RAS Mutant mCRC Research Articles

Efficacy of anti-epidermal growth factor antibody rechallenge in RAS/BRAF wild-type metastatic colorectal cancer: a multi-institutional observational study

PurposeTo investigate circulating tumor DNA (ctDNA) RAS mutant (MT) incidence before salvage-line treatment and the clinicopathological features and molecular biological factors associated with the efficacy of anti-epithelial growth factor receptor (EGFR) monoclonal antibody (mAb) rechallenge for tissue RAS/BRAF wild type (WT) metastatic colorectal cancer (mCRC).MethodsThis multi-institutional retrospective observational study included 74 patients with mCRC with tissue RAS/BRAF WT refractory to first-line chemotherapy containing anti-EGFR mAb. ctDNA RAS status was assessed using the OncoBEAM™ RAS CRC Kit. We explored the clinicopathological features associated with ctDNA RAS status and the factors related to anti-EGFR mAb rechallenge efficacy in multivariate Cox proportional hazard regression.ResultsThe incidence of RAS MT in ctDNA was 40.5% (30/74), which was associated with primary tumor resection (P = 0.016), liver metastasis (P < 0.001), and high tumor marker levels (P < 0.001). Among the 39 patients treated with anti-EGFR mAb rechallenge, those with ctDNA RAS WT showed significantly longer progression-free survival (PFS) than those with ctDNA RAS MT (median 4.1 vs. 2.7 months, hazard ratio [HR] = 0.39, P = 0.045). Patients who responded to first-line anti-EGFR mAb showed significantly longer PFS (HR = 0.21, P = 0.0026) and overall survival (OS) (HR = 0.23, P = 0.026) than those with stable disease.ConclusionsThe incidence of ctDNA RAS MT mCRC was 40.5%, which was associated with liver metastases and high tumor volumes. Anti-EGFR mAb rechallenge may be effective for patients with mCRC who responded to first-line chemotherapy containing anti-EGFR mAb. No patients with RAS MT in ctDNA responded to anti-EGFR mAb rechallenge.

A phase II clinical trial of metformin combined with FOLFIRI plus bevacizumab as second-line therapy in patients with RAS-mutant metastatic colorectal cancer.

3534 Background: Metastatic colorectal cancer (mCRC) patients with RAS mutations are confronted with limited novel targeted therapy. We previously reported that KRAS mutation mediated MATE1 down-regulation sensitizes colorectal cancer cells to metformin. Based on our preclinical research, we designed a study to explore whether metformin combined with FOLFIRI plus bevacizumab would improve efficacy in RAS mutant mCRC. Methods: This single-arm, multicenter trial (ChiCTR2000037943) recruited patients with RAS mutant mCRC that had failed to first-line bevacizumab plus an oxaliplatin-based regimen of systemic therapies. Patients received metformin 1000mg PO twice daily on day 1-14, plus irinotecan 180 mg/m² IV, calcium folinate 400 mg/m² IV, fluorouracil 400 mg/m² IV, and a 46-h CIV of fluorouracil 2400 mg/m², and bevacizumab 5 mg/kg IV, repeated every 14 days. We used Simon's two-stage design. The primary endpoint was objective response rate (ORR). The secondary endpoints were disease control rate (DCR), progression-free survival (PFS), overall survival (OS) and safety. Results: One hundred sixteen patients were recruited between July 2020 and March 2023. KRAS codon 12 mutations were present in 81 cases (69.8%), codon 13 mutations in 17 cases (14.7%), codon 61 mutations in 6 cases (5.2%), and codon 146 mutations in 3 cases (2.6%). For the 81 patients with KRAS codon 12 mutation, 42 were with G12D (51.9%), 21 with G12V (25.9%), 7 with G12A (8.6%), and 6 with G12C (7.4%) mutation. The ORR was 21.6% (25/116), and DCR was 76.7% (89/116). The median PFS was 8.0 months, and patients without liver metastasis had longer PFS than those with liver metastasis (9.5 months vs. 5.6 months, P &lt; 0.001). For the 45 patients without liver metastasis, the administration of metformin combined with FOLFIRI plus bevacizumab as second-line therapy resulted in significantly longer PFS than the first-line bevacizumab plus an oxaliplatin-based regimen (9.5 months vs. 7.9 months, P = 0.037). The median OS was not reached. The most common treatment-emergent adverse events (TEAEs) were neutropenia (73.7%), nausea (56.9%), anemia (54.3%) and diarrhea (49.1%). Grade 3 and above TEAEs occurred in 52 (44.8%) patients. No treatment-related mortality occurred. Conclusions: Metformin combined with FOLFIRI and bevacizumab had promising efficacy and tolerable toxicity in RAS mutant mCRC patients as second-line therapy. Further study in phase 3 trials is warranted. Clinical trial information: ChiCTR2000037943.

