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.

Encorafenib and cetuximab versus irinotecan/cetuximab or FOLFIRI/cetuximab in Chinese patients with BRAF V600E mutant metastatic colorectal cancer: The NAUTICAL CRC study.

LBA3559 Background: BRAF V600E mutations are present in 8-12% worldwide of patients with metastatic colorectal cancer (mCRC) and linked with a poor prognosis. Encorafenib + cetuximab (E+C) was approved by the FDA and EMA for patients with BRAF V600E-mutant mCRC who received prior systemic therapy, based on data from the BEACON CRC study. Methods: This Phase II, multicenter, randomized, open-label, 2-arm study evaluated E+C vs irinotecan + cetuximab or FOLFIRI + cetuximab (control arm) in Chinese patients with BRAF V600E mutant mCRC whose disease progressed after 1 or 2 prior treatment lines in the metastatic setting. A safety lead-in initially conducted in 10 patients reported no DLTs. Eligible patients had mCRC and a BRAF V600E mutation in tumor tissue determined by a local assay before screening and centrally confirmed. Patients were randomly assigned to the doublet arm (E+C) or the control arm in a 2:1 ratio, respectively. Randomization was stratified by baseline ECOG performance status (0 vs 1) and prior use of irinotecan (yes vs no). The primary objective of the randomized phase was to compare the efficacy of E+C vs the control arm, as measured by PFS (assessed by blinded independent central review). Secondary objectives included PFS assessed by the investigator, ORR, DOR, DCR, TTR, OS, QoL, and safety and tolerability of E+C. Results of the randomized phase of the study are reported. Results: At data cut-off (19 Dec 2023), 65 patients were enrolled in the E+C arm and 32 in the control arm. Median patient age was 56 years, the primary cancer site was the left colon in 56.7% of patients, 48.5% had metastases to ≥3 organs, 56.7% had liver metastases, 77.3% received one prior metastatic treatment, and 22.7% received 2 prior metastatic treatments. Results are shown below for E+C vs the control arm, respectively. Median PFS assessed by BICR was 4.2 mo vs 2.5 mo (HR 0.37; 95% CI: 0.20, 0.68; P=0.0004). Median OS was 11.6 mo vs 8.2 mo (HR for death 0.55; 95% CI: 0.31, 0.99). Confirmed ORR was 24.6% (95% CI: 14.8, 36.9) vs 6.3% (95% CI: 0.8, 20.8). Treatment emergent adverse events (TEAEs) of grade 3 or higher occurred in 47.7% vs 51.9% of patients. Treatment-related grade 3 or higher occurred in 24.6% and 44.4% of patients. The most frequent TEAEs were anemia (30.8% vs 37%), vomiting (26.2% vs 33.3%), rash (24.6% vs 29.6%), weight loss (23.1% vs 18.5%), hypoalbuminemia (21.5% vs 22.2%), and melanocytic naevus (21.5% vs 0%). Three patient deaths were reported during treatment: unknown cause (n=1) and pneumonia (n=1) in the E+C arm and septic shock (n=1) in the control arm. Conclusions: Treatment with a combination of encorafenib and cetuximab is effective and well tolerated in Chinese patients with BRAF V600E mutant mCRC, resulting in a significantly longer PFS than standard therapies. These results are consistent with those previously reported in the BEACON study. Clinical trial information: NCT05004350 .

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.

Monitoring ctDNA RAS Mutational Status in Metastatic Colorectal Cancer: A Trial Protocol of RAS-trace and RAS-trace-2 Studies.

