Antibodies In Metastatic Colorectal Cancer Research Articles

Combined amphiregulin and epiregulin expression as a prognostic and predictive biomarker of panitumumab (Pmab), fluorouracil, and folinic acid (FU/FA) or FU/FA maintenance therapy following Pmab+FOLFOX induction in RAS wildtype metastatic colorectal cancer (mCRC): PANAMA trial (AIO-KRK-0212).

3528 Background: mRNA expression of amphiregulin ( AREG) and epiregulin ( EREG) as ligands of the epidermal growth factor receptor (EGFR) were associated with response to anti-EGFR directed antibodies in metastatic colorectal cancer (mCRC). Their role for maintenance treatment remained unclear yet and was investigated in the PanaMa trial (panitumumab (Pmab) and fluorouracil/folinic acid (FU/FA) vs. FU/FA alone after Pmab+FOLFOX induction therapy in RAS wild-type mCRC). Methods: Gene expression was measured after mRNA isolation in 196 of 248 patients of the full analysis set. The analysis was conducted using a customized Nanostring PanCancer Progression Panel. AREG and EREG mRNA expression was dichotomized by median. High combined expression was defined as mRNA expression of AREG and EREGequal or above the median. Median progression-free (PFS) and overall survival (OS) since start of maintenance were estimated by Kaplan-Meier-method and Cox-regression, using the log rank test. Objective response rates (ORR) of maintenance therapy were compared by Fisher’s exact test. Treatment interaction was tested by Cox regression. Results: In 196 patients with available mRNA expression data, high AREG, EREG and combined AREG / EREG expression were observed in 103 (52.6%), 97 (49.5%) and 84 (42.9%), respectively. Regardless of treatment, high combined AREG / EREG expression was associated with prolonged PFS (7.7 vs. 5.8 months, HR 0.69 (95% CI 0.51 – 0.93), P=0.016), OS (30.1 vs. 24.4 months, HR 0.58 (95% CI 0.41 – 0.82), P=0.002) and increased ORR of maintenance treatment (39.3% vs. 28.6%, P=0.13), compared to low expression. Tumors with high combined AREG / EREG expression were associated with numerical longer PFS, OS and higher ORR when treated with Pmab+FU/FA maintenance (Table). Significant interaction of combined AREG / EREG expression with treatment was observed in terms of PFS ( P=0.003) and OS ( P=0.016). Conclusions: Combined AREG and EREG mRNA expression was confirmed as prognostic biomarker for mCRC patients receiving maintenance treatment. Efficacy of maintenance treatment might potentially be higher for Pmab+FUFA maintenance in mCRC with high combined AREG / EREG expression in the PanaMa trial. [Table: see text]

Clinical utility of serial circulating tumor DNA (ctDNA) to identify acquired resistance to anti-EGFR antibodies in metastatic colorectal cancer (mCRC).

158 Background: Real-world evidence informing on the value of incorporating serial ctDNA into clinical practice is lacking. We aimed to explore the utility of serial ctDNA for identifying mechanisms of resistance and new targets for patients (pts) receiving anti-EGFR therapy for mCRC. Methods: We retrospectively reviewed 2801 pts with mCRC who had ≥1 alteration detected on a Guardant360 assay (Guardant Health) and subsequently had serial ctDNA assessments with known intervening therapies. We compared detection of new MAPK pathway alterations ( RAS/EGFR/BRAFV600 SNV or indel, MET or ERBB2 amplification) among patients who initially lacked these alterations by whether patients received anti-EGFR antibody alone (panitumumab or cetuximab), in combination with chemotherapy, or if they had never received an anti-EGFR antibody between ctDNA assays. Patients with a subsequent ctDNA assay after therapy initiation were included for analysis of acquired alterations. Results: Of 2801 pts, 1308 (47%) harbored ≥1 MAPK alteration in their first ctDNA timepoint and were excluded from analysis. Of the remaining 1493 without a MAPK alteration prior to therapy, 588 (39.4%) had a MAPK alteration detected in a subsequent ctDNA timepoint. Among 447 of 1493 pts (31.8%) with subsequent exposure to anti-EGFR antibodies, acquisition of a MAPK alteration occurred in 229/447 (51.2%). This was more common (OR 2.01. 95% CI 1.61-2.51, P<0.0001) than in patients without exposure to anti-EGFR antibodies (359/1046 [34.3%]). Acquired MAPK alterations were more common among those receiving single agent antibodies (42/66, 63.6%) than anti-EGFR plus chemotherapy (187/381, 49.1%) (OR 1.82, 95% CI 1.05-3.08, P=0.030). Patients with anti-EGFR antibody exposure were found to have higher blood TMB scores in the first assay after treatment compared to patients treated with chemotherapy alone (11.5 vs. 8.8 mut/MB, respectively; P=0.001), with no significant blood TMB difference between those receiving single agent anti-EGFR versus anti-EGFR plus chemotherapy (median 12.4 vs. 11.5 mut/MB; P=0.52). Patients who acquired MAPK alterations after anti-EGFR therapy had higher blood TMB scores compared to patients who did not acquire MAPK alterations (median 14.3 vs 8.6 mut/MB, respectively; p<0.0001). Conclusions: In this large cohort of pts with mCRC and treatment information, we demonstrate serial ctDNA identified a large proportion of patients acquiring resistance alterations that may impact response to future therapies. These results suggest serial ctDNA analysis may provide additional molecular insights for patients receiving anti-EGFR therapy and inform future anti-EGFR rechallenge strategies.

