue. Therefore, it is imperative to develop strategies to enhance tumor response to this drug. Inflammation plays an important role in tumor progression by increasing the release of cytokines that promote tumor cell survival. Our prior work has shown that a variety of pro-inflammatory cytokines involved in tumor survival are upregulated upon treatment with EGFR inhibitors in HNSCC cells, suggesting that poor tumor response to EGFR inhibitors may be due to increased tumor-associated inflammation. Our lab has shown that the increased proinflammatory tumor response due to EGFR inhibition may be activated by interleukin-1 (IL-1) signaling, suggesting that the IL-1 pathway may be an important target to enhance the efficacy of anti-EGFR therapy. Here we investigated the effect of IL-1 blockade on HNSCC tumor response to cetuximab treatment. We found that cetuximab induced IL-6 secretion from SQ20B HNSCC cells and knockdown of the adapter protein MyD88, which is essential for IL-1 signaling, suppressed IL-6 secretion at baseline and in response to cetuximab treatment. Similarly, knock down of the IL-1 receptor (IL-1R) decreased baseline and cetuximab-induced IL-6 secretion, although IL-1R knockdown did not improve response to cetuximab in SQ20B xenografts in vivo. We additionally blocked IL-1 signaling using a recombinant IL-1R antagonist (IL-1RA). IL-1RA pre-treatment reduced baseline and cetuximab-induced IL-6 secretion in vitro. Although IL-1RA did not significantly enhance SQ20B tumor response to cetuximab, IL-1RA as a single agent significantly suppressed tumor growth in female mice but not in male mice. Finally, treatment with a human-specific neutralizing IL-1 alpha (IL-1α) antibody (but not IL-1 beta (IL-1β)) reduced baseline and cetuximab-induced IL-6 secretion in vitro, and significantly increased SQ20B tumor response to cetuximab in vivo. Altogether we propose that targeting IL-1α specifically may be a viable strategy to improve HNSCC tumor response to cetuximab. Citation Format: Madelyn Espinosa-Cotton, Ayana J. McLaren, Adam T. Koch, Andrean L, Simons. Targeting interleukin-1 to increase cetuximab efficacy in head and neck cancer [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 3705. doi:10.1158/1538-7445.AM2017-3705

Association of CpG island methylator phenotype and EREG/AREG methylation and expression in colorectal cancer.

Background:High EREG and AREG expression, and left-sided primary tumours are associated with superior efficacy of anti-epidermal growth factor receptor (EGFR) therapy in metastatic colorectal cancer (CRC), but a unifying explanation of these findings is lacking.Methods:RNA-seq, gene expression arrays, and DNA methylation profiling were completed on 179 CRC tumours. Results were validated using independent The Cancer Genome Atlas data sets. An independent cohort of 198 KRAS wild-type metastatic CRC tumours was tested for CpG island methylator phenotype (CIMP) status, and progression-free survival (PFS) with the first anti-EGFR regimen was retrospectively determined.Results:EREG and AREG expression was highly inversely correlated with methylation and was inversely associated with right-sided primary tumour, BRAF mutation, and CIMP-high status. Treatment of CRC cell lines with hypomethylating agents decreased methylation and increased expression of EREG. Inferior PFS with anti-EGFR therapy was associated with CIMP-high status, BRAF mutation, NRAS mutation, and right-sided primary tumour on univariate analysis. Among known BRAF/NRAS wild-type tumours, inferior PFS remained associated with CIMP-high status (median PFS 5.6 vs 9.0 mo, P=0.023).Conclusions:EREG and AREG are strongly regulated by methylation, and their expression is associated with CIMP status and primary tumour site, which may explain the association of primary tumour site and EREG/AREG expression with anti-EGFR therapy efficacy.

Genomic profiling and efficacy of anti-EGFR therapy in appendiceal adenocarcinoma.

Genomic profiling and efficacy of anti-EGFR therapy in appendiceal adenocarcinoma.

Impact of first-line bevacizumab therapy on the efficacy of subsequent anti-epidermal growth factor antibodies (anti-EGFR) in metastatic colorectal cancer (mCRC).