Spatial and temporal heterogeneities of RAS and other molecular genes should be considered in the treatment of metastatic colorectal cancer (mCRC) treated with anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (mAbs); acquired RAS mutation is sometimes observed at disease progression of treatment with the anti-EGFR mAb. At the same time, discrepancy of RAS status from tissues and circulating tumor DNA (ctDNA) in the same patient is sometimes observed. Based on this, we commenced two observational studies to clarify these heterogeneities of RAS and BRAF in mCRC, using next generation sequencing from liquid biopsy. RAS-trace study is an observational study to monitor ctDNA RAS/BRAF/PIK3CA status every 4-12 weeks using the Plasma-SeqSensei™ CRC RUO Kit (Sysmex Inostics GmbH) in mCRC with RAS/BRAF wild-type (wt) on tumor tissue. The primary endpoint was the time to the acquired RAS mutations. A total of 42 patients has been accrued. RAS-trace-2 study is also an observational study aimed at comparing the efficacy of the anti-EGFR mAb in ctDNA RAS/BRAF wt with ctDNA RAS or BRAF mutant mCRC patients, whose RAS/BRAF are wt in tumor tissue. The primary endpoint was progression-free survival in patients with ctDNA RAS/BRAF wt and RAS or BRAF mutant. A total of 240 patients will be accrued over 2 years. These trials will help us understanding the clinical significance of spatial and temporal heterogeneities of RAS, BRAF and other genes, while optimizing the anti-EGFR mAb treatment strategies in mCRC.

Abstract 5847: Characterizing mechanisms of BRAF/MEK inhibitor resistance in BRAF V600 mutant colorectal cancer vs. melanoma

Abstract Background: BRAF V600 mutations comprise ~80% of all oncogenic BRAF mutations in metastatic colorectal cancer (mCRC). While most cancers with BRAF V600 mutations can be effectively treated with combined BRAF and MEK inhibition, BRAF V600 mutant mCRC acquire resistance through EGFR-mediated signaling. The profound difference in response rates to BRAF/MEK inhibitors in BRAF V600 mutant mCRC (12%) vs. melanoma (63-68%) is not sufficiently explained by increased EGFR signaling in CRC. Therefore, we sought to characterize the differences that exist between BRAF V600 mutant CRC and melanomas that could explain the differential sensitivity to BRAF/MEK inhibition and identify more effective treatments for BRAF V600 mutant CRC. Methods: We assessed cell survival by clonogenic assay in the presence of small molecule inhibitors. In parallel, we mined TCGA RNAseq data to calculate the MAPK Pathway Activity Score (MPAS). RTK expression was assessed in TCGA data from patients with BRAF V600 mutant CRC vs. melanoma. We developed cells with acquired resistance to BRAF+MEK inhibitors (Encorafenib+Binimetinib; E+B) by culturing cells in increasing concentrations of drug over several months. RNA-sequencing and analysis was performed on parental and resistant cells treated with vehicle control or BRAF+MEK inhibitors. Results: When comparing the efficacy of BRAF+MEK inhibitors across BRAF V600 mutant cells, we found that BRAF V600 mutant CRC cell lines (n=2) were less sensitive than melanoma cell lines (n=2). MPAS scores were significantly lower in BRAF V600 mutant CRC (n=46) vs. melanoma (n=188) tumors. We interrogated protein array data from the DepMap and identified increased activation of several RTKs (EGFR, HER2, HER3) in BRAF V600 CRC (n=8) vs. melanoma (n=39) cell lines. Similarly, we established resistant HT29 (BRAF V600 CRC) cells and observed sustained MAPK pathway activity despite a lack of difference in EGFR activity in the presence of BRAF+MEK inhibitor treatment. Both HT29 parental and resistant cells showed re-establishment of MAPK signaling after 72 hours. Resistant SkMel28 (BRAF V600 melanoma) cells showed increased pERK levels compared to resistant HT29 cells. RNAseq revealed increased expression of multiple RTKs (PDGFRB, ERBB2, ERBB3) and ligands/growth factors for multiple RTKs (FGF3, PDGFA, HB-EGF) in resistant HT29 cells. Shp2 is a protein tyrosine phosphatase that regulates signaling of multiple RTKs to activate the MAPK pathway. Accordingly, we assessed the efficacy of an inhibitor of Shp2 (TNO155) overcoming MAPKi resistance in BRAF V600 CRC cells. We confirmed that E+B+TNO155 more effectively inhibited cell growth and MAPK pathway activity in BRAF V600 CRC cell lines (n=2) in vitro. Conclusion: Together, these data identify key, actionable drivers of MAPK inhibitor resistance in CRC and highlight Shp2 as a potential therapeutic target for BRAF V600 CRC. Citation Format: Jennifer Maxwell, Emmanuelle Rousselle, Lucy An, April Rose. Characterizing mechanisms of BRAF/MEK inhibitor resistance in BRAF V600 mutant colorectal cancer vs. melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5847.