Temporal dynamics of RAS mutations in circulating tumor DNA in metastatic colorectal cancer: clinical significance of mutation loss during treatment

PurposeIn metastatic colorectal cancer (mCRC), RAS mutation loss may occur during the standard-of-care regimen. In this study, we aimed to investigate the temporal dynamics of the RAS gene and its clinical significance.MethodsThis was a retrospective, single-center study that included 82 patients with tissue RAS-mutant (RAS-MT) mCRC who underwent circulating tumor DNA (ctDNA) RAS monitoring between January, 2013–April, 2023. Patients were analyzed for the rate of change over time to acquired RAS mutation loss (aRAS-ML) and clinicopathological factors. The prognostic relevance of mutation loss was assessed.ResultsaRAS-ML was detected in 33 (40.2%) patients, 32 of whom had a mutation loss in the first ctDNA RAS assay. Patients with a RAS mutation detected in the first assay had a median time of 8 months until the second ctDNA RAS assay, with 4.5% cases newly converted to aRAS-ML; no new conversions were detected at the third assay. The aRAS-ML group exhibited more single-organ metastases in the target organ during ctDNA measurement (aRAS-ML: 84.8% vs. RAS-MT: 59.2%, p = 0.02). Of the 33 patients with aRAS-ML, seven (21.2%) received anti-epidermal growth factor receptor (EGFR) therapy, with a median progression-free survival of 8 months. Multivariate analysis revealed that persistent ctDNA RAS mutation was an independent prognostic factor for overall survival (hazard ratio: 2.7, 95% confidence interval: 1.1–6.3, p = 0.02).ConclusionThe rate of ctDNA mutation loss in patients with RAS-MT mCRC decreases over time. Therefore, using a ctDNA RAS assay early in treatment will assist in challenging the use of EGFR regimens.

NeoRAS wild-type metastatic colorectal cancer in the SCRUM-Japan GOZILA study.

3506 Background: The ’’Neo RAS’’ phenomenon refers to RAS mutant (MT) metastatic colorectal cancer (mCRC) that becomes RAS wild-type (WT) following treatment. This Neo RAS WT population might represent a novel indication for EGFR inhibitors, which are less effective in RAS MT mCRC. The incidence and clinicopathological characteristics of Neo RAS WT mCRC using plasma cell-free DNA (cfDNA) next generation sequencing has not been defined. Methods: As part of a large-scale nationwide screening platform (SCRUM-Japan GOZILA), 478 patients with an initial diagnosis of RAS MT mCRC by tissue analysis (MEBGEN RASKET-B) who received systemic therapy underwent cfDNA testing (Guardant 360) prior to later lines of treatment. Based on the cfDNA results, we evaluated the clinicopathological characteristics of those with Neo RAS WT and RAS MT. Neo RAS WT was defined as no RAS MT ( KRAS or NRAS) detected in plasma and was assessed in the overall cohort (Cohort A) and in the subgroup with at least one somatic alteration detected in plasma (Cohort B) to exclude those with insufficient tumor DNA shedding. Results: Median age at the time of blood sampling was 62.0 years old, and 257 (51.9%) were men. 160 (32.3%) and 319 (64.4%) had right-sided tumors and multi-organ metastases. The lungs were the most frequent site of metastasis (60.2%), followed by liver (57.4%), lymph nodes (28.9%), and peritoneum (28.5%). The prevalence of Neo RAS WT was 19.0% (91/478) in Cohort A and 9.8% (41/429) in Cohort B. The frequency of Neo RAS WT in tumors originally with KRAS exon 2 MT tended to be lower than in those with other RAS MT (18.1% vs 25.4%, P = 0.21 in Cohort A, 9.0% vs 15.4%, P = 0.14 in Cohort B). There were significant differences in the prevalence of Neo RAS WT between patients with single organ vs multi-organ metastases (P &lt; 0.001 in Cohort A, P = 0.004 in Cohort B), absence vs presence of liver metastasis (P &lt; 0.001 in both Cohort A and B), lymph node metastasis (P = 0.006 in Cohort A), peritoneal metastasis (P = 0.002 in group A), and bone metastasis (P = 0.029 in Cohort A), testing immediately prior to 2nd through to 4th line treatment vs later lines (P = 0.007 in Cohort A), immediate prior use of regorafenib (P = 0.027 in Cohort A) and any history of vascular endothelial growth factor inhibitors (P = 0.003 in Cohort A, P = 0.035 in Cohort B). In the logistic regression multivariate analysis, absence of liver metastasis (odds ratio [OR], 5.83; P &lt; 0.001 in Cohort A, OR, 2.84; P = 0.005 in Cohort B), absence of lymph node metastasis (OR, 2.18; P = 0.034 in Cohort A) and tissue RAS MT other than KRAS exon 2 (OR, 2.35; P = 0.049 in Cohort B) were significantly related to the emergence of Neo RAS WT. Among 6 Neo RAS WT patients tretd with EGFR inhibitors, one had partial response and another one had stable disease for at least 6 months. Conclusions: Liver and lymph node metastasis and RAS MT other than those in KRAS exon 2 are factors associated with the development of Neo RAS WT mCRC. EGFR inhibitors might be effective treatment.

Establishment of patient-derived tumor organoids to functionally inform treatment decisions in metastatic colorectal cancer

