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ABSTRACT Background Over the years, prognostic indexes have been developed to help clinicians stratify patients with biliary tract cancers (BTC) into risk groups. This study aims to identify a new prognostic index for patients with BTC treated with cisplatin, gemcitabine and durvalumab (CGD) in the first‐line setting. Patients and Methods The study population consisted of patients with BTC from 11 Eastern and Western Countries. Using multivariate analysis for overall survival (OS), we identified 5 baseline statistically significant variables: stage, carcinoembryonic antigen (CEA) levels, albumin levels, gamma glutamyl transferase (GGT) levels, neutrophil‐to‐lymphocyte ratio (NLR). Metastatic disease is a prognostic factor with a superior weight considering the HR of 3.62, while all the others can be considered prognostic factors with equivalent weight as the HRs are quite similar (HRs between 1.55 and 1.92). Based on these reasons, we developed a prognostic model called the MAGIC‐D index by assigning a score of 2 for metastatic disease, and a score of 1 for CEA increased levels, albumin decreased levels, GGT increased levels, NLR ≥ 3. Patients were stratified into three risk groups as follows: low‐risk group (Score from 0 to 2), intermediate‐risk group (Score from 3 to 4) and high‐risk group (Score from 5 to 6). At the first data cutoff (April 2024), these data were available for 319 patients that composed the training cohort used for the analysis. At the second data cutoff (May 2025), 79 patients were further enrolled and composed the validation cohort. Results Median progression‐free survival was 11.7 months in low‐risk group (20.7%), 8.7 months in intermediate‐risk group (46.4%) and 5.4 months in high‐risk group (32.9%) [low‐risk hazard ratio (HR): 0.27, intermediate‐risk HR: 0.55, high‐risk HR: 1, p < 0.0001]. Median OS was 18.4 months in low‐risk group,15.9 months in intermediate‐risk group and 7.8 months in high‐risk group (low‐risk HR: 0.17, intermediate‐risk HR: 0.43, high‐risk HR: 1, p < 0.0001). There was no difference in overall response rate (low‐risk: 31.8%, intermediate‐risk: 36.5% and high‐risk: 25.7%; p = 0.0718), while disease control rate was significantly different across the three risk groups (low‐risk: 83.3%, intermediate‐risk: 70.9% and high‐risk: 60.9%; p < 0.0001) as well as the rate of patients receiving a second‐line therapy (low‐risk: 54.5%, intermediate‐risk: 48.6% and high‐risk: 25.7%; p = 0.0061). Finally, the prognostic role in terms of OS and PFS of the MAGIC‐D index was confirmed in a validation cohort of 79 patients. Conclusion The MAGIC‐D index is an easy‐to‐use tool able to stratify patients with BTC with different prognoses undergoing first‐line therapy with CGD.

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.