The relationship between clinical and pathological findings and FDG - PET uptake in metastatic colorectal cancers.

In metastatic colorectal cancer (mCRC), the genetic structure and cell metabolism of the primary tumor lesion might be different from metastatic lesions. It is thought that cell-level glucose metabolism may differ due to the difference in RAS wild and mutant mCRC patients' prognosis. In this study, we aimed to compare 2-deoxy-2-[fluorine-18]-fluoro-D-glucose Positron Emission Tomography (18F-FDG PET/CT) uptake levels for KRAS mutation status and primary-metastatic tumor localization. Our study is a retrospective cohort analysis that included RAS mutation status study and staging-oriented 18F-FDG PET/CT conducted on mCRC patients. There was no significant relationship between metastasis and primary tumor maximum Standardized uptake value (SUVmax) values according to the KRAS mutational status (P > 0.05). Patients with liver metastasis along with mutant BRAF mutation status had significantly higher SUVmax values in PET-CT scans (P = 0.04). There was a negative correlation between SUVmax values of lung metastases and overall survival (r = -0.35, P = 0.04). Patients with high carcinoembryonic antigen (CEA) levels had significantly higher SUVmax values of lung metastasis than patients with normal CEA levels (P = 0.009). Patients with high CA19-9 levels had significantly higher SUVmax values of liver, peritoneal, and bone metastasis than patients with normal CA19-9 levels (P = 0.002, P = 0.001, P = 0.004, respectively). There was no significant correlation between SUVmax values of metastasis and Lactate dehydrogenase (LDH) values. Liver metastasis of right-sided mCRCs had significantly higher SUVmax values (P = 0.03). We could not demonstrate a significant association between KRAS mutation and SUVmax values of PET scan in primary or metastatic tumor sites in advanced CRC.

Fluoropyrimidine type, patient age, tumour sidedness and mutation status as determinants of benefit in patients with metastatic colorectal cancer treated with EGFR monoclonal antibodies: individual patient data pooled analysis of randomised trials from the ARCAD database

BackgroundKRAS mutations in metastatic colorectal cancer (mCRC) are used as predictive biomarkers to select therapy with EGFR monoclonal antibodies (mAbs). Other factors may be significant determinants of benefit.MethodsIndividual patient data from randomised trials with a head-to-head comparison between EGFR mAb versus no EGFR mAb (chemotherapy alone or best supportive care) in mCRC, across all lines of therapy, were pooled. Overall survival (OS) and progression-free survival (PFS) were compared between groups. Treatment effects within the predefined KRAS biomarker subsets were estimated by adjusted hazard ratio (HRadj) and 95% confidence interval (CI). EGFR mAb efficacy was measured within the KRAS wild-type subgroup according to BRAF and NRAS mutation status. In both KRAS wild-type and mutant subgroups, additional factors that could impact EGFR mAb efficacy were explored including the type of chemotherapy, line of therapy, age, sex, tumour sidedness and site of metastasis.Results5675 patients from 8 studies were included, all with known mCRC KRAS mutation status. OS (HRadj 0.90, 95% CI 0.84–0.98, p = 0.01) and PFS benefit (HRadj 0.73, 95% CI 0.68–0.79, p < 0.001) from EGFR mAbs was observed in the KRAS wild-type group. PFS benefit was seen in patients treated with fluorouracil (HRadj 0.75, 95% CI 0.68–0.82) but not with capecitabine-containing regimens (HRadj 1.04, 95% CI 0.86–1.26) (pinteraction = 0.002). Sidedness also interacted with EGFR mAb efficacy, with survival benefit restricted to left-sided disease (pinteraction = 0.038). PFS benefits differed according to age, with benefits greater in those under 70 (pinteraction = 0.001). The survival benefit was not demonstrated in those patients with mutations found in the KRAS, NRAS or BRAF genes. The presence of liver metastases interacted with EGFR mAb efficacy in patients with KRAS mutant mCRC (pinteraction = 0.004).ConclusionThe benefit provided by EGFR mAbs in KRAS WT mCRC is associated with left-sided primary tumour location, younger patient age and absence of NRAS or BRAF mutations. Survival benefit is observed with fluorouracil but not capecitabine. Exploratory results support further research in KRAS mutant mCRC without liver metastases.