Metastatic colorectal cancer (mCRC) patients tend to have modest benefits from molecularly driven therapeutics. Patient-derived tumor organoids (PDTOs) represent an unmatched model to elucidate tumor resistance to therapy, due to their high capacity to resemble tumor characteristics. We used viable tumor tissue from two cohorts of patients with mCRC, naïve or refractory to treatment, respectively, for generating PDTOs. The derived models were subjected to a 6-day drug screening assay (DSA) with a comprehensive pipeline of chemotherapy and targeted drugs against almost all the actionable mCRC molecular drivers. For the second cohort DSA data were matched with those from PDTO genotyping. A total of 40 PDTOs included in the two cohorts were derived from mCRC primary tumors or metastases. The first cohort included 31 PDTOs derived from patients treated in front line. For this cohort, DSA results were matched with patient responses. Moreover, RAS/BRAF mutational status was matched with DSA cetuximab response. Ten out of 12 (83.3%) RAS wild-type PDTOs responded to cetuximab, while all the mutant PDTOs, 8 out of 8 (100%), were resistant. For the second cohort (chemorefractory patients), we used part of tumor tissue for genotyping. Four out of nine DSA/genotyping data resulted applicable in the clinic. Two RAS-mutant mCRC patients have been treated with FOLFOX-bevacizumab and mitomycin-capecitabine in third line, respectively, based on DSA results, obtaining disease control. One patient was treated with nivolumab-second mitochondrial-derived activator of caspases mimetic (phase I trial) due to high tumor mutational burden at genotyping, experiencing stable disease. In one case, the presence of BRCA2 mutation correlated with DSA sensitivity to olaparib; however, the patient could not receive the therapy. Using CRC as a model, we have designed and validated a clinically applicable methodology to potentially inform clinical decisions with functional data. Undoubtedly, further larger analyses are needed to improve methodology success rates and propose suitable treatment strategies for mCRC patients.

Genomic landscape and survival analysis of ctDNA "neo-RAS wild-type" patients with originally RAS mutant metastatic colorectal cancer.

The term "neo-RAS wild-type" refers to the switch to RAS wild-type disease in plasma circulating tumor DNA (ctDNA) from originally RAS mutant colorectal cancers. Consistently, the hypothesis to re-determine RAS mutational status in ctDNA at disease progression in RAS mutant mCRC opened to a new perspective for clinically-based selection of patients to be treated with EGFR inhibitors. Currently, the genomic landscape of "neo-RAS wild-type" is unknown. This is a prospective study aimed to investigate clinical and genomic features associated with RAS mutation clearance in a large cohort of RAS mutant mCRC patients who converted to RAS wild- type in liquid biopsy at failure of first-line treatments. Secondary aim was to investigate the long term prognostic significance of "true neo-RAS wild- type". 70 patients with stage IV RAS mutant colorectal cancer were prospectively enrolled. Plasma samples were collected at progression from first-line treatment. RAS/BRAF mutations in plasma were assessed by RT-PCR. In RAS/BRAF wild-type samples, ctDNA was used to generate libraries using a 17 genes panel whose alteration has clinical relevance. To investigate the prognostic significance of RAS mutation clearance, test curves for PFS and OS were represented by Kaplan-Meier estimator plot and Log-rank test. The most commonly detected actionable mutations in "neo-RAS wild-type" were: PIK3CA (35.7%); RET (11.9%); IDH1 (9.5%); KIT (7%); EGFR (7%); MET (4.7%); ERBB2 (4.7%); FGFR3 (4.7%). Both OS and post-progression survival were longer in patients with "neo-RAS wild-type" compared to those who remained RAS mutant (p<0.001 for both). De-novo-targetable mutations occured in a large percentage of "neo-RAS wild-type", being PIK3CA the most commonly detected. RAS mutation clearance in ctDNA is associated with long- term improvement of overall survival.

Regorafenib monotherapy as second-line treatment of patients with RAS-mutant advanced colorectal cancer (STREAM): an academic, multicenter, single-arm, two-stage, phase II study

Maintaining angiogenesis inhibition and switching the chemotherapy backbone represent the current second-line therapy in patients with RAS-mutant metastatic colorectal cancer (mCRC). Regorafenib, an oral multikinase inhibitor, prolonged overall survival (OS) in the chemorefractory setting. STREAM was an academic, multicenter, single-arm phase II trial, evaluating the activity of regorafenib in RAS-mutant mCRC, in terms of the rate of patients who were progression-free after 6 months from study entry (6mo-PF). Patients were pretreated with fluoropyrimidine, oxaliplatin, and bevacizumab. According to Simon's two-stage design, ≥18 patients 6mo-PF were needed in the overall population (N= 46). Secondary endpoints were safety, objective response rate (ORR), progression-free survival (PFS), and OS. Early metabolic response by [18F]2-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography ([18F]-FDG PET/CT) scan was an exploratory endpoint. EudraCT Number: 2015-001105-13. The number of patients 6mo-PF was 8/22 at the first stage and 14/46 in the overall population. The ORR was 10.9%, disease control rate was 54.6%, median (m)PFS was 3.6 months [95% confidence interval (CI) 1.9-6.7 months], mOS was 18.9 months (95% CI 10.3-35.3 months), and mPFS2 (from study entry to subsequent-line progression) was 13.3 months (95% CI 8.4-19.7 months). Long benefiter patients (>6mo-PF) significantly more often had a single metastatic site and lung-limited disease. No unexpected toxicity was reported. Grade ≥3 events occurred in 39.1% of patients, with hand-foot syndrome (13%), fatigue, and hyperbilirubinemia (6.5%) occurring mostly. Baseline metabolic assessment was associated with OS in the multivariate analysis, while early metabolic response was not associated with clinical outcomes. The study did not meet its primary endpoint. However, regorafenib was well tolerated and did not preclude subsequent treatments. Patients with good prognostic features (single metastatic site and lung-limited disease) reported clinical benefit with regorafenib. The exploratory metabolic analysis suggests that baseline [18F]-FDG PET/CT might be useful to select patients with a favorable outcome. A chemotherapy-free interval with regorafenib was associated with durable disease control in a selected group of patients with favorable clinical characteristics.

