Abstract 6408: Early carcinoembryonic antigen (CEA) dynamics to predict the efficacy of fruquintinib (F) + best supportive care (BSC) in patients with metastatic colorectal cancer (mCRC) enrolled in FRESCO-2

Abstract Background: The phase 3 FRESCO-2 trial (NCT04322539) demonstrated a significant survival benefit with fruquintinib (F) + BSC vs placebo (P) + BSC as third or later line of therapy for patients (pts) with mCRC. Based on the results of FRESCO-2, F was FDA-approved for adults with previously treated mCRC, irrespective of biomarker status. In mCRC, CEA levels and imaging are routinely used to monitor response to systemic therapy. We investigated early CEA changes during treatment in FRESCO-2 and possible relationships with efficacy. Methods: Pts with abnormal baseline (BL) CEA were included based on local lab reference ranges. Serum CEA levels were measured at BL and Day 1 (D1) of each 28-day cycle (C) except C1. Changes in CEA levels were analyzed at C2D1 and C3D1. CEA response was defined as ≥50% decrease from BL, and CEA progression was defined as ≥100% increase from BL. Tumor evaluation was performed by CT or MRI scan every 2 cycles. Overall survival (OS) and progression-free survival (PFS) were evaluated by Kaplan-Meier method; hazard ratio (HR) was estimated via Cox proportional hazards model; p-value was generated from log rank test. Results: Overall, 88.3% (407/461) vs 90.4% (208/230) of pts had abnormal BL CEA in F vs P arms; median BL CEA values were similar between treatment arms (Table). At C3D1, the proportion of pts who had a CEA response was significantly higher with F vs P (35.5% vs 3.8%, P <0.001) and the proportion who had CEA progression was significantly lower (5.7% vs 47.2%, P <0.001). Pts in the F arm with CEA response at C3D1 had improved OS and PFS vs pts without CEA response and pts with CEA progression (Table). These results were consistent for pts who had an early CEA response at C2D1 (Table). Conclusion: CEA response at C2D1 and C3D1 could be considered an early predictor for improved OS and PFS. Pts with CEA response seem to benefit from F + BSC compared with pts without response or with CEA progression. Table. CEA changes from baseline in pts in the F + BSC vs P + BSC arms, and OS and PFS based on CEA response in pts in the F + BSC arm CEA changes from baseline by treatment arm (ITT population) F + BSC (N=461) P + BSC (N=230) Baseline, n 407 208 Median CEA (range), µg/L 132.4 (3.0-213000.0) 169.6 (3.2-90010.0) C2D1, n 340 151 Median CEA (range), µg/L 93.3 (2.0-98660.0) 133.5 (2.7-255910.0) Median change from baseline (range), % -19.2 (-90.5-467.8) 44.2 (-61.7-606.8) C3D1, n 245 53 Median CEA (range), µg/L 78.3 (1.7-133390.0) 145.2 (3.9-17782.0) Median change from baseline (range), % -31.0 (-91.4-2195.8) 90.5 (-68.9-3776.6) OS and PFS for pts in the F + BSC arm with or without CEA response at C2D1 and C3D1 Pts with early CEA response at C2D1(n=66) Pts without early CEA response at C2D1 (n=274) Pts with CEA response at C3D1 (n=87) Pts without CEA response at C3D1 (n=158) Median OS, months 10.0 7.4 11.1 8.5 HR (95% CI), P value 0.62 (0.44-0.89), P = 0.009 0.65 (0.46-0.92), P = 0.015 Median PFS, months 5.6 3.7 5.8 4.2 HR (95% CI), P value 0.68 (0.51-0.92), P = 0.01 0.58 (0.44-0.78), P = 0.0003 OS and PFS for pts in the F + BSC arm with CEA response or CEA progression at C2D1 and C3D1 Pts with early CEA response at C2D1(n=66) Pts with early CEA progression at C2D1 (n=15) Pts with CEA response at C3D1 (n=87) Pts with CEA progression at C3D1 (n=14) Median OS, months 10.0 4.3 11.1 5.6 HR (95% CI), P value 0.27 (0.14-0.51), P <0.0001 0.23 (0.12-0.45), P <0.0001 Median PFS, months 5.6 1.9 5.8 3.4 HR (95% CI), P value 0.30 (0.16-0.56), P <0.0001 0.25 (0.13-0.48), P <0.0001 Citation Format: Sara Lonardi, Arvind Dasari, Rocio Garcia-Carbonero, Takayuki Yoshino, Pilar García-Alfonso, Judit Kocsis, Chiara Cremolini, François Ghiringhelli, Ardaman Shergill, Howard S Hochster, Michel Ducreux, Dirk Arnold, Varsha Sundaresan, Siddha Kasar, Adela Pina, Ziji Yu, William R Schelman, Lucy Chen, Josep Tabernero. Early carcinoembryonic antigen (CEA) dynamics to predict the efficacy of fruquintinib (F) + best supportive care (BSC) in patients with metastatic colorectal cancer (mCRC) enrolled in FRESCO-2 [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 6408.