Impact of early tumor shrinkage and depth of response in patients with BRAF V600E-mutant metastatic colorectal cancer.

142 Background: Early tumor shrinkage (ETS) and the depth of response (DpR) are early on-treatment surrogate markers for survival in patients with metastatic colorectal cancer (mCRC) receiving anti-epidermal growth factor receptor (EGFR) monoclonal antibody. However, the utility of ETS and DpR for BRAF V600E mutant (MT) mCRC which has a poor prognosis remains unclear. The aim of this study is to evaluate the association between ETS and DpR and clinical outcomes in BRAF V600E MT mCRC. Methods: mCRC patients who were diagnosed BRAF V600E MT and treated with 1st line chemotherapy from June 2011 to March 2023 at single cancer institute were enrolled. We analyzed the association between ETS and DpR and clinical outcome in patients who had at least one target lesion. Subgroup analysis of clinical factors related to progression free survival (PFS) and overall survival (OS) was performed using multivariate analysis. ETS was defined as the relative change in the sum of the longest diameters of RECIST target lesions at first follow-up CT scan compared to baseline and DpR was defined as the relative change in the sum of the longest diameters of RECIST target lesions at the nadir in the absence of new lesions or progression of non-target lesions compared to baseline. Results: In total, 54 patients of BRAF V600E MT mCRC had at least one target lesion. In total of StageI-IV CRC patients, the incidence of BRAF V600E MT was 6.3% (233/3705). Patients with ETS ≥ 20% and DpR ≥ 25% (median value) were 24 (44.4%) and 27 (50%) respectively. PFS was 7.5 months (95% confidence interval (CI), 5.0-9.9) and OS was 17.1 months (95% CI, 11.7-20.2). Patients with ETS ≥ 20% had longer PFS and tended to have longer OS than those with non-ETS, with a median PFS of 9.8 months vs. 4.8 months (P Log-rank = 0.048, hazard ratio (HR), 0.55; 95% CI, 0.30-1.00), and a median OS of 22.6 months vs. 11.6 months (P Log-rank = 0.18, HR, 0.67; 95% CI, 0.37-1.21). Patients with DpR ≥ 25% had also longer PFS and OS than those with non-DpR, with a median PFS of 11.0 vs. 4.3 months (P Log-rank &lt; 0.01, HR, 0.36; 95% CI, 0.20-0.66) and a median OS of 22.6 vs. 10.1 months (P Log-rank = 0.047, HR, 0.55; 95% CI, 0.31-1.00). Median time to DpR was 3.05 months. In multivariate analysis, DpR was significantly associated with both longer PFS (HR: 0.27, 95% CI: 0.14–0.55, P &lt; 0.01) and OS (HR: 0.52, 95% CI: 0.29–0.96, P = 0.04). Conclusions: ETS and DpR may be early surrogate markers for clinical outcome in BRAF V600E MT mCRC who were treated with 1st line chemotherapy.

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.

STELLAR-303: A phase 3 study of XL092 in combination with atezolizumab versus regorafenib in patients with previously treated metastatic colorectal cancer.