Multicentre single-arm phase II trial evaluating the safety and effiCacy of Panitumumab and iRinOtecan in NeoRAS Wild-type mEtaStatic colorectal cancer patientS (C-PROWESS trial): study protocol

IntroductionA new concept of ‘NeoRAS wild-type (WT)’, which means conversion of RAS status from RAS mutant to RAS WT after treatment, has been reported. Previous observational and proof-of-concept studies have...

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P20-2 Observational study to evaluate RAS status in ctDNA for mCRC patients with RAS mutant tumor: RASMEX study (JACCRO CC-17)

RAS status in tumor tissue is a predictive factor for the efficacy of anti-epidermal growth factor receptor (EGFR) antibodies (Abs) in patients (pts) with metastatic colorectal cancer (mCRC). Recently, several studies have shown that CRC tissue had heterogeneity of gene profiling, and the analysis of circulating tumor DNA (ctDNA) in blood samples could detect the change of gene alterations in tumors which were caused by chemotherapy. Bouchahda et al., demonstrated that nearly half of the pts with RAS mutant mCRC had no detectable RAS mutation (mut) in ctDNA after first-line chemotherapy.

P-68 Regorafenib monotherapy as second-line treatment of patients with RAS-mutant advanced colorectal cancer (STREAM): An academic, multicenter, single-arm, two-stage, phase 2 study

Therapeutic options after first-line treatment in patients with RAS mutant metastatic colorectal cancer (mCRC) are limited by poor clinical outcomes and lack of activity of anti-epidermal growth factor receptor drugs. Maintaining angiogenesis inhibition and switching the chemotherapy backbone represents the current therapeutic strategy of second-line mCRC therapy. Regorafenib, an oral broad-spectrum multikinase inhibitor targeting angiogenesis, has been shown to prolong overall survival (OS) and is approved after progression on chemotherapy. STREAM trial was an academic, multicentric, phase 2, single-arm, Simon’s two-stage design, aimed to establish the activity of regorafenib, defined as the rate of patients alive and progression free after 6months from study entry (6mo-PFS) in patients with RAS mutant mCRC, after progression on fluoropyrimidine, oxaliplatin and bevacizumab.Setting α and β errors at 0.10, defining a 6mo-PFS rate of 30% as p0 and 50% as p1, to consider the study positive ≧8 patients without progression at 6mo, were needed in the first stage (N=22) and ≧18 in the overall population (N=46). Regorafenib was administered orally at the approved schedule of 160mg day1-21 q28. Secondary endpoints were the evaluation of toxicity, objective response rate (ORR), progression-free survival (PFS), OS. Early metabolic response assessed by PET-CT scan after 2 weeks of treatment was an exploratory endpoint. Translational analyses are ongoing and will be presented at a later stage. Between November 2015, and December 2020, 46 patients were enrolled. median age was 67ys; 80.4% had ECOG performance status 0, 32.6% single organ involvement, 26% lung-limited disease. The study did not meet its predefined primary endpoint. Eight of the first 22 patients and 14 in the overall population were 6mo-PFS, as compared to the 18 required by the study protocol. At a median follow-up of 50.2 months (95%CI=24.2-56.3), ORR was 10.9%, Disease Control Rate (DCR) was 54.6%, median (m)PFS was 3.6mo (95%CI=1.9-6.7).Despite the short mPFS, regorafenib did not preclude a subsequent treatment: mPFS2 (from study entry to progression to subsequent treatment line) was 13.3mo (95%CI=8.4-19.7) and mOS was 18.9mo (95%CI=10.3-35.3). No unexpected toxicity was reported. Grade≥3 AEs occurred in 18 patients(39.1%), mostly hand foot syndrome(13%), fatigue and bilirubin increase(6.5%). Early metabolic response with PET/CT was not associated with ORR, mPFS and mOS. Baseline metabolic assessment, not predictive of ORR and mPFS, was significantly associated with mOS. A subgroup of patients, with single organ involvement, mostly lung-limited disease, low baseline PET-CT parameters, a low rate of early progression in first line (<6months=21.4%) and a long mPFS2 (23.3mo 95%CI=13.3-39.9), reported a long disease control with regorafenib: ORR=35.7%; mPFS=10.2mo (95%CI =8.6-13.5), mOS=38.8mo (95%CI=23.9-NR). Conversely, patients with higher radiological and metabolic burden of disease, higher rate of early progression in first-line (<6months=56.3%) and a shorter mPFS2 (8.4mo CI95%=6.1-13.3), reported unfavorable outcomes. Despite the study did not meet its primary endpoint, treatment with regorafenib had no unexpected toxicity and did not preclude efficacy of subsequent treatments. A subgroup of patients characterized by good prognostic features (limited disease, lung metastasis and low metabolic burden) had clinical benefit with regorafenib. Appropriate patients selection might guide the clinical development of regorafenib in an earlier setting, ensuring a chemotherapy-free interval in the treatment sequence.