Impact of acquired RAS, BRAF and PIK3CA mutation at 8 weeks on the efficacy of anti-EGFR monoclonal antibodies in metastatic colorectal cancer.

193 Background: Recent studies indicate that the emergence of RAS/BRAF mutation sometimes occurs during initial anti-EGFR monoclonal antibody (mAb)-based treatment in metastatic colorectal cancer (mCRC). However, limited data was available regarding the timing and frequency of the emergence of RAS/BRAF mutation, and its impact on the efficacy of anti-EGFR mAb. With this background, we conducted an observational study to monitor RAS, BRAF, and PIK3CA mutation status by ctDNA in RAS/BRAF wt mCRC. Methods: RAS-trace is a pilot study to monitor RAS, BRAF, and PIK3CA mutation status by ctDNA, using NGS-based Plasma-Safe-SeqS technology for RAS/BRAF wt (diagnosed from tissue samples) mCRC treated with anti-EGFR mAb as a first-line chemotherapy. ctDNA- RAS/BRAF/PIK3CA status evaluated at baseline, 8, 12, 16, 20, 24, 36, 48 weeks and disease progression. The primary endpoint was the time to the acquired RAS mutations. The results of ctDNA at baseline and 8 weeks are presented. Results: Forty-two patients were enrolled, and 40 and 39 were used in the analysis of ctDNA at baseline and 8 weeks, respectively. All patients received mFOLFOX6 plus cetuximab (N=32) or panitumumab (N=8). At baseline, RAS, BRAF, and PIK3CA mutations were detected in 3, 3, and 1 of the 40 patients, respectively. One patient had both KRAS and BRAF mutations. Baseline ctDNA mutations were not associated with the presence of liver metastases, tumor sidedness, early tumor shrinkage, depth of response or skin rash ≥Grade 2. At 8 weeks, RAS, BRAF, and PIK3CA mutations were detected in 3, 2, and 0 among the 39 patients, respectively. One patient had both KRAS and BRAF mutations. ctDNA mutations at 8 weeks were not associated with the presence of liver metastases, tumor sidedness, or early tumor shrinkage, however, they were associated with depth of response and had a tendency of skin rashes ≥ Grade 2 (Table). Conclusions: Emergence of RAS/BRAF/PIK3CA mutations at 8 weeks may be related to the response of anti-EGFR mAb. The association of ctDNA status with survival outcomes will be presented in 2025. Clinical trial information: jRCT1050210160 . [Table: see text]

P-387 Rechallenge with anti-EGFR antibodies in metastatic colorectal cancer: A single center analysis

P-387 Rechallenge with anti-EGFR antibodies in metastatic colorectal cancer: A single center analysis

Upfront vs deferred monoclonal antibodies in metastatic colorectal cancer: A target trial emulation using the GEMCAD 14-01 prospective cohort.

