mCRC Patients Research Articles

Rechallenge therapy versus tyrosine kinase inhibitor (TKI) for advanced metastatic colorectal cancer: a retrospective study

Currently, the standard third-line treatment options for advanced metastatic colorectal cancer (mCRC) include regorafenib, fruquintinib, and trifluridine/tipiracil (TAS-102), but these drugs have limited clinical efficacy. This study aims to evaluate the efficacy and survival outcomes of tyrosine kinase inhibitor (TKI) versus chemotherapy rechallenge in third-line treatment for advanced mCRC patients. From January 2019 to December 2022, 107 patients met the inclusion criteria. After 1:1 matching, there were 34 patients in both the TKI and rechallenge groups. Cox regression analysis was performed to identify independent predictive factors. The result indicated that Eastern Cooperative Oncology Group (ECOG) score of 0–1 (hazard ratio [HR] = 0.03, 95% confidence interval [CI]: 0.01–0.17; P < 0.001) and chemotherapy rechallenge (HR = 0.43, 95% CI: 0.23–0.79; P = 0.007) were independent protective factors for overall survival (OS). Patient-Generated Subjective Global Assessment (PG-SGA) score of 0–3 (HR = 0.43, 95% CI: 0.23–0.80; P = 0.008), progression-free survival (PFS) of frontline treatment (HR = 0.66, 95% CI: 0.43-1.00, P = 0.047) and chemotherapy rechallenge (HR = 0.42, 95% CI: 0.24–0.73; P = 0.002) were independent protective factors for PFS. Kaplan-Meier survival analysis showed that the median OS in the rechallenge group was 13.2 months (95% CI: 9.6–19.3), compared with 7.7 months (95% CI: 6.5–14.5) in the TKI group, with a statistically significant difference (HR = 0.47, 95% CI: 0.26–0.86; P = 0.013). The median PFS for the rechallenge group was 5.0 months (95% CI: 4.3–6.7), compared with 3.4 months (95% CI: 2.7–4.8) in the TKI group, with a statistically significant difference too (HR = 0.54, 95% CI: 0.32–0.91; P = 0.019). Furthermore, subgroup analysis showed that in Group A, the rechallenge group also had superior median OS and PFS compared with the TKI group. In conclusion, while TKIs are the current standard for third-line treatment in mCRC patients, chemotherapy rechallenge is a more effective option for patients who have achieved disease control in the first two lines of treatment.

Comparative efficacy of cetuximab combined with FOLFOX or CAPEOX in first-line treatment of RAS/BRAF wild-type metastatic colorectal cancer: a multicenter case-control study.

FOLFOX combined with cetuximab is a recommended first-line treatment regimen for RAS/BRAF wild-type metastatic colorectal cancer (mCRC). CAPEOX combined with cetuximab differs from the FOLFOX regimen by using oral capecitabine instead of continuous infusion of fluorouracil, offering greater convenience and cost-effectiveness with higher patient acceptance. However, the comparative efficacy of these two regimens remains debatable, necessitating further evidence to explore any differences in their efficacy. This study collected medical records of mCRC patients who were treated with CAPEOX or FOLFOX combined with cetuximab from 1 October 2021 to 16 October 2023 at Harbin Medical University Cancer Hospital and the First Hospital of Shanxi Medical University. Eligible patients were selected based on inclusion criteria and followed up through the hospital's follow-up system and telephone interviews. Kaplan-Meier survival analysis and Cox proportional hazards regression analysis were used to assess patients' progression-free survival (PFS) and overall survival (OS). A total of 71 eligible patients were enrolled in this study; 43 patients received CAPEOX combined with cetuximab (Group A, n = 43), and 28 patients received FOLFOX combined with cetuximab (Group B, n = 28). The two groups achieved similar median PFS (mPFS) and median OS (mOS), with mPFS of 18 months and 12 months, respectively (P = 0.23), and mOS of 33 months and 20 months, respectively (P = 0.21), with no statistically significant differences. The results of this study demonstrated that CAPEOX combined with cetuximab is an equally viable option for first-line treatment of RAS/BRAF wild-type mCRC as FOLFOX combined with cetuximab.

The prognostic utility of the ratio of lymphocyte to monocyte in patients with metastatic colorectal cancer: a systematic review and meta-analysis

BackgroundAlthough advancements in treatment have resulted in improved overall outcomes for patients diagnosed with colorectal cancer, the prognosis remains unfavorable for individuals with metastatic colorectal cancer (mCRC). The association between lymphocyte/monocyte ratio (LMR) and clinical outcomes in mCRC patients is a subject of controversy. To systematically evaluate the correlation between LMR and prognostic factors in individuals with mCRC, we conducted this meta-analysis.MethodsThe databases PubMed, Embase, Web of Science, and the Cochrane Library were systematically searched for all relevant studies from their inception until October 26, 2024. Study selection was conducted based on predetermined inclusion and exclusion criteria. The primary outcomes of interest included prognosis measures such as overall survival (OS), progression-free survival (PFS), disease-free survival (DFS), and cancer-specific survival (CSS) in patients with metastatic colorectal cancer. Random-effects models or fixed-effects models were used to determine the pooled risk ratio (HR) and corresponding 95% confidence interval (CI) for each outcome indicator. Additionally, the pooled odds ratio (OR) and its corresponding 95% CI were calculated for LMR and clinicopathological characteristics.ResultsFourteen studies involving 3,089 patients were included in the analysis. The pooled analysis found that high LMR was correlated with better OS (HR: 0.55, 95% CI: 0.49-0.62, p&amp;lt;0.00001), PFS (HR: 0.68, 95% CI: 0.57-0.81, p&amp;lt;0.0001) and CSS(HR: 0.55, 95% CI: 0.32-0.95, p=0.03),The prognostic value of high LMR values for DFS(HR: 0.93, 95% CI: 0.78-1.12, p=0.46) in patients with metastatic rectal cancer was not found to be significant. We performed subgroup analyses based on study characteristics to confirm the robustness of our findings. Further clinicopathological analysis showed no significant difference between patients with elevated LMR and those without elevated LMR.ConclusionsIn conclusion, the results demonstrate a robust correlation between elevated LMR levels and a favorable prognosis in terms of overall survival (OS), progression-free survival (PFS), and cancer-specific survival (CSS) among patients diagnosed with metastatic colorectal cancer. However, further high-quality prospective studies are warranted to validate our findings since the majority of current investigations have relied on retrospective study designs.Systematic review registrationhttps://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42024496467, identifier CRD42024496467.

Phase II study of trifluridine/tipiracil (TAS-102) plus irinotecan in combination with bevacizumab as a second‐line therapy for patients with metastatic colorectal cancer.