Dynamic changes in RAS gene status in circulating tumour DNA: a phase II trial of first-line FOLFOXIRI plus bevacizumab for RAS-mutant metastatic colorectal cancer (JACCRO CC-11)

BackgroundFew prospective studies have used liquid biopsy testing in RAS-mutant metastatic colorectal cancer (mCRC), and its clinical significance remains unknown. Therefore, this study aimed to carry out a biomarker analysis by liquid biopsy using updated data of the phase II trial of FOLFOXIRI plus bevacizumab as first-line chemotherapy for RAS-mutant mCRC.Materials and methodsA total of 64 patients who received modified FOLFOXIRI regimen (irinotecan 150 mg/m2, oxaliplatin 85 mg/m2, levofolinate 200 mg/m2, and fluorouracil 2400 mg/m2) plus bevacizumab biweekly were enrolled. The primary endpoint was the objective response rate (ORR). Plasma samples were collected at pre-treatment, 8 weeks after treatment, and progression in participants included in the biomarker study. The levels of circulating tumour DNA (ctDNA) and specific KRAS and NRAS variants were evaluated using real-time PCR assays.ResultsThere were 62 patients (median age: 62.5 years, 92% performance status 0, 27% right side) who were assessable for efficacy and 51 for biomarker analysis. ORR was 75.8% (95% confidence interval 65.1% to 86.5%). The median progression-free survival was 12.1 months, and the median overall survival (OS) was 30.2 months. In 78% of patients, RAS mutations disappeared in the ctDNA at 8 weeks after treatment; these patients tended to have better outcomes than those with RAS mutations. Interestingly, RAS mutations remained undetectable during progression in 62% of patients. Survival analysis indicated that the median OS from progression was significantly longer in patients with RAS mutation clearance than in those with RAS mutation in the ctDNA at disease progression (15.1 versus 7.3 months, hazard ratio: 0.21, P = 0.0046).ConclusionsOur biomarker study demonstrated no RAS mutations in ctDNA at disease progression in 62% of patients with RAS-mutant mCRC. Both OS and post-progression survival were better in patients with clearance of RAS mutations in ctDNA after triplet-based chemotherapy.

Efficacy and safety analysis of bevacizumab combined with capecitabine in the maintenance treatment of RAS-mutant metastatic colorectal cancer.

What is known and objectivesThe optimal strategy for maintenance therapy in patients with metastatic colorectal cancer (mCRC) remains controversial. Considering that, beyond progression, co‐therapy with bevacizumab and cytotoxic chemotherapy showed less toxicity and a significant disease control rate. We aimed to investigate the differences in efficacy and safety between bevacizumab combined with capecitabine maintenance therapy and capecitabine monotherapy for RAS‐mutant mCRC （as defined by mutations in KRAS and NRAS exons 2–4）controlled by bevacizumab plus FOLFIRI chemotherapy for at least 12 weeks.MethodsWe retrospectively analysed patients with RAS‐mutant mCRC admitted to the Department of Oncology, Huizhou Municipal Central Hospital from December, 2015 to December, 2020. All patients were first treated with bevacizumab combined with FOLFIRI for at least 12 weeks of induction therapy. 154 patients whose disease was brought under control then continued maintenance therapy. 78 patients were in the observation group (bevacizumab plus capecitabine) and 76 patients were in the control group (capecitabine alone). The efficacy and adverse effects of maintenance treatment were compared between the two groups. The clinicopathological characteristics such as sex, age, performance status (PS) score, primary tumour site, degree of pathological differentiation, baseline carcinoembryonic antigen (CEA) level, microsatellite instability (MSI) status, number of metastatic tumour sites and efficacy of induction treatment were compared in terms of prognosis.Results and discussionThe median progression‐free survival (mPFS)of patients was 9.0 months (95% CI 8.0–10.0) in the observation group and 7.2 months (95% CI 6.0–8.4) in the control group, with a statistically significant difference (p < 0.05). The baseline CEA level was an independent prognostic factor. Both groups tolerated the toxic side effects.What is new and conclusionBevacizumab combined with capecitabine was well tolerated and contributed to a longer PFS time than capecitabine alone, and it is worthy of popularization in clinical practice.

RAS Mutation Conversion in Bevacizumab-Treated Metastatic Colorectal Cancer Patients: A Liquid Biopsy Based Study.

Simple SummaryRecent evidence has been provided that the clonal evolution of mutant RAS colorectal tumors may lead to the negative selection of mutant RAS clones, with the appearance of a time window characterized by the disappearance of RAS mutant clones in plasma. We demonstrate here for the first time that the use of bevacizumab in the first-line treatment is the most significant factor for RAS conversion from mutant to wild type in plasma. The frequent appearance of this “RAS wild-type * window” in patients treated with a first line treatment containing bevacizumab could possibly present them as candidates for second line treatment with anti-EGFR monoclonal antibodies, which are otherwise precluded.Liquid biopsies have shown that, in RAS mutant colorectal cancer, the conversion to RAS wild-type * status during the course of the disease is a frequent event, supporting the concept that the evolutionary landscape of colorectal cancer can lead to an unexpected negative selection of RAS mutant clones. The aim of the present study was to clarify whether the negative selection of RAS mutation in plasma might be drug-dependent. For this purpose, we used liquid biopsy to compare the rate of conversion from RAS mutant to RAS wild-type * in two groups of originally RAS mutant mCRC patients: the first treated with chemotherapy alone, while the second was treated with chemotherapy combined with bevacizumab. Serial liquid biopsies were performed at 3 months (T1), 6 months (T2), 9 months (T3), and 12 months (T4) after starting first line treatments. We found that the only independent variable significantly associated to RAS status conversion was the use of bevacizumab. RAS conversion was not found associated to tumor burden reduction, although bevacizumab-treated patients who converted to RAS wild-type * had a significantly longer PFS compared to patients who remained RAS mutant. The appearance of a “RAS wild-type * window”, mainly in bevacizumab-treated patients, might present them as candidates for second line treatment with anti-EGFR, which was otherwise precluded.

An observational study to evaluate RAS mutations in circulating tumor DNA after standard chemotherapies for metastatic colorectal cancer patients with tumors harboring RAS mutation: RASMEX study (JACCRO CC-17).