685 Background: The FIRE3 study reported that cetuximab added to first line combination chemotherapy versus the addition of bevacizumab to the same chemotherapy backbone, with a planned switch to the alternative biologic in second line therapy, resulted in improved overall survival. One possible explanation is that the sequence of biologic administration in mCRC impacts on treatment benefit. Examination of the efficacy of anti-EGFR therapy in cohorts where patients have and have not received prior bevacizumab will inform this. Methods: We interrogated our prospective database (ACCORD), which records comprehensive detail on demographics, treatments received and patient outcomes for consecutive mCRC patients in real world practice across multiple institutions in Australia. We included patients receiving 2nd and subsequent line anti-EGFR monotherapy. Disease control rate (DCR) (partial response plus stable disease), progression free survival (PFS) and overall survival (OS) from the start of anti-EGFR were determined as a function of prior bevacizumab use. Results: From a total of 1511 patients treated between 01/10/2002 and 31/12/2014,129 patients treated with single agent anti- EGFR were identified, 75 had received prior bevacizumab. Demographics, performance status and tumour characteristics were similar between the 2 groups. 84% were confirmed KRAS exon 2 wild type. Prior treatment with bevacizumab did not impact DCR (35% vs 40%, p = 0.5065), median PFS (3.0 vs 3.0 months, p = 0.9460) or OS (8.6 vs 8.4 months, HR 0.95, p = 0.8073). Similarly, for bevacizumab treated patients, the time since last dose of bevacizumab to start of anti-EGFR ( &lt; 3 months (n = 26) vs 3-6 months (n = 17) vs &gt; 6 months (n = 32)) did not impact PFS (2.3 vs 3.6 vs 3 months) or OS (8.9 vs 10.1 vs 7.1 months, HR: 0.88, p = 0.82). Conclusions: There was no evident impact of previous bevacizumab treatment, or time from previous bevacizumab treatment, on the efficacy of single agent anti-EGFR therapy in a routine clinical practice cohort. Our data do not support the notion that prior bevacizumab renders tumors more or less sensitive to subsequent anti EGFR therapy.

Genomic profiling and efficacy of anti-EGFR therapy in appendiceal adenocarcinoma.

574 Background: Metastatic appendiceal adenocarcinoma (AAC) is a heterogenous disease and the majority of patients present with diffuse metastases in the peritoneal cavity. Cytotoxic and targeted therapies are typically extrapolated from colorectal adenocarcinoma (CRC), however, it is not known whether this is effective or not. Herein we investigated the genetic profiles of these tumors in an effort to identify molecular characteristics and potentially actionable mutations, as well as the response to anti-EGFR therapy in RAS/BRAF wild type (wt) AAC. Methods: We identified patients (pts) with ACC treated at MSKCC who had tumor who had undergone molecular profiling, either by next generation sequencing using our MSK-IMPACT platform, or by MALDI-TOF mass spectroscopy genotyping (Sequenom). MSK-IMPACT tumors and matched normal samples were analyzed either on 410 gene panel. Sequenom (provided an 8 gene panel including KRAS, NRAS, BRAF, and PIK3CA). Via an IRB approved waiver, we collected tumor histology and evaluated pts who were RAS/RAF wt and had been treated with anti-EGFR therapy. Results: We identified a total 97 AAC pts, of whom 60 had Sequenom testing and 37 had IMPACT. Among pts analyzed with IMPACT, 24 had mucinous adenocarcinoma, 3 adenocarcinoma with signet ring, 7 adenocarcinoma ex goblet cell carcinoid, 3 invasive adenocarcinoma. In total 159 alterations were identified with a median 4.2 alterations/patient (range 0-10). Alterations were seen most commonly in KRAS (21/37), GNAS (12/37), TP53 (10/37), SOX9 (5/37), and SMAD4 (4/37). Potentially treatable alterations were present in 15% of patients and included BRAF V600E (1), MTOR (2), ERBB2 (1) and NTRK(2). Of the total 97 pts, 50 (52%) were RAS/BRAF wt. Of those,13 evaluable patients received anti-EGFR therapy with either panitumumab or cetuximab. There were no responders. Conclusions: Mutational sequencing in AAC indicates that 16% have mutations in genes such as BRAFV600E, MTOR, ERBB2 and NTRK with the potential to expand investigational options through increased access to trials of selectively targeted agents. Additionally, in RAS/BRAF wt pts, panitumumab/cetuximab does not appear to have therapeutic efficacy comparable to historic controls in RAS/RAF wt CRC.