TPS3630 Background: Metastatic colorectal cancer (mCRC) is associated with poor prognosis and limited treatment options for patients who have progressed on first- and second-line chemotherapy. Regorafenib and trifluridine-tipiracil are approved in third- or later-line setting, but survival benefit is limited. Immune checkpoint inhibitor (ICI) therapy with nivolumab ± ipilimumab or single-agent pembrolizumab is approved in microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) mCRC; however, MSI-H mCRC is present in only ~5% patients. Phase 1/2 studies have evaluated the tyrosine kinase inhibitor (TKI) cabozantinib in combination with the ICIs atezolizumab and durvalumab and have demonstrated encouraging clinical activity, with data suggesting greater benefit in RAS wild-type (wt) versus RAS mutant (mut) mCRC (Abrams TA, et al. ASCO GI 2022:Abs 121; Saeed A, et al. ASCO GI 2022:Abs 135). XL092 is a TKI that targets MET, VEGFR2, and the TAM kinases AXL and MER, which are implicated in tumor growth, metastasis, angiogenesis, and immunosuppression of the tumor microenvironment. XL092 displays immunomodulatory properties that may promote an immunopermissive tumor microenvironment and its half-life of 16–22 hours is supportive of once daily (QD) dosing. The phase 3 STELLAR-303 study (NCT05425940) is evaluating the efficacy and safety of XL092 in combination with atezolizumab versus regorafenib in patients with microsatellite stable or microsatellite instability-low mCRC who have progressed after or are intolerant to standard of care (SOC) therapy. Methods: STELLAR-303 is a global, randomized, open-label, phase 3 study. Eligible patients are aged ≥18 years with non-MSI-H/dMMR mCRC (determined by tissue-based analysis) that is measurable per RECIST v1.1 and have an ECOG performance status of 0–1 and adequate organ function. Patients must have progressed during/after or be intolerant to SOC therapies for mCRC; prior regorafenib, trifluridine-tipiracil, or anti–PD-L1/PD-1 ICIs are not allowed. Patients are randomized 1:1 to XL092 100 mg PO QD + atezolizumab 1200 mg IV Q3W or to regorafenib 160 mg PO QD (21 days/28-day cycle); randomization is stratified by geographic region (Asia, other), RAS status (wt, mut), and liver metastases (yes, no). Enrollment of 600 patients is planned (400 RASwt, 200 RASmut). The primary endpoint is duration of overall survival (OS) in the RASwt population, with other efficacy endpoints (progression-free survival, objective response rate, and duration of response per RECIST v1.1 by investigator and change in tumor markers) assessed in the RASwt population and, with OS, in the RASmut populations and in all randomized patients. Additional endpoints will assess safety, quality of life, changes in biomarkers, pharmacokinetics, immunogenicity, and healthcare utilization. Enrollment is ongoing. Clinical trial information: NCT05425940 .

Trastuzumab deruxtecan (T-DXd) in patients (pts) with HER2-overexpressing/amplified (HER2+) metastatic colorectal cancer (mCRC): Primary results from the multicenter, randomized, phase 2 DESTINY-CRC02 study.

3501 Background: T-DXd (6.4 mg/kg, every 3 weeks [Q3W]) demonstrated antitumor activity in pts with HER2+ mCRC in DESTINY-CRC01 (Siena et al. Lancet Oncol. 2021). We present primary results of DESTINY-CRC02 (NCT04744831), which assessed the efficacy and safety of T-DXd (5.4 and 6.4 mg/kg) in pts with HER2+ mCRC. Methods: This was a multicenter phase 2 study. Eligible pts had centrally confirmed HER2+ (immunohistochemistry [IHC] 3+ or IHC 2+/in situ hybridization [ISH]+) mCRC. Pts with RAS wild-type (wt) or mutant (m) mCRC were eligible. Pts had received prior standard therapy, unless contraindicated; prior anti-HER2 therapy was allowed. In stage 1, 80 pts were randomized 1:1 to 5.4 (n = 40) or 6.4 (n = 40) mg/kg T-DXd Q3W. In stage 2, an additional 42 pts received 5.4 mg/kg T-DXd. Primary endpoint was confirmed objective response rate (cORR) by blinded independent central review (BICR). Secondary endpoints included duration of response (DoR), progression-free survival (PFS), overall survival (OS), and safety. Results: At data cutoff (Nov 1, 2022), most pts in the 5.4 and 6.4 mg/kg T-DXd arms had HER2 IHC 3+ (78.0% and 85.0%), RAS wt tumors (82.9% and 85.0%), and a median of 3 and 4 prior lines of therapy, respectively. cORR was 37.8% (95% CI, 27.3-49.2%) in the 5.4 mg/kg arm and 27.5% (95% CI, 14.6-43.9%) in the 6.4 mg/kg arm (all partial responses in both arms). Key efficacy data are shown in the Table: Grade ≥3 treatment-emergent adverse events (AEs) were observed in 41/83 pts (49.4%) and 23/39 pts (59.0%) in the 5.4 and 6.4 mg/kg T-DXd arms, respectively. Serious AEs were observed in 20/83 pts (24.1%) and 12/39 pts (30.8%) in the 5.4 and 6.4 mg/kg arms, respectively. Independently adjudicated drug-related interstitial lung disease occurred in 7/83 pts (8.4%) with 5.4 mg/kg T-DXd and 5/39 pts (12.8%) with 6.4 mg/kg T-DXd, and most events were grade 1/2 (1 grade 5 in the 6.4 mg/kg arm). Conclusions: T-DXd showed promising antitumor activity in pts with HER2+ mCRC at both 5.4 and 6.4 mg/kg doses. Antitumor efficacy was observed irrespective of RAS mutation status at 5.4 mg/kg T-DXd, and in those with prior anti-HER2 therapy. Overall, safety was consistent with the known safety profile of T-DXd and favored the 5.4 mg/kg dose. Clinical trial information: NCT04744831 . [Table: see text]

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.