TPS230 Background: RAS status in tumor tissue is a predictive factor for the efficacy of anti-epidermal growth factor receptor (EGFR) antibodies therapy in patients (pts) with metastatic colorectal cancer (mCRC). In mCRC pts with tumors harboring RAS mutation, anti-EGFR antibodies therapy has the lack of clinical benefit; thus, the survival of RAS mutant mCRC pts is shorter compared to RAS wild mCRC pts. Recently, several studies have shown that colorectal cancer tissue had heterogeneity of gene profiling, and the analysis of circulating tumor DNA (ctDNA) in blood samples could detect the change of gene alterations in tumors which were caused by chemotherapy. Bouchahda et al., demonstrated that nearly half of the pts with RAS mutant mCRC had no detectable RAS mutation in ctDNA after first-line chemotherapy; moreover, some of the pts had clinical benefits from post-anti-EGFR antibodies therapy. Therefore, anti-EGFR antibodies therapy might become a novel treatment option for RAS mutant mCRC pts without RAS mutations in ctDNA after chemotherapies. Other report also showed the frequency of no RAS mutations in ctDNA was about 1%. There have been few studies to prospectively evaluate the RAS status in ctDNA for mCRC pts with RAS mutant tumors treated with standard chemotherapies. We, therefore, conducted an observational study to evaluate RAS mutations and the mutation allele frequency in ctDNA for mCRC pts with RAS mutant tumors who were treated with first- or second-line chemotherapy. Methods: This study is a multi-center observational/translational study in 67 facilities. The key eligibility criteria are as follows: 1) Eastern Cooperative Oncology Group Performance status 0-1, 2) histologically proven unresectable mCRC, 3) RAS mutation in tumor tissue, 4) refractory or intolerable after response to prior fluoropyrimidine-containing regimen. OncoBEAM RAS CRC kit is used to investigate RAS status in ctDNA just after first- or second-line treatment in enrolled pts. The primary endpoint is the frequency of pts without RAS mutations in ctDNA. Secondary endpoints include mutation allele frequency of RAS in ctDNA and clinical outcomes of pre- and post-treatments (overall response rate, disease control rate, overall survival, and progression-free survival). As the exploratory analysis, gene alterations related to the resistant mechanism of anti-EGFR antibodies (BRAF, PIK3CA, ERBB2, MET) are analyzed in pts without RAS mutations in ctDNA. We assume that no RAS mutations are observed in ctDNA in at least 1 % pts. We expect that one patient with no RAS mutations in ctDNA is detected in 100 pts; thus, the sample size of 300 pts is set for our study. Accrual is starting in April 2021. Clinical trial information: UMIN000043442.

Trastuzumab deruxtecan in patients with HER2-overexpressing locally advanced, unresectable, or metastatic colorectal cancer (mCRC): A randomized, multicenter, phase 2 study (DESTINY-CRC02).

TPS224 Background: Trastuzumab deruxtecan (T-DXd) is an antibody-drug conjugate comprising an anti-HER2 antibody (trastuzumab) linked to a potent topoisomerase I inhibitor (DXd). T-DXd has been approved to treat HER2-positive metastatic breast cancer (United States [US], Japan, Europe, Israel) and advanced gastric cancer (US, Japan, Israel). It is currently being evaluated in other solid tumor types including colorectal cancer. The phase 2 DESTINY-CRC01 study included patients with RAS wild-type mCRC, with a median 4 (range, 2-11) prior lines of therapy. Preliminary results in patients with HER2-overexpressing (IHC 3+ or IHC 2+/ISH+) mCRC showed T-DXd treatment (6.4-mg/kg intravenously [IV] every 3 weeks [Q3W]) resulted in a confirmed objective response rate (ORR) of 45.3% (24/53; 95% CI, 31.6-59.6%) and a median progression-free survival (PFS) of 6.9 months (95% CI, 4.1-not estimable; Siena J Clin Oncol. 2020). Activity was also seen in patients treated with prior anti-HER2 therapy. Although 5.4-mg/kg and 6.4-mg/kg doses of T-DXd have shown clinical efficacy in multiple cancer indications, the lower dose has not yet been tested in patients with HER2-overexpressing mCRC. Preliminary data also suggest T-DXd may be active in RAS mutant mCRC, unlike other anti-HER2 therapies. The DESTINY-CRC02 study aims to determine efficacy and safety of T-DXd in patients with HER2-overexpressing, RAS wild-type or mutant mCRC at 5.4-mg/kg and 6.4-mg/kg doses. Methods: DESTINY-CRC02 (NCT04744831) is a multicenter, randomized, double-blind, 2-arm, parallel phase 2 study that will be conducted in 2 stages. Eligible patients (≥18 years; ≥20 years in Japan, Taiwan, and Korea) will have HER2-overexpressing (IHC 3+ or IHC 2+/ISH+) locally advanced, unresectable or metastatic CRC and have previously received chemotherapy, anti-EGFR therapy, anti-VEGF treatment, and/or anti–PD-1/PD-L1 therapy, as clinically indicated. Prior anti-HER2 therapy will be allowed. In stage 1, patients will be randomly assigned 1:1 to receive T-DXd IV Q3W at a dose of 5.4-mg/kg (n = 40; arm 1) or 6.4-mg/kg (n = 40; arm 2). Randomization will be stratified by ECOG PS (0 or 1), HER2 status (IHC 3+ or IHC 2+/ISH+), and RAS status (wild-type or mutant). After stage 1 enrollment is complete, eligible patients in stage 2 (n = 40) will receive T-DXd 5.4 mg/kg until disease progression or other treatment discontinuation criteria are met. The study is actively enrolling and aims to enroll 120 patients across 60 sites. The primary objective is to assess efficacy of T-DXd at the 5.4-mg/kg and 6.4-mg/kg doses, with a primary endpoint of confirmed ORR by blinded independent central review. Secondary endpoints include investigator-assessed ORR, PFS, duration of response, disease control rate, clinical benefit rate, overall survival, pharmacokinetics, and safety. Clinical trial information: NCT04744831.