3569 Background: Immune checkpoint inhibitors (ICIs) are a standard treatment for gastrointestinal (GI) cancers with mismatch repair deficiency (dMMR) or microsatellite instability (MSI). However, around 50% of patients develop resistance to ICIs, during treatment or after discontinuation. In these patients, the efficacy of reuse an ICI in patients progressing during a previous ICI (rechallenge), or in patients who progressed after discontinuation (reintroduction), remains unknown. The INFLATE study evaluates the efficacy of ICI reuse in patients who progressed on or after discontinuing ICI. Methods: This is a multicenter international retrospective study from the IMMUNODIG cohort, including patients from 34 centers in France, the United States, Italy, Belgium and Spain. All patients received ICI for dMMR/MSI GI cancer. We analyzed patients who had progressed following initial ICI (ICI-1) and subsequently received a rechallenge or a reintroduction with ICI (ICI-2), either monotherapy (mono-ICI) or biotherapy (bi-ICI). Results: A total of 77 patients were included, receiving bi-ICI (N = 34) or mono-ICI (N = 43) during ICI-2. The majority (76%) had a metastatic colorectal cancer. The reason for discontinuing ICI-1 was disease progression in 53% of cases, end of treatment in 15%, toxicity in 5% and other reasons in 26%. Patients who discontinued ICI-1 due to progression received MONO-ICI-2 in 29% of cases and BI-ICI-2 in 71%, whereas those who stopped for other reasons received MONO-ICI-2 in 86% and BI-ICI-2 in 14% of cases. Efficacy results are shown in Table 1. The ORR and DCR were 26% and 79% with MONO-ICI-2, and 16% and 71% with BI-ICI-2. Among patients who discontinued ICI-1 due to progression, BI-ICI-2 (N = 29) achieved an ORR and DCR of 8% and 65%, with a median PFS of 5.5 months (95%CI 4.07-10.4). These outcomes were 17%, 67%, and 3.7 months (95%CI 2.37-NA), respectively, with MONO-ICI-2 (N = 12). For patients who discontinued ICI-1 for reasons other than progression, BI-ICI-2 (N = 5) achieved an ORR and DCR of 60% and 100%, with a median PFS not reached (95%CI 11.5-NR), while MONO-ICI-2 (N = 31) achieved 29%, 82%, and 14.2 months (95%CI 11.2–NR), respectively. Conclusions: This is the first multicenter real-world study evaluating ICI reuse in dMMR/MSI GI cancers. In patients who discontinued ICI for reasons other than progression, reintroduction of ICI therapy upon progression achieves tumor control in 85% of cases. In cases of progression on mono-ICI, Bi-ICI re-challenge achieve tumor control in two-thirds of cases and might be to consider in some patients. ORR % DCR % PFS median (95%CI) OS median (95%CI) Overall N=77 21 76 7.65 months(5.5–11.5) 27.6 months(22.2–55.7) Discontinued ICI-1 due to Progression N=41 11 68 5.03 months(3.7–8.05) 26.7 months(21.1–NR) Discontinued ICI-1 for Other Reasons N=36 33 85 14.22 months(11.24–NR) 27.6 months(22.2–NR)

AbstractStandard of care first‐line systemic treatment for advanced biliary tract cancer includes chemo‐immunotherapy with gemcitabine, cisplatin, and durvalumab, followed by maintenance durvalumab monotherapy. The present work aims to investigate the differences in baseline clinical and molecular characteristics between patients with early progression during chemo‐immunotherapy and those who reach durvalumab maintenance therapy. The study population included patients with unresectable, locally advanced, or metastatic BTC who received treatment at 38 clinical Institutions in 12 countries from July 2021 to December 2023. The primary objective of the study was to investigate whether baseline clinical and molecular characteristics differed between patients with early progression during chemo‐immunotherapy versus those reaching durvalumab maintenance therapy. Four hundred forty‐eight patients were included in this study. Two hundred twenty‐seven patients (50.7%) received maintenance with durvalumab monotherapy, whereas 221 (49.3%) did not receive maintenance therapy due to PD during first‐line chemo‐immunotherapy before completing 8 cycles. Results show that patients who received maintenance were more likely to be older (≥70 years), have an ECOG = 0, locally advanced disease, and a neutrophil‐to‐lymphocyte ratio (NLR) <3. A higher proportion of patients with BAP1 mutations received maintenance, while TP53 mutations were more common in those who progressed early. According to the present analysis, a substantial proportion of patients (50.7%) with advanced BTC who were treated with chemotherapy plus durvalumab proceeded to receive maintenance therapy with durvalumab monotherapy, with a median treatment duration of 4.4 cycles. Patients ≥70 years, with ECOG PS 0, with locally advanced disease, and with NLR <3 had a higher likelihood of receiving maintenance therapy.