3597 Background: There are no randomized trials comparing the addition monoclonal antibodies (MAB: bevacizumab, cetuximab, panitumumab) to first line chemotherapy (upfront use) versus deferring their addition to the second-line chemotherapy (deferred use) in pts with metastatic colorectal cancer (mCRC). We emulated a target trial comparing upfront vs deferred use of MAB using the GEMCAD 14-01 observational registry. Methods: We first specified the (hypothetical) target trial to fully articulate the research question and then emulated it using real-world data. The eligibility criteria of the target trial were a diagnosis of mCRC, being treatment naïve, and a ECOG PS <2. The target trial would randomize pts to the following strategies: (1) initiation of MAB within 2 months of starting first line chemotherapy (“upfront MAB”) and (2) initiation of MAB within 2 months of starting second line chemotherapy (“deferred MAB”). The primary outcome of the target trial would be overall survival and the causal contrast (or estimand) would be the effect under complete adherence. We emulated this target trial using data from the GEMCAD 1401 registry (ClinicalTrials.gov identifier: NCT02254941), which collected data prospectively from 47 Spanish centers from June 2014 to June 2018. The emulation used the same definitions of eligibility criteria and treatment strategies, and classified individuals according to their baseline data using clones. The effect under complete adherence was estimated by censoring pts when they deviated from the assigned treatment strategy and by using time-varying weights to adjust for baseline and post-baseline confounding. Results: A total of 627 pts were eligible in the ‘’upfront MAB’’ and 397 pts in the ‘’deferred MAB’’. Median age was in the ‘’upfront vs deferred’’ 64.6 (interquartile range: 56-71) vs 67.8 (61-75) years, 96% vs 87% had an ECOG 0-1, 80% vs 79% had a Charlson score < 3, 46% vs 60% had a RAS mutation, 6% vs 4% had a BRAF mutation, 72% vs 69% had left side primary location, 74% in both strategies had liver metastasis and 42% vs 50% had LDH levels above the normal threshold. Pts in the “upfront MAB” group contributed a total 16,057 months of follow-up and 502 if them died. Pts in the “deferred MAB” contributed a total of 7,774 months of follow-up, and 222 of them died. The 48-month overall survival was 26.7% (95% CI 21.4-38.2%) in the “upfront MAB” group and 21.6% (14.2-41.7%) in the “deferred MAB” group, corresponding to a 48-month survival difference (“upfront MAB” is the reference) of -5.0% (95% CI -17.9 to 17.95) and a hazard ratio or 1.15 (0.88-1.40). Conclusions: Our study suggests little or no survival detrimental effect of deferring the use of MAB to the second line of treatment compared with the use of MAB as part of the first line of treatment among pts with mCRC. Clinical trial information: NCT02254941 .

Negative Ultraselection of Patients With RAS/BRAF Wild-Type, Microsatellite-Stable Metastatic Colorectal Cancer Receiving Anti-EGFR-Based Therapy.

PURPOSESeveral uncommon genomic alterations beyond RAS and BRAFV600E mutations drive primary resistance to anti–epidermal growth factor receptors (EGFRs) in metastatic colorectal cancer (mCRC). Our PRESSING panel (including PIK3CA exon 20/AKT1/PTEN mutations, ERBB2/MET amplifications, gene fusions, and microsatellite instability-high status) represented a paradigm of negative hyperselection with more precise tailoring of EGFR blockade. However, a modest proportion of hyperselected mCRC has intrinsic resistance potentially driven by even rarer genomic alterations.MATERIALS AND METHODSA prospective data set at three Italian Academic Hospitals included 650 patients with mCRC with comprehensive genomic profiling by FoundationOne CDx and treated with anti-EGFRs. PRESSING2 panel alterations were selected on the basis of previous clinico-biologic studies and included NTRKs, ERBB3, NF1, MAP2K1/2/4, AKT2 pathogenic mutations; PTEN/NF1 loss; ERBB3, FGFR2, IGF1R, KRAS, ARAF, and AKT1-2 amplification; and EGFR rearrangements. These were collectively associated with outcomes in patients with hyperselected disease, ie, RAS/BRAF wild-type, PRESSING-negative, and microsatellite stable.RESULTSAmong 162 hyperselected patients, 24 (15%) had PRESSING2 alterations, which were mutually exclusive except in two samples and were numerically higher in right-sided versus left-sided cancers (28% v 13%; P = .149). Independently of sidedness and other factors, patients with PRESSING2-positive status had significantly worse progression-free survival and overall survival compared with PRESSING2-negative ones (median progression-free survival 6.4 v 12.8 months, adjusted hazard ratio 4.19 [95% CI, 2.58 to 6.79]; median overall survival: 22.6 v 49.9 months, adjusted hazard ratio 2.98 [95% CI, 1.49 to 5.96]). The combined analysis of primary tumor sidedness and PRESSING2 status allowed us to better stratify outcomes.CONCLUSIONNegative ultraselection warrants further investigation with the aim of maximizing the benefit of EGFR blockade strategies in patients with RAS and BRAF wild-type, microsatellite stable mCRC.

Economic Evaluation of Monoclonal Antibodies in Metastatic Colorectal Cancer: A Systematic Review.