The role of genetic variants involved with ferroptosis regulator genes in predicting outcomes in patients (pts) with RAS-mutant metastatic colorectal cancer (mCRC): Data from MAVERICC and TRIBE trials.

197 Background: Ferroptosis, an iron-dependent programmed cell death, is one of the anti-tumor mechanisms of anti-angiogenesis drugs. RAS mutation can confer ferroptosis in colorectal cancer (CRC). Previous studies suggested that polymorphisms of ferroptosis regulator genes are associated with the increased risk of CRC. Therefore, we hypothesized that genetic variants in the ferroptosis regulator genes may predict first-line treatment outcome in RAS-mutant mCRC pts treated with bevacizumab (bev)-based chemotherapy. Methods: Genomic DNA from blood samples of mCRC pts enrolled in two independent randomized trials, MAVERICC (FOLFIRI+bev arm: discovery cohort, RAS-mutant, n = 56; control-1: RAS-wildtype, n = 87) and TRIBE (FOLFOXIRI+bev arm: validation cohort, RAS-mutant, n = 57; control-2: RAS-wildtype, n = 34), was genotyped through the OncoArray, a customized array manufactured by Illumina including approximately 530K SNP markers. The impact on outcome of 13 selected SNPs in 5 main ferroptosis regulator genes (ACSL4, LPCAT3, SLC3A2, SLC7A11, ALOX15) was analyzed. Results: In the MAVERICC bev cohort, pts with RAS-mutant tumors carrying ALOX15 rs7217186 any C allele (n = 35) showed significant longer overall survival (OS) than carrier of T/T allele (n = 5) in both univariate (24.97 vs. 12.22 months, hazard ratio [HR] = 0.23; 95% confidence interval [CI]: 0.06-0.9; p = 0.02) and multivariate (HR = 0.06; 95%CI 0.007-0.5; p = 0.009) analysis. In the TRIBE bev cohort, RAS-mutant carriers of any C allele (n = 30) showed numerically longer progression-free survival (PFS), compared to carriers of T/T allele (n = 13) in both univariate (11.91 vs. 9.47 months, HR = 0.45; 95%CI 0.2-1.02; p = 0.05) and multivariate (HR = 0.42; 95%CI 0.16-1.1; p = 0.09) analysis. Conversely, RAS-wildtype carriers of any C allele (n = 17) showed significant shorter PFS than T/T carriers in the TRIBE bev cohort (8.91 vs. 15.59 months, univariate HR = 3.39, 95%CI: 1.03-11.18, p = 0.04). Conclusions: Our study demonstrated for the first time that ALOX15 polymorphisms may have different predictive values for the bev-based treatment in mCRC patients based on RAS mutational status. These findings may provide novel insights for the combination of ferroptosis inducers and anti-VEGF treatment.

The temporal evaluation of RAS and BRAF mutation by liquid biopsy at progression after bevacizumab combinations in patients with metastatic colorectal cancer (mCRC).

e15587 Background: Expanded RAS analysis is essential for the selection of biologic agents in mCRC. RAS mutations indicates anti-EGFR unresponsiveness. In this study, we aimed to investigate RAS and BRAF mutations by liquid biopsy at progression in patients with RAS mutant mCRC. Methods: Sixty patients with mCRC who harbored tissue RAS mutations were prospectively analyzed between July 2019 and April 2020. All the patients treated with chemotherapy plus bevacizumab combinations . The plasma samples of the patients were analyzed after progression of bevacizumab combinations. RAS mutation profile was evaluated in plasma using Idylla PCR-based molecular diagnostics method, which enables rapid detection of common mutations in RAS and BRAF genes in circulating tumor DNA (ctDNA). Kaplan-Meier method was used for survival analysis and log-rank test was performed for comparison of groups. Results: The median age of the patients was 60 years (IQR:35-83 years) and female was (n=23, 38.3%). Primary tumor was located in the left colon in 81.7% of all patients. There were 95.0% KRAS and 5% NRAS mutations in baseline tissue biopsy. As a result of liquid biopsy after progression, 55.0% of the patients had KRAS, 3.3% NRAS and 3.3% had BRAF mutations. The RAS mutation detected in 58.3% of the patients. While there was no significant difference in terms of clinicopathological features between wild type (RAS/BRAF) and mutant type (RAS/BRAF) determined by liquid biopsy, the overall survival (OS) of the wild type group was significantly longer than mutant group (43.8 vs. 20.4 months, p= 0.002). Conclusions: This study demonstrated that there may be changes in RAS/BRAF mutation from plasma analysis after progression in patients with mCRC. Since better survival in the patient group with wild type was detected compared to the RAS concordance group, the evaluation of RAS mutation status at the time of progression may be important in terms of disease prognosis and treatment options.