Real-world treatment and outcomes of patients with metastatic BRAF mutant colorectal cancer.

BRAF mutation occurs in 5%-10% of metastatic colorectal cancers (mCRCs). Patients with BRAF mutant mCRC exhibit a specific metastatic pattern and poor prognosis. Survival outcomes are heterogeneous in cases of mCRC with a BRAF mutation. The optimal first-line therapy is still controversial. We retrospectively reviewed the medical records of patients with mCRC between June 2010 and December 2021. Clinicopathologic characteristics, treatment and BRAF mutation testing results were collected. Patients with a BRAF mutation were included. Kaplan-Meier methods and log-rank tests were used to analyze and compare survival. Cox proportional hazards regression was used to establish the predictive nomogram model. Of the 4475 mCRC, 261 have a BRAF mutation, including 240 V600E and 21 non-V600E mutants. The median overall survival (OS) was 18.2months in the BRAF V600E mutant group versus 38.0months in the non-V600E mutant group (p=0.022). ECOG score, tumor differentiation, liver metastasis, bone metastasis and primary tumor resection were independent prognostic factors for the OS of BRAF V600E mutant mCRC. A nomogram model was established using these factors. The median OS was 39.3m, 18.2m and 10.7m for the low-risk, intermediate-risk and high-risk groups defined by this model, respectively (p < 0.0001). Patients who received first-line triplet chemotherapy ± bevacizumab had comparable progression free survival (PFS) and OS compared with those treated with doublets ± bevacizumab. BRAF V600E mutant mCRCs exhibit unfavorable and heterogeneous prognosis. The first-line intensive chemotherapy did not confer a marked impact on the PFS and OS.

Immunotherapy in RAS mutant mCRC: Could CTLA-4 blockade increase the efficacy of anti PD-1 agents? Preliminary clinical results of the NERDY study.

218 Background: Immune checkpoint inhibitors (ICI) showed high efficacy in both first and subsequent lines in metastatic colorectal cancer with mismatch repair deficiency (dMMR-mCRC); however, they still fail in a minority of patients (pts). In non-preplanned analyses from previous studies, RAS mutations ( RASm) have been related to limited activity of ICI monotherapy (ICIm) as compared to ICI doublets (ICId) in dMMR-mCRC. Emerging data suggest different immunological features in presence of RASm, resulting in lower immunogenicity. Methods: NERDY is a retrospective, monocentric study designed to investigate the effect of ICIm and ICId on dMMR-mCRC basing on RASm. Pts with dMMR-mCRC treated with ICIm/ICId at our Institute were included. Clinical-pathological features for each patient were collected. On primary tumor specimens, proinflammatory pathways and CMS subgroup will be assessed by Nanostring and RNA-Seq respectively. The study is exploratory and no formal hypothesis has been postulated. Both PFS and OS were calculated with Kaplan-Meier. Cox proportional hazard model was adopted in the interaction tests. Primary objective was to assess OS and PFS according to RAS in dMMR-mCRC pts treated with ICIm or ICId. Secondary objectives were to describe the inflammatory infiltrate and TMB in dMMR-mCRC according to RAS status. Results: From June 2015 to January 2022, a total of 126 consecutive dMMR-mCRC pts treated with ICI were included, 33 RASm/93 RASwt. RASm pts were more frequently males (p=0.015) and younger (median age 47 vs 65). An imbalance was observed in sidedness (more right-CRC in RASwt than in RASm as BRAF effect, p=0.001) and timing of ICI (administered in later lines in RASm, p=0.013). No differences in ECOG-PS, histotype, disease burden, stage at diagnosis, treatment with ICIm vs ICId and best response. At a median follow up of 53.5 months (95%CI 34.7-56.9), a trend toward longer PFS in pts treated with ICId over ICIm was found in the overall population (HR 0.62; 95%CI 0.36-1.05; p=0.055), being significantly longer in RASm-only pts (HR 0.41; 95%CI 0.13-1.28; p=0.047) but not in RASwt-only pts (HR 0.64; 95%CI 0.34-1.20; p=0.139). No difference was observed in OS between ICId and ICIm in the overall population (HR 0.64; 95%CI 0.36-1.16; p=0.121), in RASwt (HR 0.59; 95%CI 0.29-1.20; p=0.132) nor in RASm pts (HR 0.59; 95%CI 0.19-1.78; p=0.275). Interaction test for RAS and ICI treatment type was not significant for PFS (HR 0.63; 95%CI 0.21-1.94; p=0.423) nor for OS (HR=1.00; 95%CI 0.29-3.41; p=0.999). Conclusions: Preliminary clinical results of the NERDY study suggest enhanced activity of ICId compared to ICIm in pts with RASm dMMR-mCRC. Further data are expected from pending translational analyses and a pre-planned adjunctive cohort from two other Italian centers will be used for external validation.