Colorectal cancer (CRC) is one of the major causes of mortality and morbidity worldwide. The median overall survival (OS) of patients with metastatic CRC (mCRC) has doubled over the last 20 years partly due to the introduction of advanced biologic therapies. However, these treatment modalities bear significant costs on healthcare systems globally, and may jeopardize their fiscal sustainability. The aim of this systematic review was to critically appraise the economic evaluations of monoclonal antibodies in mCRC. A literature search was performed in the electronic databases of: Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects, EMBASE, EMBASE Alert, PUBMED, NHS Economic Evaluation and Health Technology Assessment Database for full articles published from 1 January 2013 to 31 December 2020. Twenty economic analyses were identified in the literature that fulfilled the inclusion criteria and evaluated the cost-effectiveness of (a) bevacizumab as first-line treatment for mCRC and as maintenance treatment, (b) cetuximab as first-line treatment, (c) panitumumab versus bevacizumab and cetuximab versus bevacizumab as first-line treatment, (d) aflibercept and ramucirumab as second-line treatment, (e) cetuximab and panitumumab as third-line treatment, (f) cetuximab versus panitumumab as later lines of treatment, and (g) RAS testing prior to anti-epidermal growth factorreceptor (EGFR) treatment. Bevacizumab in combination with chemotherapy is cost-effective as neither first-line treatment nor maintenance treatment. Sequential treatment with bevacizumab in first-line and second-line treatment was also not cost-effective. Testing for KRAS and extended RAS mutations is cost-effective and should be performed prior to anti-EGFR treatment. In the RAS wild-type subgroup of mCRCs the use of anti-EGFR (panitumumab or cetuximab) in first-line treatment leads to a more favorable cost-effectiveness profile than the corresponding anti-VEGF (bevacizumab). Cetuximab is not cost-effective as a first-line treatment. Anti-EGFR administration is not a cost-effective strategy in third-line treatment, even for RAS wild-type mCRCs, compared to best supportive care. Aflibercept was superior to ramucirumab and costed less, but neither were cost-effective compared to standard care.

CtDNA-based mutational landscape following anti-EGFR antibodies in metastatic colorectal cancer (mCRC) to uncover novel resistance mechanisms in the CCTG CO.26 trial.

117 Background: Previous studies have identified MAPK and PIK3CA/AKT/mTOR pathways as common mechanisms of acquired resistance to anti-EGFR antibodies (EGFRab) in mCRC. However, such alterations do not account for all patients that become treatment resistant. Using paired whole-exome (WES; tissue) and circulating tumor DNA (ctDNA; plasma) sequencing, we performed characterization of the EGFRab resistance landscape in patients with mCRC. Methods: Post-treatment (ctDNA; plasma) sequencing was performed for 169 patients with mCRC, with 112 (66%) patients also receiving pre-treatment (WES; primary tumor) sequencing as part of the CO.26 trial. 66 (39%) patients received EGFRab previously at a median of 132.0 days prior to plasma sampling. Using bespoke bioinformatics pipelines (WES) coupled with the GuardantOMNI assay (plasma), we compared somatic mutation (SNV/indel, CNV and fusion) frequencies between pre- and post-EGFRab timepoints, and contrasted results between the two groups. Results: Significant increases in de novo acquisition of EGFR (p = 5.6e-4), KRAS (p = 0.011), ZNF217 (p = 0.0022), MAP2K1 (p = 0.0078) and LRP1B (p = 0.017) SNV/indels were unique to the EGFRab group and often occurred as multiple, low allele frequency events in the same patient. De novo copy number amplification of known resistance genes EGFR/ BRAF/ MET were observed in EGFRab-treated patients (p < 0.05), along with SMO (p = 6.8e-7), PTEN inhibitory gene PREX2 (p = 5.6e-4), FLT3 (p = 2.0e-5), NOTCH4 (p = 6.3e-5), ERBB2 (7.4e-4), KMT2A (p = 3.7e-4) and ARID1B (p = 0.0014). Genes impacted by fusion events in EGFRab-treated patients included BRAF-KIAA1549 (1 patient) and MET-CAV1 (1 patient), and these events were not detected in matched pre-treatment samples. EGFRab-treated patients were found to acquire a combination of multiple (≥5) mutation events (SNV/indel, CNV or fusion) at much higher frequency compared to non-EGFRab-treated patients (67% versus 25% of patients, p = 8.7e-8). Tumor mutation burden (TMB) was not significantly different (p = 0.71) between treatment groups prior to therapy initiation, while post-treatment TMB was significantly higher (p = 1.8e-7) in EGFRab-treated patients (median 25.4 versus 13.1 mut/mb). Conclusions: In addition to previously established resistance pathways, we identified acquired alterations in additional genes such as SMO, PREX2 and epigenetic modifiers KMT2A/ARID1B in EGFRab-treated patients . Moreover, we highlight the phenomenon by which EGFRab-treated tumors acquire multiple concurrent resistance mutations and heightened TMB. Our analysis provides novel insight into the landscape of resistance mechanisms to EGFRab in mCRC while highlighting the potential role for immunotherapy post-EGFRab. Clinical trial information: NCT02870920.

A Critical Review of Second-Generation Anti-EGFR Monoclonal Antibodies in Metastatic Colorectal Cancer.