155 Background: Metastatic colorectal cancer (mCRC) patients have poor prognoses with limited response to second-line chemotherapy. Therefore, it is urgent to refine and design an optimal second-line treatment regimen to improve the response rate and prolong the survival of patients with mCRC. This study assessed the safety and efficacy of the trifluridine/tipiracil (TAS-102), irinotecan, and bevacizumab regimen in second-line settings for mCRC patients. Methods: This was a multicenter, single-arm, phase II trial. The mCRC patients who are refractory to standard first-line treatment, including fluoropyrimidine and oxaliplatin, are eligible. Based on the recommended phase II dose established in phase I, enrolled patients received TAS-102 (30 mg/m2 twice daily on days 1-5) and irinotecan (150 mg/m2 on day 1) combined with bevacizumab (5 mg/kg on day 1) every two weeks. The primary endpoint was the objective response rate (ORR). Results: Between October 1, 2023, and August 31, 2024, 60 patients were enrolled, and all of them were evaluated for efficacy. As of August 31, 2024, efficacy was assessed in all 60 participants with an ORR of 18.3% (2 had complete response, CR; 9 had partial response, PR; 39 had stable disease, SD). Among the 39 patients with SD, 29 patients experienced tumor shrinkage. The disease control rate (DCR) was 83.3%. The median follow-up was 8.6 months (95% confidence interval [CI], 6.743-10.457). The six-month progression-free survival (PFS) was 59.6%. The median PFS was 6.9 months (95% CI 5.016-8.784), whereas the median overall survival (OS) was not reached. The 1-year OS rate was 92%. At the time of analysis, four patients have died, and 56 patients are still alive. All patients were evaluable for safety assessment. The most common treatment-related adverse events (TRAE) were nausea (100%), neutropenia (86.7%), and anemia (83.3%). The most frequent grade 3/4 TRAE were neutropenia (48.3%), febrile neutropenia (8.3%), nausea (3.3%), and anemia (3.3%). No treatment-related death occurred. Conclusions: The regimen of irinotecan, TAS-102, plus bevacizumab preliminarily demonstrated promising efficacy with tolerable toxicity for mCRC patients as second‐line treatment. This regimen warrants further exploration in refractory mCRC patients. Clinical trial information: NCT06202001 .

Effect of homologous recombination deficiency on survival in patients with metastatic colorectal cancer with KRAS mutations.

252 Background: Metastatic colorectal cancer (mCRC) patients exhibit intertumoral genetic heterogeneity, making it difficult to apply precision medicine. In the molecular genetic profile of mCRC, there are relatively few other gene alterations that significantly impact treatment decisions beyond KRAS and MSI status. We aim to investigate the prognostic impact of Homologous recombination deficiency (HRD)-related genetic alterations in mCRC patients, focusing on how mutation status influences on patient outcomes. Methods: The analysis included 364 mCRC patients who underwent comprehensive genomic profiling at Korea University Anam Hospital from Sep. 2016 to Dec. 2020. HRD was defined by the presence of pathogenic variants in genes including ATM, ATR, BARD1, BRCA1/2, BRIP1, CDK12, CHEK2, FANCA, MRE11A, PALB2, RAD50/51. Overall survival (OS) and progression-free survival (PFS) were evaluated using the Kaplan-Meier method. Multivariate Cox proportional hazards regression analyses were performed to assess the independent impact of HRD status. Results: Of the total cohort, 181 of patients (49.78%) harbored KRAS mutations. HRD gene mutations were identified in 38 of patients (10.4%) of patients, predominantly in ATM, BRCA 1/2, ARID1A genes. KRAS-HRD co-mutations were present in 18 of patients (4.7%). There is no significant difference in HRD status between the KRAS mutant and wild-type groups (p=0.73). While first-line treatment PFS was independent of KRAS mutational status (wt 10.8 vs. mut 9.6 months, p=0.31), it was significantly associated with HRD gene mutation status (16.2 vs. 10.6 months, p=0.001). OS was similar with KRAS mutations (34.7 vs. 32.9 months, p=0.72) and HRD mutations (34.7 vs. 39.1 months, p=0.73). However, patients with both KRAS and HRD mutations had significantly worse OS compared to those with either KRAS and HRD mutation (21.3 vs. 36.7 vs. 65.3 months, p=0.034, &lt;0.001). A multivariate analysis was performed to evaluate factors affecting OS in mCRC patients. Among the variables, metastasectomy, which 44% of patients underwent, had a significantly low HR (=0.28) and would contributed to more favorable outcomes when evaluating OS. Neither KRAS nor HRD mutation alone was a significant prognostic factor, but their co-mutation was significantly associated with poor survival (HR=2.39, p=0.048). Conclusions: Poor OS in patients with KRAS-HRD co-mutations, despite metastasectomy, highlights the need for additional treatment strategies beyond surgery. Future studies with larger sample sizes and analyses stratified by metastasectomy status are necessary to strengthen these findings. Variables HR (95% CI) p-value Metastasis site Liver 2.16 (1.60 – 2.92) &lt; 0.001 Peritoneum 1.52 (1.01 – 2.11) 0.013 Bone 1.69 (0.96 – 2.97) 0.067 Metastasectomy 0.28 (0.47 – 0.74) &lt; 0.001 KRAS 1.03 (0.77 – 1.37) 0.826 HRD 0.75 (0.40 – 1.41) 0.367 Co-mutation 2.39 (1.01 – 5.66) 0.048

Phase II single-arm, single-center clinical trial of all-trans-retinoic acid, bevacizumab, and atezolizumab in refractory microsatellite stable colorectal cancer.

TPS324 Background: A critical clinical challenge in microsatellite stable (MSS) metastatic colorectal (mCRC) patients is to identify strategies to overcome lack of response to immune checkpoint inhibitors. An immunosuppressive tumor microenvironment comprising myeloid-derived suppressor cells (MDSC), endothelial cells, regulatory T cells, tumor associated macrophages, and cancer associated fibroblasts promotes immune evasion and resistance to these agents. MDSCs are bone marrow derived myeloid cells that suppress T-cell function and promote tumor growth. Among all cancers, mCRC patients have one of the highest frequency of MDSC (CD11b+, CD33+, CD14+ HLA-DRneg) in blood (1). It was demonstrated that altering the MDSC% in the tumor microenvironment by ATRA and anti-VEGF therapy (bevacizumab) can enhance the effects of immune checkpoint inhibitors (2-4). The hypothesis of the current clinical trial is that the combination of ATRA, bevacizumab and atezolizumab will lead to a decrease in MDSC population in tumor microenvironment leading to a clinically meaningful improvement in response rates among refractory MSS mCRC patients. Methods: This is a single-arm, open-label, phase 2 clinical trial combining ATRA, bevacizumab, and atezolizumab in refractory MSS mCRC patients. It will enroll a total of 21 patients over 24 months at UT Southwestern Medical Center that are MSS by PCR or NGS testing or are proficient in immunohistochemical expression of all four mismatch repair enzymes (MLH1, MSH2, MSH6, PMS2). ATRA will be administered orally at 45 mg/m2/day in 2 divided doses on days 1-7 and repeated every 14 days; atezolizumab will be given intravenously on day 1 at 840 mg dose every 14 days, and bevacizumab will be administered intravenously on day 1 at 10 mg/kg dose every 14 days. The first six patients enrolled on this study will contribute to the safety lead-in phase of this study. The primary outcome is to assess the overall response rate by RECIST v1.1. Secondary outcomes include assessment of disease control rate and frequency of adverse events using CTCAE v5.0. Exploratory outcomes include assessment of PFS and OS and collecting blood and tissue samples at defined timelines to study the changes in the MDSC population among responders and non-responders (NCT05999812). 1. Kobayashi, M. et. al., Clin Cancer Res, 2019. 2. Mirza, N., et al., Cancer Res, 2006. 3. Tobin, R.P., et al., Int Immunopharmacol, 2018. 4. Tobin, R.P., et. al., Clin Can Res, 2023. Clinical trial information: NCT05999812 .