Does bevacizumab impact anti-EGFR therapy efficacy in metastatic colorectal cancer?

Anti-EGFR therapy and antiangiogenic therapies are used alone or in combination with chemotherapies to improve survival in metastatic colorectal cancer. However, it is unknown whether pretreatment with antiangiogenic therapy could impact on the efficacy of anti-EGFR therapy.We selected one hundred and twenty eight patients diagnosed with advanced colorectal cancer with a KRAS and NRAS unmutated tumor. These patients were treated with cetuximab or panitumumab alone or with chemotherapy as second or third-line. Univariate and multivariate Cox model analysis were performed to estimate the effect of a previous bevacizumab regimen on progression free survival and on overall survival during anti-EGFR therapy. In vitro studies using wild type KRAS and NRAS colon cancer cells were performed to evaluate the impact of VEGF-A on cetuximab-induced cell death.The median progression free survival (PFS) during anti-EGFR treatment was significantly different between the bevacizumab group and the non-bevacizumab group (2.8 and 4 months respectively; p = 0.003). The median overall survival from the beginning of the metastatic disease was similar in the two groups (41.3 and 42 months respectively; p = 0.7). In vitro, VEGF-A induced a resistance toward cetuximab cytotoxicity on three KRAS and NRAS wild type colon cancer cell lines in a VEGFR2 and Stat-3-dependent manner.All in all, our clinical data, supported by in vitro procedures, suggest that a previous anti-VEGF therapy decreases anti-EGFR efficacy. Although these results are observed in a limited cohort, they could be taken into consideration for a better strategy of care for patient suffering from metastatic colorectal cancer.

Gene-expression profiles correlate with the efficacy of anti-EGFR therapy and chemotherapy for colorectal cancer.

Comprehensive gene-expression analysis is very useful for classifying specific cancers into subgroups on the basis of their biological characteristics; it is used both prognostically and predictively. The purpose of this study was to classify unresectable advanced or recurrent colorectal cancer (CRC) by gene-expression profiling of formalin-fixed paraffin-embedded tissues and to correlate CRC subgroups with clinicopathological and molecular features and clinical outcomes. One hundred patients with advanced or recurrent CRC were enrolled. RNA extracted from FFPE tissues was subjected to gene-expression microarray analysis. The patients were stratified into four subgroups (subtypes A1, A2, B1, and B2) by unsupervised hierarchical clustering. By use of principle-components analysis (PCA), the patients were divided into subtypes A and B on the basis of component 1 and into subtypes 1 and 2 on the basis of component 2. Subtype A was significantly enriched among patients without the KRAS mutation and with an earlier clinical stage at diagnosis. With regard to anti-EGFR therapy, progression-free survival (PFS) was better for patients in subtype A without the KRAS mutation than for those with the KRAS mutation (P = 0.047). PFS for patients without the KRAS mutation in subtype B was comparable with that for patients with the KRAS mutation (P = 0.55). Similar results were observed in a validation set. We found that gene-expression profiles enabled stratification of CRC patients into four subgroups. The efficacy of anti-EGFR therapy was correlated with component 1 from PCA. This comprehensive study may explain the heterogeneity of unresectable advanced or recurrent CRC and could be useful for identifying novel biomarkers for CRC treatment.

The nationwide genomic screening project for gastrointestinal cancer in Japan (GI-SCREEN): Simultaneous identification of KRAS, NRAS, BRAF, and PIK3CA mutation in advanced colorectal cancer (aCRC) (GI-SCREEN 2013-01).