Anti-EGFR monoclonal antibodies (mAbs) have become a relevant solution for the treatment of patients with metastatic colorectal cancer. Current anti-EGFR monoclonal antibodies face a series of problems, including resistance and non-durable response, and RAS and BRAF mutations serve as exclusion criteria for treatment with anti-EGFR mAbs. Advances in molecular tumor profiling and information on subsequent pathways responsible for disease progression and drug resistance helped develop a new generation of anti-EGFR mAbs. These second-generation mAbs have been developed to overcome existing resistance mechanisms and to limit common side effects. For the moment, existing literature suggests that these novel anti-EGFR mAbs are far from finding their way to clinical practice soon. In this review, we summarize and evaluate current data regarding ongoing research and completed clinical trials for different second-generation anti-EGFR monoclonal antibodies. Anti-EGFR mAbs exhibit efficacy in advanced colorectal cancer, but second-generation mAbs failed to prove their benefit in the treatment of metastatic colorectal cancer. Understanding the biological basis of primary and acquired drug resistance could allow scientists to design better clinical trials and develop improved second-generation mAbs.

RAS status in circulating-tumor DNA (ctDNA) and outcomes during rechallenge treatments with anti-EGFR antibodies in metastatic colorectal cancer (mCRC).

166 Background: We have evaluated rechallenge treatment with irinotecan plus cetuximab (JACCRO CC-08, n = 36) or panitumumab (JACCRO CC-09, n = 25) in patients (pts) with KRAS wild-type mCRC [Tsuji A, WCGC 2018], and the primary endpoint of PFS rate at 3 months was met in both trials. RAS status in ctDNA may potentially predict responders of the rechallenge treatment in mCRC resistant to anti-EGFR antibody [Cremolini C, JAMA Oncol 2018]. Methods: A post-hoc biomarker study was performed to investigate an association between RAS status in ctDNA and clinical outcomes in the JACCRO phase II trials comprised mCRC pts who achieved a clinical benefit from 1st-line anti-EGFR antibody-based therapy, then had a disease progression at 2nd-line treatment. RAS status in ctDNA was analyzed at the time points of baseline, 8 weeks, and progression using OncoBEAM RAS CRC Kit for specific KRAS/ NRAS mutations, using cut-off value defined as the number of beads with amplified-mutant molecules specifically set per each codon. Results: Sixteen pts (median 67.5-y old, 50% of PS0, 25% of right-sided primary, cet/pani: 4/12) were enrolled in this study, with response rate of 0% and disease control rate (DCR) of 62.5%. RAS mutations (mt) were found at the baseline in 6 out of 16 pts (all left-sided pts with KRAS codon 12, codon 61 and/or NRAS codon 61 mt simultaneously). Pts without RAS mt at baseline experienced longer PFS in 1st-line treatment (11.5 vs. 9.0 m). The DCR was 33% in pts with RAS mt in ctDNA, while it was 80% in pts without RAS mt at baseline. Pts with RAS mt at baseline had significantly shorter PFS and OS than pts without RAS mt [median PFS 2.3 vs 4.7 m, HR 6.2 (95%CI 1.6-30.5), p = 0.013; median OS 3.8 vs. 16.0 m, HR 12.4 (95%CI 2.7-87.7), p = 0.0028]. Six of 10 pts without RAS mt at baseline acquired RAS mt ( KRAS/ NRAS codon 12 or 61) in ctDNA at progression, however there was no difference in survival between pts with/without RAS mt at progression. Conclusions: Our study demonstrated that RAS status in ctDNA using OncoBEAM RAS CRC Kit predicts survival of rechallenge treatment with anti-EGFR antibody in mCRC pts. These data can support the application of RAS monitoring into clinical practice. Clinical trial information: UMIN000015914/UMIN000015916.

Previous Bevacizumab and Efficacy of Later Anti–Epidermal Growth Factor Receptor Antibodies in Metastatic Colorectal Cancer: Results From a Large International Registry

BackgroundThe FIRE-3 [5-fluorouracil, folinic acid, and irinotecan (FOLFIRI) plus cetuximab versus FOLFIRI plus bevacizumab in first line treatment colorectal cancer (CRC)] study reported that first-line FOLFIRI plus cetuximab versus FOLFIRI plus bevacizumab resulted in similar progression-free survival (PFS) but improved overall survival (OS). A potential explanation is that the initial biologic agent administered in metastatic CRC (mCRC) affects later line efficacy of the other treatments. We sought to test this hypothesis. Materials and MethodsWe interrogated our mCRC registry (Treatment of Recurrent and Advanced Colorectal Cancer) regarding treatment and outcome data for RAS wild-type patients receiving epidermal growth factor receptor inhibitors (EGFRIs) in second and subsequent lines. Survival outcomes from the beginning of EGFRI use were determined as a function of previous bevacizumab use and the interval between ceasing bevacizumab and beginning EGFRI use. ResultsOf 2061 patients, 222 eligible patients were identified, of whom 170 (77%) had received previous bevacizumab and 52 (23%) had not. PFS and OS from the start of EGFRIs did not differ by previous bevacizumab use (3.8 vs. 4.2 months; hazard ratio [HR], 1.12; P = .81; 9.0 vs. 9.2 months; HR, 1.19; P = .48, respectively) for the whole cohort or when analyzed by the primary tumor side (HR for left side, 1.07; P = .57; HR for right side, 1.2; P = .52). PFS was significantly shorter with right-sided primary tumors when the interval between bevacizumab and EGFRI use was < 6 versus > 6 months (median, 2.2 vs. 6 months; HR, 2.23; P = .01) but not with left-sided tumors (median, 4.2 vs. 5.5 months; HR, 1.12; P = .26). ConclusionPrevious bevacizumab use had no effect on the activity of subsequent EGFRIs. The apparent effect of time between biologic agents in right-sided tumors might reflect patient selection.

