Tabernero, Josep

Abstract Purpose: Routine testing for mismatch repair deficiency (dMMR)/microsatellite instability (MSI) in colorectal cancers is recommended for Lynch syndrome screening, prognosis, and treatment guidance. In the metastatic setting, RAS/BRAF mutations guide treatment decisions. The impact of these mutations on the tumor immune microenvironment (TiME) in MSI/dMMR colorectal cancer is not known. Experimental Design: The study involved retrospective analysis of 448 patients with stage I to IV MSI/dMMR colorectal cancer profiled using next-generation sequencing (Tempus xT DNA sequencing of 595–648 genes at 500x coverage and Tempus xR whole-exome capture RNA sequencing). MSI status was determined by assessing 44 or 239 loci using next-generation sequencing. dMMR was determined using IHC. Tumor mutational burden, tumor neoantigen burden (NTB), PD-L1, immune infiltration, and canonical immune pathways (76 gene set signatures) were analyzed. Results: The median age at diagnosis was 67 years (range, 21–86); 59% of patients were female, and 70% were stage III to IV. Among the 448 patients, 100 (22%) harbored RAS mutations (RASmut), 119 (27%) a BRAFV600E mutation, and 229 (51%) were double wild type. RASmut exhibited lower NTB (median, 12 vs. 15 vs. 16; P = 0.003) and PD-L1 (3.6% vs. 13% vs. 24%; P < 0.001) than BRAFV600E and wild-type tumors, respectively. The RASmut TiME had lower overall inflammation and fewer infiltrating CD8+ T cells than wild-type or BRAFV600E tumors. In contrast, BRAFV600E tumors exhibited hyperproliferative characteristics associated with broad metabolic reprogramming but a similarly inflamed TiME compared with wild-type tumors. Conclusions: Our data suggest that MSI/dMMR colorectal cancers harboring RASmut are less immunogenic, and the TiME contains a lower inflammatory profile than wild-type or BRAFV600E tumors. Further analysis and validation are required to confirm these findings.

LBA3500 Background: BREAKWATER (NCT04607421) is an open-label, global, randomized, phase 3 study evaluating first-line (1L) encorafenib + cetuximab (EC) ± chemotherapy (chemo) vs standard of care (SOC; chemo ± bevacizumab) in BRAF V600E-mutant metastatic colorectal cancer (mCRC). The study previously met one of its dual primary endpoints (EPs) demonstrating clinically meaningful and statistically significant improvement in confirmed objective response rate (ORR) by blinded independent central review (BICR) in the ORR subset. These results were the basis for the FDA accelerated approval of EC+mFOLFOX6 for BRAF V600E-mutant mCRC, including in the 1L, under Project Frontrunner. Here, we report the primary analysis of progression-free survival (PFS) by BICR, updated interim analysis of OS, updated safety, and other analyses. Methods: Eligible patients (pts) with untreated BRAF V600E-mutant mCRC were randomized 1:1:1 to receive EC, EC+mFOLFOX6, or SOC; EC arm enrollment was closed after a protocol amendment. Dual primary EPs: ORR and PFS by BICR (EC+mFOLFOX6 vs SOC); key secondary EP: OS (EC+mFOLFOX6 vs SOC). Results: 637 pts were randomized to EC, EC+mFOLFOX6, or SOC. Baseline demographics and disease characteristics were generally balanced between arms. EC+mFOLFOX6 (data cutoff: Jan 6, 2025) demonstrated a clinically meaningful and statistically significant PFS improvement vs SOC, meeting the other dual primary EP; HR=0.53 (95% CI 0.407, 0.677; P<0.0001); median PFS 12.8 vs 7.1 mo. OS was clinically meaningful and statistically significant vs SOC; HR=0.49 (95% CI 0.375, 0.632; P<0.0001); median OS 30.3 vs 15.1 mo. Median PFS and OS in the EC arm were 6.8 and 19.5 mo. These data and response data for all randomized pts are shown in the table. Serious treatment-emergent adverse events occurred in 30%, 46%, and 39% of pts in the safety analysis set. Safety was consistent with that known for each agent. Conclusions: BREAKWATER demonstrated clinically meaningful and statistically significant PFS and OS improvements with EC+mFOLFOX6 vs SOC and manageable toxicities. EC+mFOLFOX6 is potentially practice changing as the new SOC. Clinical trial information: NCT04607421 . ECn=158 EC+mFOLFOX6n=236 SOCn=243 EC+mFOLFOX6vs SOCHR (95% CI)P-value a Median PFS b , mo (95% CI) 6.8(5.7, 8.3) 12.8(11.2, 15.9) 7.1(6.8, 8.5) 0.53 (0.407, 0.677) <0.0001 Median OS, mo (95% CI) 19.5(17.6, 22.5) 30.3(21.7, NE) 15.1(13.7, 17.7) 0.49 (0.375, 0.632)<0.0001 ORR, b % (95% CI) 45.6(38.0, 53.3) 65.7(59.4, 71.4) 37.4(31.6, 43.7) Median DOR b , mo (95% CI) c 7.0 (4.2, 11.6) 13.9 (10.9, 18.5) 10.8 (7.6, 13.4) DOR b ≥6 mo, n (%) c 29 (40.3) 110 (71.0) 38 (41.8) DOR b ≥12 mo, n (%) c 15 (20.8) 54 (34.8) 16 (17.6) Median time to response, b wk (range) c 6.6(4.3-86.4) 7.0(5.1-103.6) 7.3 (5.4-48.0) a 1-sided stratified log rank test. b By BICR. c Responders: n=72, n=155, and n=91. DOR, duration of response.