TRIDENTE trial: A phase II study of rechallenge with encorafenib, binimetinib, and cetuximab in patients with RAS wild-type/BRAF V600E–mutant metastatic colorectal cancer.

TPS264 Background: The BEACON CRC trial demonstrated survival benefit of combination therapy with encorafenib (ENCO) + cetuximab (CET) +/- binimetinib (BINI) in patients with RAS wild-type (WT)/ BRAF V600E mutant metastatic colorectal cancer (mCRC). However, prognosis of those patients still be poor after the refractoriness to the BEACON combination therapy. One of resistant mechanisms to BRAF inhibitor has been reported as MAPK alterations including RAS mutation, similar to those for anti-EGFR antibody in patients with RAS/ BRAF V600E WT mCRC. Promising results of rechallenge therapy with anti-EGFR antibody in patients with RAS/ BRAF V600E WT mCRC and with combination of BRAF inhibitor + MEK inhibitor in patients with BRAF V600 mutant melanoma suggest the treatment strategy of rechallenge therapy with the BEACON triplet therapy in patients with RAS WT/ BRAF V600E mutant mCRC. Methods: TRIDENTE trial is a multicenter phase II trial to assess efficacy and safety of rechallenge therapy with ENCO + BINI + CET in patients with RAS WT/ BRAF V600E mutant mCRC after the refractoriness to either the BEACON doublet or triplet therapy. Key eligibility criteria includes RAS WT/ BRAF V600E mutant mCRC; ≥ 20 years old; ECOG PS 0-1; refractory or intolerant to at least one fluoropyrimidine-based regimen (including irinotecan or oxaliplatin); refractory or intolerant to anti-PD-1 antibody if patients with MSI-high; history of previous combination therapy containing ENCO + CET with at least partial response by RECIST v1.1; confirmed disease progression within 4 weeks after last administration of previous ENCO; ≥ 4 months of period between the last administration of previous ENCO and the start of study treatment. Enrolled patients receive the combination therapy with ENCO (300 mg, QD), BINI (45 mg, BID), and CET (initially 400 mg/m2, and subsequently 250 mg/m2, QW) as the study treatment. Primary endpoint is the objective response rate (ORR) by investigators’ assessment in patients receiving at least one dose of study treatment. A target sample size is calculated to be 21 on the hypothesis that the threshold ORR is 3% and expected ORR is 20%, with a significant level of 5% (one-sided) and power of 80%. Secondary endpoint includes progression-free and overall survivals, disease control rate, and safety. Exploratory molecular analysis is performed using targeted next-generation sequencing in circulating-tumor DNA at the timepoints of baseline and discontinuation of study treatment. As of September 19, 2022, 8 patients have been enrolled. Clinical trial information: jRCTs031210511 .

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...