Plasticity of Resistance and Sensitivity to Anti-Epidermal Growth Factor Receptor Inhibitors in Metastatic Colorectal Cancer.

Colorectal cancer (CRC) is one of the most prevalent cancers and the second leading cause of cancer mortality worldwide. Survival in the metastatic setting has been gradually improved by the addition to cytotoxic chemotherapy of agents targeting the vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR). Considerable heterogeneity exists within CRC due to the varied genetic and epigenetic mechanisms involved in differing pathways of carcinogenesis. The knowledge of molecular abnormalities underlying colorectal tumourigenesis and the progression of dysplastic precursors to invasive and ultimately metastatic lesions has advanced in recent years by comprehensive sequencing studies. From these genome-scale analyses, we know that a handful of genes are commonly affected by somatic mutations, whereas recurrent copy-number alterations and chromosomal translocations are rarer in this disease. Even though some of these molecular abnormalities make genes acting as drivers of cancer progression, translation of this recognition for therapeutic purposes is still limited, encompassing only as standard of care the exclusion of RAS-mutated cancers for better selecting patients to candidate to EGFR-targeted therapy with monoclonal antibodies. However, the effort of ameliorating molecular selection should not be considered exhausted by demonstration of RAS and BRAF-induced resistance, as the genomic landscape of response to EGFR blockade has been demonstrated to be wider and dynamically multifaceted. In this chapter we will review main molecular biomarkers of de novo (primary) and acquired (secondary) resistance to EGFR-targeted monoclonal antibodies in metastatic CRC and discuss therapeutic implications.

Prognostic role of the LCS6 KRAS variant in locally advanced rectal cancer: results of the EXPERT-C trial

Lethal-7 (let-7) is a tumour suppressor miRNA which acts by down-regulating several oncogenes including KRAS. A single-nucleotide polymorphism (rs61764370, T > G base substitution) in the let-7 complementary site 6 (LCS-6) of KRAS mRNA has been shown to predict prognosis in early-stage colorectal cancer (CRC) and benefit from anti-epidermal growth factor receptor monoclonal antibodies in metastatic CRC. We analysed rs61764370 in EXPERT-C, a randomised phase II trial of neoadjuvant CAPOX followed by chemoradiotherapy, surgery and adjuvant CAPOX plus or minus cetuximab in locally advanced rectal cancer. DNA was isolated from formalin-fixed paraffin-embedded tumour tissue and genotyped using a PCR-based commercially available assay. Kaplan-Meier method and Cox regression analysis were used to calculate survival estimates and compare treatment arms. A total of 155/164 (94.5%) patients were successfully analysed, of whom 123 (79.4%) and 32 (20.6%) had the LCS-6 TT and LCS-6 TG genotype, respectively. Carriers of the G allele were found to have a statistically significantly higher rate of complete response (CR) after neoadjuvant therapy (28.1% versus 10.6%; P = 0.020) and a trend for better 5-year progression-free survival (PFS) [77.4% versus 64.5%: hazard ratio (HR) 0.56; P = 0.152] and overall survival (OS) rates (80.3% versus 71.9%: HR 0.59; P = 0.234). Both CR and survival outcomes were independent of the use of cetuximab. The negative prognostic effect associated with KRAS mutation appeared to be stronger in patients with the LCS-6 TT genotype (HR PFS 1.70, P = 0.078; HR OS 1.79, P = 0.082) compared with those with the LCS-6 TG genotype (HR PFS 1.33, P = 0.713; HR OS 1.01, P = 0.995). This analysis suggests that rs61764370 may be a biomarker of response to neoadjuvant treatment and an indicator of favourable outcome in locally advanced rectal cancer possibly by mitigating the poor prognosis of KRAS mutation. In this setting, however, this polymorphism does not appear to predict cetuximab benefit.