142 Background: Fruquintinib (F) is a highly selective, oral tyrosine kinase inhibitor of all 3 vascular endothelial growth factor receptors (VEGFRs -1, -2, -3) that is approved by the US FDA and in the EU, UK, and Japan for previously treated metastatic colorectal cancer (mCRC), regardless of biomarker status. FRESCO-2 (NCT04322539) met its primary endpoint demonstrating significantly improved overall survival (OS) with F + best supportive care (BSC) vs placebo (P) + BSC. This subgroup analysis assessed landmark survival of all FRESCO-2 patients (pts), and baseline (BL) characteristics and safety data of pts treated with F who had OS ≥10 months (mos) compared with the intent-to-treat (ITT) population (pop). Methods: Pts were randomized 2:1 to receive F 5 mg or matching P, by mouth, once daily, 3 weeks on, 1 week off, + BSC. Pts had received prior chemotherapy, anti-VEGF therapy and, if RAS wild type, anti-EGFR therapy; and had prior exposure to trifluridine/tipiracil (TAS-102) and/or regorafenib. The hazard ratio (HR) between the two treatment arms was calculated from a stratified Cox proportional hazard model with treatment group as the only covariate in the model. Results: In the ITT pop, OS was improved with F vs P (HR 0.66); OS rates (95% confidence intervals [CIs]) at 6 and 9 mos were 60.4% (55.9–64.9) vs 41.5% (35.0–48.0) and 41.1% (36.4–45.8) vs 28.2% (22.1–34.3), respectively. Progression-free survival (PFS) rates (95% CIs) at 6 and 9 mos were 23.8% (19.7–28.0) vs 1.1% (0–2.6) and 11.3% (8.1–14.6) vs 0.5% (0–1.6), respectively. Of 461 pts who received F, 113 (24.5%) had OS ≥10 mos (range 10.0–18.9) with a median duration of F treatment of 6.3 mos (range 0.7–19.1). Among pts receiving F, a higher proportion (≥10% difference) of pts with OS ≥10 mos had no liver metastases (mets) and an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 at BL compared with the ITT pop (Table). In pts with OS ≥10 mos, 61.9% experienced a grade ≥3 treatment-emergent adverse event compared with 62.7% in the ITT pop. Conclusions: Longer-term OS and PFS rates at 6 and 9 mos were higher with F vs P in the FRESCO-2 ITT pop. The data show a higher proportion of pts with OS ≥10 mos had an absence of liver mets and ECOG PS 0 at BL than the ITT pop. The safety profile of F in pts with OS ≥10 mos was consistent with the ITT pop. Clinical trial information: NCT04322539 . BL characteristics of pts treated with F with OS ≥10 mos vs ITT pop. BL characteristic Pts with OS ≥10 mos (n=113) ITT pop(n=461) ECOG PS (0 / 1), % 54.0 / 46.0 42.5 / 57.5 Median time since 1 st CRC diagnosis, mos 52.0 47.2 Primary tumor location at 1 st diagnosis (colon / rectum / both), % 51.3 / 35.4 / 13.3 60.5 / 31.0 / 8.5 Primary site at 1 st diagnosis (colon left / colon right), % 42.5 / 15.9 41.6 / 21.0 Liver mets, % 58.4 73.5 Median duration of mCRC, mos 42.7 37.9 Prior lines of therapy for mCRC (≤3 / >3), % 26.5 / 73.5 27.1 / 72.9 Prior TAS-102, % 46.9 52.1 Prior regorafenib, % 12.4 8.7

Background Immune checkpoint inhibitors (ICIs) are recommended to treat patients with deficient mismatch repair/microsatellite instability high (dMMR/MSI-H) metastatic colorectal cancer (mCRC). Pivotal trials have fixed a maximum ICI duration of 2 years, without a compelling rationale. A shorter treatment duration has the potential to improve patients' quality of life and reduce both toxicity and cost without compromising efficacy. Here we examine whether early treatment discontinuation (ETD) before 13 months in patients without progressive disease (PD) can lead to similar long-term disease control compared with a longer treatment duration (LTD). Methods To assess whether ETD is associated with similar outcomes compared with LTD, we assembled an international cohort of patients with dMMR/MSI-H mCRC treated with ICIs who stopped treatment for a reason other than PD within 395 days (ETD group) and compared them to those who continued for >395 days (LTD group). Outcomes were adjusted for patient/tumor characteristics. Primary endpoint was progression-free survival (PFS) and secondary endpoints were objective response rate (ORR), overall survival (OS) and safety. Results Of 976 patients, 137 and 394 were allocated to the ETD and LTD groups, respectively. In the ETD group, treatment was discontinued due to toxicity (n=56), objective response (n=43), surgery (n=28), patient decision (n=2) or other reasons (n=8). Baseline characteristics were well balanced between the two groups: 22% in both groups received both anti-programmed death-(ligand) 1 (anti-PD-(L)1) + anti-cytotoxic T-lymphocyte antigen-4 (anti-CTLA-4); all others received anti-PD-(L)1 monotherapy. ORR to ICIs was 81% in both groups. Median duration of treatment was ~7 months in the ETD and ~24 months in the LTD group. After a median follow-up of 44 months (IQR: 30–67), similar PFS (HR: 0.92, 95% CI: 0.60 to 1.40, p=0.69) and OS (HR: 1.15, 95% CI: 0.66 to 1.99, p=0.62) from the start of ICIs were observed in ETD and LTD patients. In the ETD group, 28 (20%) patients had a PFS event and 9 restarted ICIs with a disease control rate of 66%. Conclusions In our international series of dMMR/MSI-H mCRC, ETD of ICIs in the absence of PD did not seem detrimental in terms of PFS and OS compared with continuing treatment beyond 1 year. Randomized clinical trials to compare short and long treatment duration are now warranted.