Adjusting Treatment Strategies Using Circulating Tumor Cells: Preliminary Results on Metastatic Colorectal Cancer.

To assess the effectiveness of circulating tumor cells (CTCs) in proposing second-line treatments for metastatic colorectal cancer (mCRC). We analyzed CTCs from 21 patients (first group) with mCRC, for whom first-line treatment regimens were ineffective. CTCs were isolated and used for chemo-sensitivity/viability assays on several chemotherapeutic drugs. Based on these assays, a second-line treatment was recommended for each patient. Using overall survival (OS) as primary endpoint, statistical analysis was performed, comparing the survival of a group of 21 mCRC patients (first group) with the survival of 12 mCRC patients treated only with best supportive care (BSC) (second group), as well as with the survival estimated by meta-analysis of the BSC summary statistics (medians) published in various papers and clinical trials. Furthermore, the statistical significance of the difference between the two groups was examined by applying statistical tests that can deal efficiently with small datasets, non-proportional hazard patterns, and crossing curves, such as K-sample omnibus, MaxCombo, multiple-direction, and weighted log-rank tests. The median OS (mOS) for the first group (9 months) was found longer than the mOS of the BSC group (about 5 months). This result was further verified since the weighted mOS, estimated by meta-analysis, was found at 5.15 months. This difference was found statistically significant for central and late hazards. The preliminary results indicate that treatment based on CTCs' response in vitro prolongs mOS of mCRC patients compared with BSC patients, whereas a beneficial effect is gained for the prediction of treatment response in mCRC.

A retrospective observational study to evaluate the efficacy of trifluridine/tipiracil ± bevacizumab in metastatic colorectal cancer with MSI-high/deficient MMR.

152 Background: MSI-high (MSI-H)/deficient MMR (dMMR) metastatic colorectal cancer (mCRC) have reported to be resistant to various cytotoxic agents including fluorouracil. On the other hand, preclinical study showed that trifluridine was effective to fluorouracil-refractory dMMR CRC cell lines. Previous studies on trifluridine/tipiracil (FTD/TPI) ± bevacizumab (BEV) for mCRC as later line treatment showed an objective response rate (ORR) of 1.1-5.6% and disease control rate (DCR) of 44-76.6%. However, there are no reports on the efficacy of FTD/TPI± bevacizumab in MSI-H/dMMR mCRC patients. Methods: We retrospectively evaluated the efficacy and safety of FTD/TPI ± BEV as second- or later-line treatment which patients with MSI-H/dMMR mCRC received between June 2012 and January 2023 at the 10 institutions. The primary endpoint was investigator-assessed objective response rate (ORR). The secondary endpoints were progression-free survival (PFS), overall survival (OS), disease control rate (DCR), and adverse event rates. We also compared the FTD/TPI + BEV (FTB group) with FTD/TPI (FT group). Results: A total of 18 patients (FTB/FT, 9/9) were included. Patient characteristics were as follows (FTB/FT): median age, 70 (70/70) years; ECOG PS of 0/1, 7 (5/2)/11(4/7); primary tumor location of right side/left side, 12(6/6)/6(3/3); BRAF V600E mutant/wild-type, 6(3/3)/11(6/5); number of previous treatment lines of 1/≥2, 2(1/1)/16(8/8); number of metastatic sites of 1-2/≥3, 8(4/4)/10(5/5); prior use of anti-PD-1 therapy, 10(3/7). Efficacies in the whole population were as follows: ORR, 16.7% (95%CI, 3.6-41.4); DCR, 72.2%; median (m) PFS, 5.5 months; mOS, 11.8 months. Efficacies in each group (FTB vs. FT) were as follows: ORR (22.2% vs. 11.1%) and DCR (88.9% vs. 55.6%) were favored in FTB group than in FT group, while the median PFS were similar between two groups (5.6 months vs. 5.2 months). OS in FTB group was longer than in FT group (median, 18.9 months vs. 7.1 months; hazard ratio, 0.22; p value=0.03). Of 11 (FTB/FT, 7/4) patients who received subsequent treatment, 6 in FTB group and 1 in FT group received anti-PD-1 therapy. The most common grade 3 or more adverse events in each group (FTB vs. FT) were neutropenia (77.8% vs.77.8%), anemia (22.2% vs. 33.3%) and febrile neutropenia (0% vs. 22.2%). Conclusions: FTD/TPI ± BEV showed a promising efficacy and favorable safety. Although this was retrospective study with a small sample size, FTD/TPI ± BEV therapy may have better efficacies for MSI-H/dMMR mCRC than those for MSS/proficient MMR mCRC in previous prospective studies. Next generation sequencing as biomarker analysis using pretreated tissue samples is ongoing.

Real-world (RW) treatment patterns and clinical outcomes of patients treated with sequential regorafenib and trifluridine/tipiracil ± bevacizumab (BEV) for metastatic colorectal cancer (mCRC) in the United States (US) community oncology setting: The SEQRT2 study.