Prognostic significance of K-Ras mutation rate in metastatic colorectal cancer patients.

Activating mutations of K-Ras gene have a well-established role as predictors of resistance to anti-EGFR monoclonal antibodies in metastatic colorectal cancer (mCRC) patients. Their prognostic value is controversial, and no data regarding the prognostic value of mutation rate, defined as the percentage of mutated alleles/tumor sample, are available. We aimed to evaluate the prognostic value of K-Rasmutation rate in a homogenous cohort of mCRC patients receiving first-line doublet plus bevacizumab. This retrospective study enrolled 397 K-Ras mutant mCRC patients from 6 Italian centers, and 263 patients were fully evaluable for our analysis. K-Ras mutation rate was assessed by pyrosequencing. Patients with less than 60% of cancer cells in tumor tissue were excluded. No patients received anti-EGFR containing anticancer therapy, at any time. Median mutation rate was 40% and was adopted as cut-off. The primary and secondary endpoints were PFS and OS respectively. At univariate analysis, K-Ras mutation rate higher than 40% was significantly associated with lower PFS (7.3 vs 9.1 months; P < 0.0001) and OS (21 vs 31 months; P = 0.004). A multivariate model adjusted for age at diagnosis, site of origin of tumor tissue (primary vs metastases), referral center, number of metastatic sites, and first-line chemotherapy backbone, showed that K-Ras mutation rate remained a significant predictor of PFS and OS in the whole population. Our data demonstrate an association between K-Ras mutation rate and prognosis in mCRC patients treated with bevacizumab-containing first-line therapy. These data deserve to be verified in an independent validation set.

Early tumor shrinkage and depth of response predict long-term outcome in metastatic colorectal cancer patients treated with first-line chemotherapy plus bevacizumab: results from phase III TRIBE trial by the Gruppo Oncologico del Nord Ovest

Early tumor shrinkage (ETS) and depth of response (DoR) predict overall survival (OS) in first-line trials of chemotherapy ± anti-EGFR monoclonal antibodies in metastatic colorectal cancer (mCRC). These associations and the predictive accuracy of response measurements for survival parameters were investigated in the phase III TRIBE trial of FOLFOXIRI plus bevacizumab (bev) versus FOLFIRI plus bev. A landmark approach was adopted to define the assessable population. The distribution of RECIST response rate, ETS and DoR was compared in the two arms. Associations between response measurements and progression-free survival (PFS), post-progression survival (PPS) and OS were tested by univariate and multivariate Cox models. Prediction performance of each factor was estimated by C-index. A significantly higher percentage of patients in the FOLFOXIRI plus bev arm achieved ETS ≥20%, when compared with the control arm (62.7% versus 51.9%, P = 0.025). Also the DoR was significantly higher in the triplet plus bev arm (43.4% versus 37.8%, P = 0.003). Both ETS and DoR were associated with PFS, PPS and OS at the univariate analyses and in the multivariate models stratified for other prognostic variables. Both ETS and DoR were able to predict survival as accurately as RECIST response. FOLFOXIRI plus bev improves ETS and DoR when compared with FOLFIRI plus bev. Achieving rapid and deep tumor shrinkage consistently delays tumor progression and prolongs survival in patients treated with first-line chemotherapy plus bev. ETS is a promising and valuable end point for clinical trials' design deserving further investigation.

Hazard ratio-based model weighing values of regorafenib and monoclonal antibodies in metastatic colorectal cancer.

e14506 Patients with wild type (WT) KRAS metastatic colorectal cancer (mCRC) treated with 1st-line cetuximab (Cet) or bevacizumab (Bev) and chemotherapy demonstrated similar overall survival (OS) (...

Anti-epidermal growth factor receptor monoclonal antibodies in metastatic colorectal cancer: a meta-analysis.

To investigate the correlation between Kirsten rat sarcoma viral oncogene homolog (KRAS) status and the therapeutic effects of anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (MoAbs) in metastatic colorectal cancer (mCRC). Randomized controlled trials (RCTs) were identified and the association between KRAS mutation and clinical outcome in mCRC patients treated with anti-EGFR MoAbs was investigated. Ten RCTs were included in this meta-analysis. Progression-free survival and overall survival were used to assess the strength of the relationship between KRAS mutation and clinical outcome. In first-line treatment, survival benefit was confined to patients with wild-type KRAS. Chemotherapy regimens and angiogenesis inhibitor treatment influenced the results of the analysis. Wild-type KRAS mCRC patients did not seem to benefit from oxaliplatin-based chemotherapy (PFS: HR = 0.88, 95%CI: 0.70-1.10; OS: HR = 0.93, 95%CI: 0.82-1.04). Clinical benefit in mCRC patients was limited to therapeutic regimens which included anti-EGFR MoAbs and fluorouracil-based therapy (PFS: HR = 0.77, 95%CI: 0.69-0.86; OS: HR = 0.85, 95%CI: 0.75-0.95). When anti-EGFR MoAbs were used as second- or further-line treatment, clinical benefit was still confined to patients with wild-type KRAS. KRAS status is a potential predictive marker of clinical benefit due to anti-EGFR MoAb therapy in mCRC patients.