PURPOSE Several lines of treatment can be used sequentially in patients with metastatic colorectal cancer. We investigated the evolution of patient/tumor characteristics and their prognostic impact across treatment lines to develop an overall prognostic score (OPS). PATIENTS AND METHODS Individual patient data from 48 randomized trials were analyzed. The end point was overall survival (from random assignment to death). Missing data were imputed. The complete data set was then separated into construction (80%) and validation sets (20%). The Cox's model was used to define risk groups for survival using the OPS. The discrimination capability was assessed in each treatment-line via bootstrapping to obtain optimism-corrected calibration and discrimination C-indices. Internal validation was done in the validation set. RESULTS A total of 37,560 patients (26,974 in first-line [1L], 7,693 in second-line [2L], and 2,893 in third-line [3L]) were analyzed. Some clinical, biological, and molecular characteristics of patients/tumors included in therapeutic trials evolve over the lines. Seven independent prognostic variables were retained in the final multivariate model common to all lines: Eastern Cooperative Oncology Group performance status, hemoglobin, platelet count, WBC/absolute neutrophil count ratio, lactate dehydrogenase, alkaline phosphatase, and the number of metastatic sites. The OPS was used to define four patient subgroups with significantly different prognoses in 1L, 2L, and 3L, separately, with adequate C-indices: 0.65, 0.66, and 0.69 in the construction set and 0.65, 0.66, and 0.68 in the validation set, respectively. The OPS was not predictive, with 3L drugs ( v placebo) or subsequent line (2L/1L or 3L/2L) extending survival in all prognostic groups. CONCLUSION The same prognostic model using practical variables can be used before all treatment lines. The OPS could better stratify patients in future clinical trials and help to therapeutic decision in routine practice.

3579 Background: Fruquintinib (F) is a highly selective, oral tyrosine kinase inhibitor of all 3 VEGF receptors. Based on FRESCO (NCT02314819) and FRESCO-2 (NCT04322539) data, F was approved by the US FDA for previously treatedmetastatic colorectal cancer (mCRC). Efficacy and safety of F + best supportive care (BSC) vs placebo (P) + BSC were analyzed according to prior treatment (tx) sequence using FRESCO and FRESCO-2 data. Methods: In FRESCO and FRESCO-2, patients (pts) were randomized 2:1 to receive F 5 mg or matching P, PO daily x 21 days every 28 days. In FRESCO, eligible pts had received ≥2 prior chemotherapy regimens and were permitted to have received prior anti-VEGF and/or anti-EGFR therapies, whereas in FRESCO-2, in addition to standard chemotherapies, anti-VEGF, and anti-EGFR therapies if indicated, prior exposure to trifluridine/tipiracil (TAS) and/or regorafenib (rego) was required. FRESCO-2 pts must have also received a BRAF inhibitor and/or immunotherapy, if indicated and available in their country. Results: In FRESCO (F n=278 vs P n=138), no pts had received rego and 16/416 pts (4%) had received TAS. InFRESCO-2, prior therapies were balanced between F vs P arms; pts had received prior TAS or rego in these sequences: prior TAS only (n=240 vs n=121); prior rego only (n=40 vs n=18); prior rego then TAS (n=84 vs n=45); prior TAS then rego (n=95 vs n=44). Improvements in OS and PFS were seen with F vs P regardless of prior tx sequence (Table), with similar magnitudes of benefit for OS (HRs 0.53–0.77) and PFS (HRs 0.25–0.37). F safety profile was consistent regardless of prior tx sequence (Table). Conclusions: F is effective in mCRC with a manageable safety profile regardless of prior TAS or rego tx and sequence. Improvement with F was similar for OS and PFS despite the number and sequence of prior regimens. F provides a new tx option for pts with previously treated mCRC regardless of prior TAS or rego exposure. Clinical trial information: NCT04322539 . [Table: see text]