62 Background: Both Regorafenib (R) and Trifluridine/Tipiracil (T) ± BEV are widely used treatments for mCRC in later lines. This RW study evaluated optimal sequencing and associated outcomes among patients who initiated R and T in sequential lines of therapy (LOT) between LOT1-LOT6 within community oncology settings in the US. Methods: A retrospective study utilizing electronic medical record data from The US Oncology Network examined adult patients with mCRC who initiated R and T ± BEV sequentially between 09/01/2015 and 11/30/2022 (index date), with follow-up until 05/31/2023. Treatment patterns, overall survival (OS) and time to next treatment (TTNT) after sequence were assessed overall, R first (R-T) and T first (T-R). Multivariable Cox regression adjusting for age, sex, ECOG, tumor stage, and prior medication, assessed the association of factors with OS and TTNT. Results: In total, 308 mCRC patients initiating R and T (R-T, 156 pts [140 R-T and 16 R-T+BEV]; T-R, 152 pts [136 T-R and 16 T+BEV-R]) met study criteria. Baseline demographic (mean age 63 yrs, males 55%) and clinical characteristics (70% colon cancer, 58% ECOG 0-1) were similar between the cohorts. Most patients initiated index therapies at the third line of therapy (LOT3) (49% R-T, 45% T-R). The median (IQR) sequence duration was 7.4 (5.6), 6.7 (4.4), and 7.0 (4.7) months, respectively in patients with R-T, T-R, and overall. The median (95% CI) OS was 12.8 (11.2, 14.1) months among R-T and 10.2 (8.8, 11.9) months among T-R patients. Compared to R-T, the adjusted HR for the T-R sequence was 1.2 (95% CI 0.9–1.6; p=0.2). The median (95% CI) TTNT was 9.3 (8.4, 10.3) and 8.6 (7.8, 9.4) months, for R-T and T-R, respectively; the adjusted HR was 1.1 (95% CI 0.8–1.4; p=0.62). Conclusions: Patients initiating R first appeared to have a longer duration of treatment and survival, although not statistically significant. The one-year median duration of survival in this real-world setting confirms the importance of access to these treatments in patients with mCRC and can inform physicians regarding the choice of medications while sequencing therapies in mCRC. Clinical outcomes among R-T and T-R mCRC patients. Variable Level R-T (± BEV)[N 1 = 156] T (± BEV) -R[N 1 = 152] Adjusted 3,4 HR 5 (95% CI)[R-T Reference] Effect OverallSurvival Months – median (95% CI) 12.8(11.2, 14.1) 10.2(8.8, 11.9) 1.20 (0.91, 1.58) 0.20 TTNT 2 Months – median (95% CI) 9.3(8.4, 10.3) 8.6(7.8, 9.4) 1.07 (0.83, 1.37) 0.62 1 Entire R-T and T-R cohorts are presented since 16 patients in each cohort initiated T+BEV. 2 Time To Next Treatment. 3 Overall Survival adjusting for age, gender, stage at diagnosis, ECOG, prior anti-VEGF treatment. 4 Time To Next Treatment adjusting for age, gender, stage at diagnosis, and line of therapy. 5 Hazard Ratio.

Real-world analysis of the impact of timing of biomarker testing on first-line treatment choice in patients with metastatic colorectal cancer in British Columbia.

253 Background: The treatment landscape for metastatic colorectal cancer (mCRC) has evolved significantly, shifting from chemotherapy alone to more personalized approaches that include immune checkpoint inhibitors and targeted therapies. Treatment decisions in mCRC are driven by molecular characteristics, and current guidelines recommend a minimum standard of biomarker testing, such as mismatch repair (MMR) status, and RAS and BRAF mutations, at the time of metastatic disease diagnosis to guide treatment selection. This study aimed to assess the real-world implementation of biomarker testing in a contemporary cohort of mCRC patients in British Columbia (BC) and its impact on treatment decisions by medical oncologists. Methods: We conducted a retrospective chart review of patients who received first-line systemic therapy for mCRC in BC between January 2022 and December 2023. Patient demographics, tumour characteristics, and treatment details were obtained from the BC Cancer provincial pharmacy database. Medical oncology documentation and pathology reports were reviewed to determine the availability of biomarkers, including MMR status, and RAS and BRAF mutations (OncoPanel), at the time of initial medical oncology consultation, and to assess how these results influenced treatment plan. Results: To date, 71 eligible patients have been identified, with data collection ongoing. Of these, 82% had proficient MMR status, 17% had deficient MMR status, and 1% had incomplete data. RAS mutations were present in 55% of cases, while BRAF mutations were found in 21% (Table). At the time of the initial medical oncology consultation, MMR status was unavailable in 14 patients (20%), two of whom were later found to have deficient MMR status. OncoPanel results were unavailable for 63 patients (88%) at the time of the initial consultation, and in 16 of these cases (25%), the systemic therapy plan was modified once the results were received. Conclusions: Even in contemporary practice with publicly funded biomarker testing, the results for RAS and BRAF mutations were not available at the time of initial medical oncology consultation for most patients. Biomarker testing is an essential tool for guiding therapeutic decisions in mCRC. This subsequently led to treatment plan changes in one-quarter of cases after results were received. These findings highlight the importance of timely biomarker testing to ensure optimal and efficient treatment decision-making for all mCRC patients. Metastatic colorectal cancer biomarker testing. Proficient/WT Deficient/Mutated Incomplete MMR 58 12 1 RAS 29 39 3 BRAF 53 15 3

BXQ-350, a novel sphingolipid metabolism modulator, in combination with mFOLFOX7 and bevacizumab in newly diagnosed metastatic colorectal cancer (mCRC) patients: A phase 1b/2 randomized study.

TPS320 Background: Ceramides and sphingosine-1-phosphate (S1P) are key bioactive signaling molecules. Ceramides are proapoptotic and mitigate chemoresistance. Conversely, S1P promotes cancer cell proliferation, activates multiple oncogenic pathways, and stimulates immuno-suppressor cell populations promoting a pro-tumoral microenvironment. Several studies in colorectal cancer patients have shown high levels of ceramides are associated with improved survival, while high S1P levels are associated with a poor prognosis. Hence, modulation of sphingolipid metabolism could be a promising therapeutic approach. BXQ-350 is a nanovesicle of Saposin C, an allosteric activator of sphingolipid metabolism, that lowers systemic S1P and increases C18 ceramide. BXQ-350 was investigated in a Phase 1 dose-escalation safety study in cancer patients with advanced solid malignancies (NCT02859857). BXQ-350 was safe and well-tolerated (no DLT, no MTD). Also, 13 patients (~17.8% of evaluable patients) had a clinical benefit up to cycle 6 and beyond (PR, SD). Among patients with PFS &gt; 6 months, there were 4 recurrent CRC patients: 1 patient had a PFS of ~12 months, 2 of ~18 months, and 1 is still on study after 7 years suggesting potential long-term benefit. Furthermore, there were signs that BXQ-350 may alleviate symptoms of CIPN as 4 out of 10 patients with chronic CIPN at time of enrollment experienced an improvement of their symptoms. Methods: BXQ-350 is being investigated in a Phase 1b/2 study in combination with mFOLFOX7 and Bevacizumab in newly diagnosed mCRC patients (NCT05322590) to assess the efficacy and safety of BXQ-350. Design of the Phase 1b (open label study): 1) A safety dose escalation part to establish the RP2D: patients will initially receive 1.8 mg/kg BXQ-350 in combination with mFOLFOX7 and Bevacizumab. If safe (no MTD), dose of BXQ-350 will be increased to 2.4 mg/kg and 9 additional patients will be entered at this dose level. If safe, then this dose will be the RP2D and 21 additional patients will be enrolled, completing a 30 patient expansion cohort 2) Efficacy will then be evaluated for all patients entered at the RP2D. Primary objectives of the Phase 1b are to assess safety, identify RP2D, and assess preliminary efficacy of BXQ-350 in this combination. A secondary objective is to determine if BXQ-350 decreases CIPN. Enrollment in the expansion cohort of 30 patients is nearly complete, with 26 patients enrolled as of September 2024. Clinical trial information: NCT05322590 .