WJOG13219G: The Efficacy and Safety of FOLFOXIRI or Doublet plus Anti-VEGF Therapy in Previously Untreated BRAFV600E Mutant Metastatic Colorectal Cancer: A Multi-Institutional Registry-Based Study (BRACELET Study)

BackgroundThe real-world survival benefit of FOLFOXIRI (fluorouracil, leucovorin, oxaliplatin, and irinotecan) plus anti-VEGF therapy (Triplet) over doublet chemotherapy (Doublet) remains controversial in patients with BRAFV600E mutant metastatic colorectal cancer (mCRC). Patients and MethodsWJOG13219G was a multicenter, retrospective, registry-based study of patients with BRAFV600E mutant mCRC who received first-line triplet or doublet chemotherapy from January 2014 to December 2019 in Japan. Inverse probability of treatment weighting (IPTW) was used to adjust for patient background. ResultsThe analysis included 79 and 91 patients in the Triplet and Doublet groups, respectively. The Triplet group was significantly younger and had better performance status. No statistical difference was noted in progression-free survival (PFS; HR, 0.82; 95% CI, 0.60–1.13; P = .22) and overall survival (OS; HR, 0.88; 95% CI, 0.62–1.25; P = .48) between both groups. IPTW analysis also showed no difference between the 2 groups in PFS (HR, 0.86; 95% CI, 0.69–1.08; P = .20) and OS (HR, 0.93; 95% CI, 0.73–1.20; P = .59). The Triplet and Doublet groups had an objective response rate of 53% and 41%, respectively (P = .10). At least one grade 3 or 4 adverse event was seen in 51 (65%) and 43 (47%) patients in the Triplet and Doublet groups, respectively, with the incidence of neutropenia being significantly higher in the former. ConclusionTriplet therapy had no survival benefit versus doublet therapy in the overall and IPTW cohorts or specific subgroups for real-world patients with BRAFV600E mutant mCRC.

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.

P41-7 Two cases of BRAF mutant mCRC with intestinal stenosis responded to encorafenib + binimetinib + cetuximab: A case report

BRAF mutant metastatic Colorectal Cancer (mCRC) has a poor prognosis and response to chemotherapy. The oral agents, encorafenib and binimetinib in combination with cetuximab (BEACON-3) was approved as 2nd-line therapy for BRAF mutant mCRC in Japan. However, we often experience mCRC patients with intestinal stenosis. These patients may not be eligible for oral medication due to decline of drug absorption. We report two cases of BRAF mutant mCRC that developed intestinal stenosis during 1st-line therapy and responded to BEACON-3.

Prognostic and Predictive Value of PIK3CA Mutations in Metastatic Colorectal Cancer

Comprehensive genomic profiling is used to guide the management of metastatic colorectal cancer (mCRC); however, the role of PIK3CA mutations, present in up to 20% of mCRCs, is unclear. This study aimed to evaluate the association of PIK3CA mutations with other common mutations in mCRC and determine the prognostic and predictive value of PIK3CA mutations. A retrospective chart review was performed on patients in the Moffitt Clinical Genomic Database with mCRC. A meta-analysis was performed to further evaluate the predictive value of PIK3CA mutations to the response to anti-epidermal growth factor receptor (EGFR) therapy. Among 639 patients, PIK3CA was positively correlated with KRAS mutation (r=0.11, p=0.006) and negatively correlated with TP53 mutation (r=- 0.18, p≤0.001) and ERBB2 amplification (r=- 0.08, p=0.046). The median overall survival (OS) of patients with PIK3CA-mutant mCRC (n=49) was 35.5 (95% confidence interval [CI] 18.7-48.1) months vs. 55.3 (95% CI 47.5-65.6) months for PIK3CA wild-type mCRC (n=286) [p=0.003]. This OS difference remained significant with exon 9 and exon 20 subset analyses. There was no significant difference in response rate between patients with PIK3CA wild-type (n=97) versus mutant (n=9) mCRC who received anti-EGFR therapy (43% vs. 56%, p=0.61) and no significant difference in median progression-free survival (PFS) of 10.3 versus 7.2 months (p=0.60). However, our meta-analysis of 12 studies, including ours, using a common effect model identified that PIK3CA mutations are associated with reduced response to anti-EGFR therapy, with a relative risk of 0.56 (95% CI 0.38-0.82). Our study identified PIK3CA mutations as a poor prognostic factor, and our meta-analysis identified PIK3CA mutations as predictive of decreased response to anti-EGFR therapy in patients with mCRC.