Background Standard first-line therapies for metastatic colorectal cancer (mCRC) include fluoropyrimidine-containing regimens with oxaliplatin and/or irinotecan and a biologic agent. Immunotherapy may enhance antitumor activity in combination with standard therapies in patients with mCRC. Here, we present phase 2 results of nivolumab plus standard-of-care therapy (SOC; 5-fluorouracil/leucovorin/oxaliplatin/bevacizumab) versus SOC in the first-line treatment of patients with mCRC (CheckMate 9X8). Methods CheckMate 9X8 was a multicenter, open-label, randomized, phase 2/3 trial. Eligible patients were at least 18 years of age with unresectable mCRC and no prior chemotherapy for metastatic disease. Patients were randomized 2:1 to receive nivolumab 240 mg plus SOC or SOC alone every 2 weeks. The primary endpoint was progression-free survival (PFS) by blinded independent central review (BICR) per Response Evaluation Criteria in Solid Tumors V.1.1. Secondary endpoints included PFS by investigator assessment; objective response rate (ORR), disease control rate, duration of response, and time to response, all by BICR and investigator assessments; overall survival; and safety. Preplanned exploratory biomarker analyses were also performed. Results From February 2018 through April 2019, 310 patients were enrolled, of which 195 patients were randomized to nivolumab plus SOC (n=127) or SOC (n=68). At 21.5-month minimum follow-up, PFS with nivolumab plus SOC versus SOC did not meet the prespecified threshold for statistical significance; median PFS by BICR was 11.9 months in both arms (HR, 0.81 (95% CI, 0.53 to 1.23); p=0.30). Higher PFS rates after 12 months (18 months: 28% vs 9%), higher ORR (60% vs 46%), and durable responses (median 12.9 vs 9.3 months) were observed with nivolumab plus SOC versus SOC. Grade 3–4 treatment-related adverse events were reported in 75% versus 48% of patients; no new safety signals were identified. Conclusions The CheckMate 9X8 trial investigating first-line nivolumab plus SOC versus SOC in patients with mCRC did not meet its primary endpoint of PFS by BICR. Nivolumab plus SOC showed numerically higher PFS rates after 12 months, a higher response rate, and more durable responses compared with SOC alone, with acceptable safety. Further investigation to identify subgroups of patients with mCRC that may benefit from nivolumab plus SOC versus SOC in the first-line setting is warranted. Trial registration number NCT03414983 .

3554 Background: Approximately 30% of patients (pts) diagnosed with colorectal cancer (CRC) develop liver metastases (LM). Liver is the most common organ of metastasis of CRC. The ARCAD database contains individual patient data of randomized trials that included CRC pts with initially unresectable metastases treated with systemic therapy. The aim of this study was to assess the response and survival outcomes in non-LM (NLM) vs LM across different lines of treatment. Methods: We analyzed survival outcomes of mCRC pts with either single site (SS) or multiple sites (MS) according to LM status in the following treatment groups: A: chemotherapy (CT) alone, B: CT + VEGF-antibodies, C: CT + EGFR-antibodies in KRAS wild-type tumors, within first-line (1L) and second line (2L) of therapy and D: pts enrolled on third line (≥3L) trials treated with trifluridine/tipiracil or regorafenib and placebo. The primary and secondary endpoints were overall survival (OS) and progression-free survival (PFS) which were assessed using Kaplan-Meier estimates and adjusted Cox models on ECOG PS, age, and gender. Results: We included 26 trials with 17924 pts. 14066 pts had LM. Pts with LM had a higher rate of colon vs rectum as primary tumor (72 vs 62%; P < .001) and less SS (31 vs 47%; P < .001) than those with NLM. OS and PFS results in subgroups are reported in the table. In groups A and B, we found better OS and PFS outcomes in NLM pts as either SS or MS in 1L and 2L. In group C from 1L, we found better survival outcomes in pts with SS LM. In pts with MS, NLM superiority was observed in OS but not in PFS. However, these results were influenced by primary tumor sidedness. In group D, better OS and PFS was observed in pts without LM than those with LM whether in pts with SS or MS. Response rates were higher in LM than in NLM in most 1L and 2L subgroups. Conclusions: LM is a poor prognostic factor for mCRC increasing from the 1L to ≥3L. Survival with CT alone and CT + anti-VEGF according to LM and NLM differs significantly in 1L and 2L but not with CT + anti-EGFR. This data justifies using LM as a stratification factor at least in ≥3L trials. [Table: see text]