Exploratory study of TAS-102 combined with intermittent administration of fruquintinib in the treatment of third-line metastatic colorectal cancer.

174 Background: Fruquintinib and TAS-102 are two globally recognized standard therapies for mCRC patients who have previously undergone standard chemotherapy. A phase II exploratory study suggested that the combination of TAS-102 and fruquintinib could prolong progression-free survival (PFS) and overall survival (OS) in these patients. However, the benefits are sometimes limited due to tolerability issues associated with continuous dosing. This study aimed to investigate the efficacy and safety of intermittent administration of TAS-102 combined with fruquintinib as a third-line treatment for mCRC patients. Methods: This open-label, single-arm, single-center, exploratory clinical trial enrolled mCRC patients who had failed at least two standard treatment regimens. Eligible patients received oral fruquintinib (3 mg, once daily, on days 1-5 and 8-12) and TAS-102 (35 mg/m², twice daily, on days 1-5) every two weeks until disease progression or unacceptable toxicity occurred. The primary endpoint was objective response rate (ORR). Secondary endpoints included OS, PFS , DCR, and safety. Results: From August 2023 to September 2024, 26 eligible patients were enrolled. The median age of the patients was 58 years (range: 19-77), with 61.5% being female. RAS mutations were present in 57.7% of patients, 57.7% had left-sided colon or rectal cancer, 57.7% had liver metastases, and 76.9% had multiple metastases. As of September 10, 2024, 22 patients had undergone at least one tumor assessment, and 12 patients were still on treatment. Among them, 18.2% (4/22) achieved partial response , and 50% (11/22) had stable disease as the best response. Median PFS (mPFS) was 135 days (95% CI: 60.52-209.48). mPFS in RAS-mutant and RAS wild-type patients was 161 days (95% CI: 63.37-258.63) and 135 days (95% CI: 60.20-209.80), respectively, with ORRs of 25% and 12.5%. mPFS in patients with liver metastases (LM) and non-LM was 135 days (95% CI: 45.42-224.58) and 161 days (95% CI: 87.84-234.16), respectively, with ORRs of 14.3% and 25%. mPFS in patients with multiple metastases was 135 days (95% CI: 71.86-198.14), with an ORR of 17.6%. Median OS was not yet mature. Treatment-related adverse events (TRAEs) were generally manageable and tolerable. The most common hematological TRAEs (any grade, grades 3-4) included leukopenia (76.9%, 11.5%), neutropenia (73.1%, 11.5%), and anemia (53.8%, 7.7%). Non-hematological TRAEs were mostly grades 1-2, including anorexia (46.2%) and fatigue (19.2%). One case of grade 3 hypertension was reported. No treatment-related deaths were observed. Conclusion s: These preliminary results suggest that intermittent administration of TAS-102 in combination with fruquinitinib as a third-line treatment for patients with mCRC reduces hematological toxicity and is well tolerated, with encouraging clinical results. Clinical studies are ongoing. Clinical trial information: ChiCTR2300078241 .

Real-world outcomes of targeted therapies and local interventions in BRAF V600E–mutated metastatic colorectal cancer: A single-center retrospective study.

203 Background: Metastatic colorectal cancer (mCRC) patients with BRAF V600E mutations, especially those with microsatellite stable (MSS) tumors, have poor prognoses. Chemotherapy has limited efficacy in this subgroup, especially for second-line or subsequent-line treatments. Current research is increasingly focusing on the integration of targeted therapies and local interventions, but real-world evidence remains scarce, particularly from Asian cohorts. This study leverages real-world data to evaluate the impact of novel therapeutic combinations, including triplet and doublet targeted therapies, alongside local treatments in this high-risk patient population. Methods: This retrospective study includes MSS-type mCRC patients with BRAF V600E mutations treated at the Sixth Affiliated Hospital of Sun Yat-sen University between April 2014 and May 2024. Patients receiving targeted therapies were stratified into three groups: Triplet group (BRAF, EGFR, and MEK inhibitors, including Dabrafenib, Cetuximab and Trametinib), Doublet group (BRAF and EGFR inhibitors, including Dabrafenib and Cetuximab or Encorafenib and Cetuximab), and Doublet target-chemotherapy group (BRAF and EGFR inhibitors combined with chemotherapy, including Vemurafenib, Irinotecan, and Cetuximab). Primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS) and objective response rate (ORR). Results: Among 239 enrolled patients, 58 received targeted therapy and 68 underwent conventional chemotherapy as second-line treatment. 63.5% (80/126) of these patients underwent local interventions, including primary tumor resection, metastasectomy, CRS±HIPEC, and liver ablation. Targeted therapy demonstrated significantly improved mPFS compared to conventional chemotherapy (5.5 vs. 4.2 months, HR = 0.44; 95% CI: 0.29-0.68, p &lt; 0.001). OS did not differ significantly between the two treatment arms (12.7 vs. 12.1 months, HR = 0.80; 95% CI: 0.50-1.25, p = 0.330). In the triplet group, ORR, mPFS, and mOS were 21%, 5.8 months and 18.0 months, respectively, showing a trend towards enhanced efficacy compared to the other targeted therapy groups, albeit without statistical significance. Patients who received targeted therapy (n=35) or chemotherapy (n=45) in combination with local interventions demonstrated significantly prolonged OS compared to those without local therapy (mOS: 22.3 vs. 9.6 months; HR = 0.19; 95% CI: 0.09-0.42; p &lt; 0.001 and 14.3 vs. 10.9 months; HR = 0.53; 95% CI: 0.29-0.98; p = 0.042, respectively). Conclusions: Optimal treatment for BRAF V600E mCRC remains under investigation. This study suggests that combining targeted therapies with selective local interventions may significantly improve patient survival in this challenging subgroup, warranting further prospective evaluation.