578 Background: Recent studies confirmed that minor KRAS or NRAS mutations are associated with the resistance to anti-EGFR therapy for advanced colorectal cancer (aCRC). Although the impact of BRAF or PIK3CA mutation on efficacy of anti-EGFR therapy is still controversial, targeting agents for these mutations are under developing. Efficient screening systems for these relatively minor mutations with short turnaround time are necessary for the successful development of targeted therapies. Methods: This study was initiated in February 2014 as one of new nationwide genomic screening projects for advanced gastrointestinal cancer patients in Japan. Patients with aCRC who are planned to receive systemic chemotherapy were eligible. A total of 36 mutations of KRAS codon 61, 146, NRAS codon 12, 13, 61, BRAF codon 600, PIK3CA codon 542, 545, 546 and 1047 in genomic DNA of cancer cells were simultaneously analyzed at a quality-controlled central laboratory using Luminex (xMAP) technology in a single reaction using 50 ng of DNA. Results: As of August 31, 2014, this study is ongoing with the participation of 16 major cancer centers in Japan. A total of 437 aCRC patients were enrolled to this study and 361 tumor samples has been analyzed with success rate for genomic analysis of 100%. Among the 237 patients with KRAS exon 2 wild type, 28 patients (11.8%) had other RAS mutations and 15 patients (6.3%) had BRAF mutation. Twenty-seven of 437 patients had PIK3CA mutations (6.2%). One patient with BRAF mutation was enrolled in early clinical trials of BRAF inhibitors in combination with anti-EGFR antibody and most of other patients are still treated with standard chemotherapies, which may become future candidates for early clinical trials. Conclusions: From our preliminary results, this nationwide screening system enabled to detect rare mutations using limited amounts of samples from aCRC, which may facilitate the enrollment of patients in IND registration trials for targeted therapies as well as optimal individualized treatment.

ET-45 * KNOCKDOWN OF TNFSF13B INDUCES GLIOMA STEM CELL APOPTOSIS

Tumor Necrosis Factor (Ligand) Super Family member 13B (TNFSF13B; BAFF) is primarily produced by myeloid lineage cells, activated T cells and dendritic cells, and up-regulates anti-apoptotic Bcl-2 family proteins. Approximately 20% of glioblastoma overexpress TNFSF13B, which may account for treatment resistance. A Kaplan-Meier curve from a query of The Cancer Genome Atlas (TCGA) showed that glioblastoma patients with increased expression (EXP > 2) of TNFSF13B have a significantly shorter overall survival (P = 0.025). By immunoblotting, TNFSF13B expression was differentially expressed in a panel of glioma stem cells (GSCs). GFP-tagged TNFSF13B shRNA lentivirus was used to knock down TNFSF13B in multiple cell lines. Erlotinib or lapatinib inhibited cell viability to a greater extent in shTNFSF13B cells compared to scramble control. After 1 µM erlotinib treatment for 3 days, cell viability was suppressed by 34% in shTNFSF13B GSC11 cells compared to scramble control cells. Lapatinib (0.1 µM for 3 days) reduced cell viability by 40% in shTNFSF13B GSC11 cells compared to controls. Apoptosis, assessed by Annexin V-based flow cytometry, revealed a 30% increase in Annexin V staining after erlotinib treatment (1 µM for 3 days) in shTNFSF13B GSC11 cells compared with controls. The level of anti-apopototic proteins BCL-XL and Bid markedly decreased which was concomitant with an increase in cleaved caspase 9 in shTNFSF13B cells treated with EGFR inhibitors. Using an apoptosis protein array, we observed that anti-apoptotic proteins Bcl-2, survivin, claspin and HIF-1α significantly decreased in shTNFSF13B cells compared with scramble cells after treatment of 1 µM erlotinib. Ongoing in vivo studies are validating the impact of targeting TNFSF13B in a glioma xenograft model. Our studies identified TNFSF13B as a potentially important mediator of glioma stem cell survival in vitro and suggest that TNFSF13B may be a potential therapeutic target to enhance the efficacy of anti-EGFR therapy.