Impact of genetic profiles on the efficacy of anti-EGFR antibodies in metastatic colorectal cancer with KRAS mutation.

Reports indicate that, even in KRAS-mutated colon cancer, there are subsets of patients who benefit from anti-EGFR monoclonal antibody (MoAb) treatment. The aim of the present study was to identify genetic profiles that contribute to the responsiveness of metastatic colorectal cancer (mCRC) to anti-EGFR MoAb. We retrospectively evaluated the efficacy of anti-EGFR MoAb in mCRC patients with KRAS mutations according to KRAS mutational subtypes, BRAF and PIK3CA mutational status and PTEN and MET expression. Among 21 patients with KRAS-mutant tumors, 8 (38%) harbored p.G13D, 7 (33%) harbored p.G12V, 5 (24%) harbored p.G12D, and 1 (5%) harbored p.G12C mutation. Patients with the p.G13D mutation exhibited a significantly higher disease control rate than patients with other KRAS mutations (P=0.042), and tended to show a longer progression-free survival (PFS) than patients with other KRAS mutations with marginal significance (P=0.074). Patients with loss of PTEN had significantly shorter PFS than those with normal PTEN expression in patients with KRAS mutations (P=0.044). MET overexpression was significantly associated with shorter PFS compared to normal MET expression in patients with KRAS mutations (P=0.016). Our data demonstrated the potential utility of alterations in PTEN and MET expression as predictive markers for response to anti-EGFR MoAbs in mCRC patients with KRAS mutations. In addition, we confirmed the predictive value of the KRAS p.G13D mutation for better response to anti-EGFR therapies in comparison with other KRAS mutations.

RAS mutations and cetuximab in locally advanced rectal cancer: Results of the EXPERT-C trial

BackgroundRAS mutations predict resistance to anti-epidermal growthfactor receptor (EGFR) monoclonal antibodies in metastatic colorectal cancer. We analysed RAS mutations in 30 non-metastatic rectal cancer patients treated with or without cetuximab within the 31 EXPERT-C trial. MethodsNinety of 149 patients with tumours available for analysis were KRAS/BRAF wild-type, and randomly assigned to capecitabine plus oxaliplatin (CAPOX) followed by chemoradiotherapy, surgery and adjuvant CAPOX or the same regimen plus cetuximab (CAPOX-C). Of these, four had a mutation of NRAS exon 3, and 84 were retrospectively analysed for additional KRAS (exon 4) and NRAS (exons 2/4) mutations by using bi-directional Sanger sequencing. The effect of cetuximab on study end-points in the RAS wild-type population was analysed. ResultsEleven (13%) of 84 patients initially classified as KRAS/BRAF wild-type were found to have a mutation in KRAS exon 4 (11%) or NRAS exons 2/4 (2%). Overall, 78/149 (52%) assessable patients were RAS wild-type (CAPOX, n=40; CAPOX-C, n=38). In this population, after a median follow-up of 63.8months, in line with the initial analysis, the addition of cetuximab was associated with numerically higher, but not statistically significant, rates of complete response (15.8% versus 7.5%, p=0.31), 5-year progression-free survival (75.5% versus 67.5%, hazard ratio (HR) 0.61, p=0.25) and 5-year overall survival (83.8% versus 70%, HR 0.54, p=0.20). ConclusionsRAS mutations beyond KRAS exon 2 and 3 were identified in 17% of locally advanced rectal cancer patients. Given the small sample size, no definitive conclusions on the effect of additional RAS mutations on cetuximab treatment in this setting can be drawn and further investigation of RAS in larger studies is warranted.

From KRAS mutations to RAS mutations: Towards a better definition of response to anti-EGFR antibodies in metastatic colorectal cancer

L’identification des mutations de KRAS comme facteur prédictif de résistance aux anticorps anti-EGFR a permis de faire un grand pas dans la personnalisation du traitement du cancer colorectal métastatique. Récemment, la recherche d’autres mutations au niveau des gènes de la famille RAS a fait la preuve de son intérêt dans l’identification des patients pouvant tirer bénéfice de ces anticorps anti-EGFR. Parallèlement, des travaux plus fondamentaux ont permis de mieux comprendre les mécanismes de résistance secondaire aux anticorps anti-EGFR et d’envisager, à court ou moyen terme, la recherche des mutations de KRAS ou de RAS au niveau du sang périphérique.