Colorectal cancer metastatic dMMR immunotherapy (COMMIT) study: A randomized phase III study of atezolizumab (atezo) monotherapy versus mFOLFOX6/bevacizumab/atezo in the first-line treatment of patients with deficient DNA mismatch repair (dMMR) or microsatellite instability-high (MSI-H) metastatic colorectal cancer 9NRG-GI004/SWOG-S1610).

TPS311 Background: Approximately 45% of dMMR/MSI-H metastatic colorectal cancer (mCRC) in the immunotherapy arm progressed at 12 mos (KEYNOTE 177). We hypothesize that dMMR/MSI-H mCRC patients (pts) may be more effectively treated with the combination of PD-1/PD-L1 (PD-1) pathway blockade and mFOLFOX6/bevacizumab (bev) rather than with anti-PD-L1 therapy (atezo) alone. Preclinical work demonstrated synergistic effects between anti-PD-1/anti-VEGF as well as between oxaliplatin/anti-PD-1 in murine CRC models, and phase II data showed activity of anti-PD-1/anti-VEGF in chemotherapy refractory colon cancer. Within the AtezoTRIBE 8-pt dMMR CRC subgroup treated with FOLFOXIRI+bev+atezo, median PFS was not reached, with the first progression event at ~16 mos. Additionally, in other solid tumor malignancies, anti-PD-1 plus anti-VEGFr (i.e., HCC and RCC) as well as anti-PD-1 plus chemotherapy (i.e., gastroesophageal and lung cancers) combinations are standard first-line treatments. Methods: This two-arm prospective phase III open-label trial randomizes (1:1) mCRC dMMR/MSI-H to atezo monotherapy v mFOLFOX6/bev+atezo combination. Key inclusion criteria have been simplified on recent amendments to better mirror clinical practice for pts receiving mFOLFOX6/bev+atezo: One cycle of FOLFOX or CAPOX, with or without bev (or biosimilar) prior to enrollment allowed, dMMR tumor determined by local CLIA-certified IHC assay (MLH1/MSH2/MSH6/PMS2) or MSI-H by local CLIA-certified PCR or NGS panel; pts with total bilirubin ≤4.0 x ULN; duration of therapy for up to two years for both arms; imaging frequency on post-treatment follow-up has been reduced; as has measurable disease per RECIST. Primary endpoint is PFS. Assuming the atezo monotherapy control arm has a 48% PFS at 24 mos as assessed by site investigator, we have 80% power to detect a hazard ratio of 0.6 (equivalent to 64.4% PFS at 24 mos) with alpha 0.025 one-sided. Stratification factors include BRAFV600E status, metastatic site, and prior adjuvant CRC therapy. Secondary endpoints include overall survival, objective response rate, safety profile, disease control rate, and duration of response. Archived tumor tissue and blood samples will be collected for correlative studies. Harmonization of translational analyses is planned between GI004 (COMMIT) and A021502 (ATOMIC). Sample size has been modified with the accrual goal of 120 pts randomized between the two immunotherapy arms needed for study completion. Enrollment actively continues at U.S. sites. Current accrual (as of 9-20-2024): 100/120. Clinical trial information: NCT02997228 .

PK/PD analyses of circulating tumor DNA (ctDNA) in patients with metastatic colorectal cancer (mCRC) treated with telisotuzumab adizutecan (ABBV-400).

233 Background: Telisotuzumab adizutecan (ABBV-400) is an antibody drug conjugate (ADC) consisting of a c-Met targeting antibody telisotuzumab conjugated to a potent topoisomerase 1 inhibitor payload adizutecan. The ongoing first in human phase 1 trial (Study M21-404; NCT05029882) shows that ABBV-400 has encouraging radiographic response and ctDNA molecular response (MR) as monotherapy in patients with advanced solid tumors, including mCRC. Herein, correlation between ABBV-400 exposures and % change in ctDNA from baseline and PK/PD analyses using MR are presented for mCRC patients. Impact of c-MET expression and MET amplification ( MET -amp) status on exposures was also evaluated. Methods: Analyses utilized preliminary data in mCRC patients (N=122) from study M21-404 where subjects were treated with ABBV-400 (1.6 – 6.0 mg/kg Q3W). Serial PK samples were collected in cycles 1 (C1) and 3 (C3) and sparse samples across other cycles. C1 exposure metrics (C max , C avg , and C trough ) for both ABBV-400 conjugate and unconjugated payload were obtained by non-compartmental PK analysis. Baseline and C3 day 1 plasma samples were collected and analyzed using the Guardant INFINITY assay for biomarker analysis. ctDNA (circulating tumor fraction [cTF]) was estimated based on 1) variant allele frequency of somatic mutations in a 74 gene panel and 2) methylation signals across targeted regions of the Guardant INFINITY methylation panel. MR was defined as a 50% decrease in cTF from baseline. PK/PD correlations with % change in cTF at C3 and MR at C3 were evaluated. c-Met protein expression was assessed by IHC (VENTANA MET SP44 RxDx Assay) and MET -amp status was based on available local testing results and retrospective ctDNA testing. Results: Higher exposures of ABBV-400 conjugate and payload (primarily C avg for both analytes and C max for conjugate) correlated with greater decrease in % change in cTF at C3 from baseline, as assessed by the 74 gene panel (N =66) or methylation panel (N=74). PK/PD analysis showed that higher exposure was strongly correlated with higher probability of MR (n=66-74, nominal p &lt; 0.05). ABBV-400 conjugate and payload exposures were comparable across c-Met expression H-score (range 9 – 295), cut-offs (≥90% with 1+ intensity, ≥50% with 2+, ≥10% with 3+, ≥25% with 3+, and ≥50% with 3+), and MET -amp status. Conclusions: Exposure-response analyses have previously shown correlation between ABBV-400 conjugate exposures and probability of efficacy (objective response rate) as well as safety in mCRC subjects. The current PK/PD analyses demonstrate that higher ABBV-400 conjugate and payload exposures are also correlated with liquid biopsy data, i.e., ctDNA and MR based on ctDNA. c-MET expression and MET-amp did not have impact on ABBV-400 exposures. Clinical trial information: NCT05029882 .

Clinical validation of plasma circulating-tumor DNA assay using highly sensitive Safe-SeqS technology for detecting RAS and BRAF V600E in metastatic colorectal cancer.