Abstract Background In the TOPAZ-1, patients with biliary tract cancers (BTC) and recurrence within 6 months after surgery were excluded, even if this event is frequently observed in clinical practice. Our study aimed to assess if the efficacy of cisplatin-gemcitabine-durvalumab (CGD) in this population is comparable to that reported in the phase 3 trial. Methods The study cohort included patients with BTC who underwent surgery on the primary tumor, experienced disease recurrence occurring ≤6 months or &gt;6 months after surgery or after the end of adjuvant therapy and started CGD. The primary objectives were overall survival (OS) and progression free survival (PFS). Results A total of 178 patients were enrolled. No significant differences were observed between early and late relapse groups in OS (23.4 months vs not reached; HR 1.26; 95% CI, 0.67-2.37; P = .45) and PFS [7.0 months vs 9.8 months; HR 1.3(95% CI, 0.9-2.1) P = .13]. Overall response rate and disease control rate (P = .33 and P = .62) were comparable between the 2 groups, as the overall safety profile. In addition, we compared survival outcomes between the selected population and a historical cohort of patients with BTC treated with cisplatin-gemcitabine (CG) and found that despite the absence of statistical significance, CGD showed an outcome trend compared with CG regardless of the time of recurrence after surgery or adjuvant chemotherapy [(CG ≤ 6 vs CGD ≤ 6 months: HR 0.59, 95%CI, 0.35-1.01, P = .05; HR 0.70; 95%CI, 0.46-1.06, P = .09, OS and PFS, respectively) and (CG &gt; 6 vs. CGD &gt; 6 months: HR 0.50; 95%CI, 0.29-0.88, P = 0.0165; HR 0.54; 95%CI, 0.35-0.84, P = .0068, OS and PFS, respectively)]. Conclusion Our analysis suggests that CGD retains its efficacy independently of the timing of relapse after surgery or completion of adjuvant treatment in patients with advanced BTC.

PURPOSE The adjuvant treatment for stage III colon cancer (CC) is chemotherapy combining fluoropyrimidine (FP) and oxaliplatin (OX). FP regimen plus OX (FPOX) may benefit in high-risk stage II CC. We performed a pooled analysis of pivotal MOSAIC and C-07 studies evaluating FPOX for the treatment of high-risk stage II CC according to prognostic factors, number of high-risk factors, and current clinicopathologic risk classification on the basis of T stage, tumor perforation, and number of lymph nodes examined. PATIENTS AND METHODS One thousand five hundred and ninety-five patients with stage II CC receiving FP or FPOX were pooled. The overall survival (OS) benefit of OX was analyzed using Kaplan-Meier curves and unadjusted Cox models stratified by study. Three thousand and fifty-nine patients with stage III CC were used only for interaction tests between the allocated chemotherapy and stage. RESULTS In the pooled analysis of stage II patients, independent prognostic factors in multivariable analysis were sex, age, perforation/obstruction, and tumor sidedness. There was a significant interaction in OS between stage and allocated chemotherapy with hazard ratios (HRs) of 1.03 for stage II (95% CI, 0.82 to 1.29; P = .813) and 0.82 for stage III (95% CI, 0.73 to 0.92; P = .001; P int = .073). There was no benefit from the addition of OX to FP for any of the prognostic factors. The number of high-risk factors tested was not predictive of OX benefit. According to the currently agreed clinicopathologic risk classification, no OS benefit of OX was observed, as HR was 0.86 (95% CI, 0.63 to 1.18; P = .349). CONCLUSION No OS benefit of adjuvant OX was found in high-risk stage II CC, regardless of the definition used to characterize tumors as having a high risk for recurrence. Hence, our analysis suggests that OX should not be the standard of care for adjuvant chemotherapy for stage II CC, even in high-risk patients.

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]