Trastuzumab deruxtecan in patients with HER2-overexpressing locally advanced, unresectable, or metastatic colorectal cancer (mCRC): A randomized, multicenter, phase 2 study (DESTINY-CRC02).

TPS3620 Background: Trastuzumab deruxtecan (T-DXd) is an antibody–drug conjugate consisting of an anti-HER2 antibody (trastuzumab) linked to a potent topoisomerase I inhibitor (DXd). T-DXd has been approved to treat HER2-positive metastatic breast cancer (United States, Japan, Europe) and advanced gastric cancer (United States, Japan). It is currently being evaluated in other solid tumor types including colorectal cancer. The phase 2 DESTINY-CRC01 study included patients with RAS wild-type mCRC, with median 4 (range, 2-11) prior lines of therapy. Preliminary results in patients with HER2-overexpressing (IHC 3+ or IHC 2+/ISH+) mCRC showed T-DXd treatment (6.4 mg/kg intravenously [IV] every 3 weeks [Q3W]) resulted in a confirmed objective response rate (ORR) of 45.3% (24/53; 95% CI, 31.6%-59.6%) and a median progression-free survival (PFS) of 6.9 months (95% CI, 4.1 months-not evaluable; Siena J Clin Oncol. 2020;38[15]:4000). Activity was also seen in patients treated with prior anti-HER2 therapy. Although 5.4-mg/kg and 6.4-mg/kg doses of T-DXd have shown clinical efficacy in multiple cancer indications, the lower dose has not yet been tested in patients with HER2-overexpressing mCRC. Preliminary data also suggest T-DXd may be active in RAS mutant mCRC, unlike other anti-HER2 therapies. The DESTINY-CRC02 study aims to determine efficacy and safety of T-DXd in patients with HER2-overexpressing, RAS wild-type or mutant mCRC at 5.4-mg/kg and 6.4-mg/kg doses. Methods: DESTINY-CRC02 (NCT04744831) is a multicenter, randomized, double-blind, 2-arm, parallel phase 2 study that will be conducted in 2 stages. Eligible patients (≥18 years; ≥20 years in Japan, Taiwan, and Korea) will have HER2-overexpressing (IHC 3+ or IHC 2+/ISH+) locally advanced, unresectable or metastatic CRC and have previously received chemotherapy, anti-EGFR therapy, anti-VEGF treatment, and/or anti–PD-1/PD-L1 therapy, as clinically indicated. Prior anti-HER2 therapy will be allowed. In stage 1, patients will be randomly assigned 1:1 to receive T-DXd IV Q3W at a dose of 5.4 mg/kg (n = 40; arm 1) or 6.4 mg/kg (n = 40; arm 2). Randomization will be stratified by ECOG PS (0 or 1), HER2 status (IHC 3+ or IHC 2+/ISH+), and RAS status (wild-type or mutant). After stage 1 enrollment is complete, eligible patients in stage 2 (n = 40) will receive T-DXd 5.4 mg/kg until disease progression or other treatment discontinuation criteria are met. The study is actively enrolling and aims to enroll 120 patients across 60 sites. The primary objective is to assess efficacy of T-DXd at the 5.4-mg/kg and 6.4-mg/kg doses, with a primary end point of confirmed ORR by blinded independent central review. Secondary end points include investigator-assessed ORR, PFS, duration of response, disease control rate, clinical benefit rate, overall survival, pharmacokinetics, and safety. Clinical trial information: NCT04744831.

Circulating Methylated DNA to Monitor the Dynamics of RAS Mutation Clearance in Plasma from Metastatic Colorectal Cancer Patients.

Simple SummaryOngoing clinical trials are recently investigating the efficacy of second-line EGFR inhibitors in initially RAS mutant metastatic colorectal cancer patients who convert to RAS wild-type in plasma, as assessed by circulating tumor DNA (ctDNA) analysis. To this purpose, discriminating between patients with a real clearance of RAS mutations in plasma (real wild-type) from those who do not shed ctDNA is mandatory. The aim of the present study was to confirm the presence of ctDNA in patients with RAS mutation clearance in plasma at different time points, using a colon-cancer-specific five-gene methylation panel. The methylation test confirmed the presence of ctDNA in most RAS wild-type samples at the time of disease progression, thus confirming that the negative selection of RAS mutant clones during the clonal evolution of mutant RAS colorectal cancer is not an infrequent event.The clearance of RAS mutations in plasma circulating tumor DNA (ctDNA) from originally RAS-mutant metastatic colorectal cancer (mCRC) has been recently demonstrated. Clinical trials investigating whether RAS mutant mCRC who “convert” to wild-type in plasma might benefit from EGFR blockade are ongoing. Detection of tumor-specific DNA methylation alterations in ctDNA has been suggested as a specific tool to confirm the tumoral origin of cell-free DNA. We monitored RAS clearance in plasma from patients with RAS-mutant mCRC at baseline (pre-treatment) (T0); after 4 months of first-line therapy (T1); at the time of first (T2) and second (T3) progression. A five-gene methylation panel was used to confirm the presence of ctDNA in samples in which RAS mutation clearance was detected. At T1, ctDNA analysis revealed wild-type RAS status in 83% of samples, all not methylated, suggesting at this time point the lack of ctDNA shedding. At T2, ctDNA analysis revealed wild-type RAS status in 83% of samples, of which 62.5% were found methylated. At T3, 50% of wild-type RAS samples were found methylated. Non-methylated samples were found in patients with lung or brain metastases. This five-gene methylation test might be useful to confirm the presence of ctDNA in RAS wild-type plasma samples.