50 Background: We developed a circulating-tumor DNA (ctDNA) test assay for RAS/BRAF mutations using next-generation sequencing-based Safe-SeqS technology. The clinical performance of detecting RAS and BRAF mutations were evaluated versus approved liquid biopsy and tissue testing, respectively. Methods: Metastatic colorectal cancer (mCRC) patients (pts) were enrolled. The concordance of the RAS mutational status in ctDNA between Safe-SeqS assay and OncoBEAM RAS CRC kit, which is approved as a companion diagnostic in Japan, was evaluated using archival plasma samples. The primary endpoints were positive percent agreement (PPA) and negative percent agreement (NPA). The concordance of the BRAF V600E mutational status between plasma-Safe-SeqS assay and tissue-based testing using MEBGEN RASKET-B kit, which is approved as a companion diagnostic in Japan, was prospectively evaluated. The primary endpoints were sensitivity and specificity of Safe-SeqS assay compared to tissue-based testing. Multivariate analysis using LASSO regression model was performed to evaluate the discordance of BRAF V600E mutational status between Safe-SeqS assay and tissue-based testing. Results: In 125 eligible plasma samples, the PPA and NPA for RAS mutational status in ctDNA were 87.1% (95% confidence interval [CI]: 76.1–94.3) and 95.2% (95% CI: 86.7–99.0), respectively. On the other hand, in 103 eligible pts, the sensitivity and specificity of Safe-SeqS assay for BRAF V600E mutational status were 69.2% (95% CI: 48.2–85.7) and 98.7% (95% CI: 93.0–100.0), respectively. Multivariate analysis revealed the baseline longest diameter and the number of lesions in pts with peritoneal and/or lung metastasis were factors associated with discordance. The sensitivity for BRAF V600E mutations increased to 81.0% (95% CI: 58.1–94.6, fisher’s exact test p =0.02) when the 5 pts with lower tumor burden (peritoneal metastasis with the longest diameter &lt;20 mm, and lung metastasis with the longest diameter &lt;20 mm and &lt;10 lesions, according to the previous report [1] ) were excluded. Conclusions: The clinical validity of the ctDNA assay for detecting RAS/BRAF V600E mutations using Safe-SeqS technology was confirmed in pts with mCRC. Careful attention should be paid for mCRC pts with only peritoneal and/or lung metastases having fewer metastases or smaller diameter lesions. 1. Kagawa Y, et al. Clin Cancer Res 2021.

A cross-sectional analysis from a real-world cohort of patients with microsatellite instability colorectal cancer (MSI-CRC) with metastatic disease from the Spanish RETUD registry.

178 Background: Survival of microsatellite instability (MSI) metastatic colorectal cancer (mCRC) patients (pts) has remarkably increased with immune checkpoint inhibitors (ICI). Here, we present our real-world data regarding the management and clinical outcomes of a cohort of 214 MSI-mCRC patients included in the Spanish Group of Treatment of Digestive Tumors TTD Registry (RETUD). Methods: RETUD is a national, multicenter registry for gastrointestinal tumors from the Spanish TTD Group. In this cross-sectional analysis we evaluated a real-world cohort of MSI-mCRC pts diagnosed from 1 st January 2017 to 29 th April 2024. Baseline characteristics, treatments and treatment response are descriptively presented. Tumoral response was evaluated according to RECIST 1.1 criteria. First line progression-free survival (PFS) and overall survival (OS) analyzed by Kaplan-Meier method are presented along with 95% confidence intervals (CI). Results: Among 679 MSI-CRC pts included in RETUD, a total of 214 mCRC pts were evaluable. Pts’ age at diagnosis was 69.6 (26-96) years, and they were predominantly Caucasian (97.7%) and female (53.7%). Eastern Cooperative Oncology Group (ECOG) performance status was 0-1 for 168 (78.5%) pts. Seventeen (10.7%) pts presented Lynch syndrome. Main tumor biological characteristics are described at Table 1 and the molecular profile (when available) was: KRAS mutation (24.3%), NRAS mutation (3.5%) and BRAF v600E mutation (53.0%). Surgical resections: 158 (73.8%) pts for primary tumor and 42 (19.6%) pts for metastasis. First line systemic treatment was administered to 187 (97.1%) pts: 92 (49.2%) pembrolizumab, 83 (44.4%) chemotherapy (CT), 4 (2.1%) other ICIs, 8 (4.3%) not reported. With a median follow up period of 17.4 months, the median (95% CI) OS and first-line PFS of the total mCRC population were 32.6 (22-72.4) and 11.1 (8.2-17.9) months (m), respectively. In immunotherapy (IT) pts mOS was not achieved (22.0-NA) and PFS was 26.5 m (12.9-NA) while the mOS was 28.9 m (16.3-69.3) and PFS 7.5 (5.4-9.3) m in CT pts. The overall response rate (ORR) was 54.2% in IT pts vs. 37.3% in CT pts. Conclusions: The introduction of IT has changed the evolution of MSI-H mCRC management, offering a beneficial impact in the OS and PFS survival in contrast to other conventional therapies in a real-world context. Tumor characteristics at initial diagnosis of CRC. Stage at initial diagnosis of CRC I/II, n (%) 4 (1.9) / 26 (12.1) III/IV, n (%) 66 (30.8) / 118 (55.1) Location of primary tumor a , n (%) right colon /left colon /rectum 160 (74.8) /37 (17.3) /19 (8.9) Main metastatic location b , n (%) Liver 84 (39.3) Peritoneal 76 (35.5) Lymph 71 (33.2) Lungs 41 (19.2) a Pts with more than 1 primary tumor; the percentage may be over 100%. Data missing for 4 (1.9%) pts. b Pts with more than 1 metastatic site; the percentage may be over 100%.

Evaluation of CSF1R as a potential prognostic biomarker in colorectal cancer (Alliance).

285 Background: Immune checkpoint inhibitors (ICIs) have shown limited efficacy in colorectal cancer (CRC) outside of mismatch repair (MMR) deficient/microsatellite instability-high (MSI-H) tumors. Most CRC cases are MMR proficient /microsatellite stable and demonstrate resistance to ICIs, attributed to the tumor microenvironment. Colony Stimulating Factor 1 Receptor (CSF1R), a regulator of tumor-associated macrophages, has emerged as a potential target due to its association with poor prognosis in CRC. Methods: Data from 433 metastatic CRC (mCRC) patients in the CALGB/SWOG 80405 trial were analyzed. CSF1R RNA was extracted from formalin-fixed, paraffin-embedded tumor samples and sequenced. Patients were divided into tertiles of CSF1R expression (high, medium, low). Progression-free survival (PFS) and overall survival (OS) were compared using Kaplan-Meier curves, log-rank tests, and Cox proportional hazards models. Subgroup analyses were conducted based on liver metastases, treatment type (Bevacizumab, Cetuximab, FOLFOX, FOLFIRI), and MSI status. Results: Low CSF1R expression (CSF1R-L) was associated with significantly better survival outcomes. Median PFS was 12.9 months for CSF1R-L, compared to 11.2 and 9.2 months for CSF1R-M and CSF1R-H (p = 0.003). Median OS was 35.8 months for CSF1R-L versus 32.5 and 24.4 months for CSF1R-M and CSF1R-H (p = 0.00086). Stratification by liver metastases showed that CSF1R-L remained a strong prognostic factor only in patients with liver metastases. There were no significant survival differences based on CSF1R expression in bevacizumab-treated patients. However, in cetuximab-treated patients, CSF1R-L tumors had significantly longer PFS (12.9 vs 8.8 months, p = 0.037) and OS (35.8 vs 21.4 months, p = 0.002) than CSF1R-H tumors. Similarly, in FOLFOX-treated patients, CSF1R-L tumors showed longer PFS and OS (p = 0.018 and p = 0.013, respectively), and in FOLFIRI-treated patients, OS was significantly longer for CSF1R-L tumors (42.2 vs 24.7 months, p = 0.022) than CSF1R-H tumors. Conclusions: Our data suggests that CSF1R expression may serve as a prognostic biomarker in CRC, with lower expression potentially linked to improved survival, particularly in patients with liver metastases. These findings warrant further investigation of CSF1R as a possible prognostic and predictive biomarker, as well as a potential therapeutic target in CRC. Clinical trial information: NCT00265850 .

Landscape of metastatic colorectal cancer (CRC) using comprehensive circulating tumor DNA (ctDNA) next-generation sequencing (NGS) in India: Expanding beyond RAS and RAF.

49 Background: Traditional testing in mCRC primarily focuses on RAS and RAF mutations. However, a broader range of emerging biomarkers, collectively termed the "Pressing panel" (PP), identifies patients with RAS/RAF wild-type (wt) tumors who may particularly benefit from anti-EGFR therapy. Comprehensive liquid biopsies provide a non-invasive method for identifying traditional and emerging biomarkers. Limited genomic data, including the prevalence of PP alterations (alts), is available for mCRC patients in India tested by ctDNA NGS. Methods: We reviewed the results of Guardant360 (Guardant Health, Inc.) ordered for patients with mCRC as part of routine clinical practice in India through July 2024. NGS analyzed plasma samples at a CLIA-certified, CAP-accredited central laboratory. Guardant360 analyzes ctDNA for mutations (mts), insertions and deletions, amplifications (amps), and fusions in up to 83 genes, including PP genes, i.e., KRAS, NRAS, BRAF, ERBB2, PIK3CA, PTEN, AKT1, ALK, ROS1, NTRK, RET, and MSI status. The Indian cohort's prevalence of PP mts was compared to that from other countries in Asia and Middle East (AME). Timing of testing relative to line of therapy was unknown. Results: Among 145 samples from India, ctDNA was detected in 92% (n=134). Median age was 59 years, with women comprising 40%. The median turnaround time from blood collection to result was 7 days. The mean mts count per sample was 5, and the median variant allele frequency was 1.5%. Frequent mts were in APC (53%), KRAS (56%), and SMAD4 (13%), while amps of EGFR (16%) and FGFR1 (9%) were common. Clinically relevant fusions were observed in 3% of patients. KRAS, NRAS, and/or BRAF V600E alterations were found in 63% of both India and AME samples. PP alts were identified in 24% and 27% of Indian and AME patients, respectively. Most frequent PP alts included PIK3CA (15%), PTEN (3%), and MET amp (2%). The prevalence of most of the PP alts was similar between the Indian and AME cohorts (Table), with minor differences observed in PIK3CA (15% vs 18%) and MSI-High (3% vs 1%). In patients with RAS/RAF wild-type lacking EGFR-amp, 9.5% (India) and 18% (AME) harbored at least one PP alt. Conclusions: This study highlights the role of liquid CGP for characterizing the mutational landscape and identifying PP mts for patients from India with advanced CRC. Pressing panel alterations. PP Alteration INDIA % (n=134) AME % (n=720) ERBB2 Amp 1% 2% MET Amp 2% 3% ALK Fusion 0% 0% ROS1 Fusion 0% 0% NTRK1 Fusion 1% 0% RET Fusion 0% 1% ERBB2 Mut 1% 2% PIK3CA Mut 15% 18% PTEN Mut 3% 3% AKT1 Mut 0% 1% MSI-High 3% 1%

Plasma shallow whole-genome sequencing profiling in patients with RAS WT metastatic colorectal cancer (mCRC) undergoing first-line anti-EGFR therapy.

214 Background: Acquired resistance (AR) to first-line (1L) chemotherapy (CT) + anti-EGFR inhibitors is a major challenge in the management of RAS WT mCRC patients (pts). While AR in later lines has been explained with point mutations in the EGFR pathway, its real mechanisms in 1L remain poorly understood. Tumor molecular biology can be dynamically studied through circulating tumor DNA (ctDNA) analysis, a real-time, non-invasive approach to detect AR. In this context, we conducted the multicenter prospective PLATFORM-B study, which enrolled 100 RAS WT mCRC pts receiving 1L CT + cetuximab across 15 Spanish Medical Oncology Departments, alongside 30 RAS MUT pts (control) treated with 1L CT + bevacizumab. Peripheral blood samples have been collected at baseline (BL), week 8, and disease progression (PD). Next-generation sequencing analysis (Ion S5 system) of ctDNA at PD revealed AR mutations in only 10% of pts, suggesting that alterations in the EGFR pathway may only partially explain AR in 1L. Therefore, we conducted shallow whole-genome sequencing (shWGS) to further characterize genomic profiles possibly related with novel mechanisms of AR. Methods: Baseline and PD samples with sufficient remaining plasma were considered for this analysis. shWGS was performed with a coverage ranging 0.5X to 2.0X and analyzed using ichorCNA pipeline to evaluate various genomic characteristics such as copy number alterations (CNA), tumor fraction (TF), subclonal fraction (SF), and ploidy. Molecular results were correlated to clinical-pathological features and outcomes. Results: Overall, 35 mCRC pts (27 RAS WT and 8 RAS MUT ) were included in the study. At BL ( N = 26), median TF (mTF) was 0.19, median ploidy 2, median SC fraction 0.5, median SC genome fraction 0.21, and median subclonal CNA fraction 0.41. At PD ( N = 33), mTF was 0.08, median ploidy 2, median SC fraction 0.5, median SC genome fraction 0.17, and median subclonal CNA fraction 0.38. Of all the features analyzed, only the TF showed potential prognostic value. At BL, pts with TF levels above the median had poorer overall survival (OS) compared to those with lower levels, approaching statistical significance ( P = .055). At PD, higher TF levels were statistically significantly associated with worse OS ( P = .02). No meaningful differences between the RAS WT and RAS MUT groups were observed. Specific variations in CNA, TF, SF, or ploidy under treatment are being correlated to clinical data to seek for predictive value. Conclusions: This preliminary analysis of the PLATFORM-B using shWGS showed the prognostic value of TF. Further analyses are undergoing to better understand the molecular landscape of acquired resistance to 1L anti-EGFR-based therapy in RAS WT mCRC pts.