Open Access
ARTICLE
Differential Tumor Response and Conversion Outcomes Associated with First-Line Biologic Strategies in Liver-Limited RAS Wild-Type Metastatic Colorectal Cancer
Shih-Wei Chiang1,2, Ming-Cheng Chen2,3, Chang-Lin Lin2, Yi-Lin Huang2, Feng-Fan Chiang2,4,*, Shun-Fa Yang1,5,*
1 Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan
2 Division of Colorectal Cancer, Department of Surgery, Taichung Veterans General Hospital, Taichung, Taiwan
3 School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
4 College of Humanities and Social Sciences, Providence University, Taichung, Taiwan
5 Department of Medical Research, Chung Shan Medical University Hospital, Taichung, Taiwan
* Corresponding Author: Feng-Fan Chiang. Email: 
; Shun-Fa Yang. Email: 
(This article belongs to the Special Issue: RAS Driven Oncogenesis and the Future of Combination Therapy in Solid Tumors)
Oncology Research https://doi.org/10.32604/or.2026.085229
Received 07 May 2026; Accepted 14 July 2026; Published online 30 July 2026
Abstract
Background: Anti-EGFR therapy is widely used as first-line treatment for RAS wild-type metastatic colorectal cancer (mCRC), particularly in patients with left-sided tumors. In liver-limited disease, maximizing tumor shrinkage may facilitate conversion to resectability; however, comparative real-world evidence among panitumumab, cetuximab, and bevacizumab remains limited. This study aimed to compare the clinical outcomes of these biologic agents in patients with RAS wild-type mCRC. Methods: We retrospectively analyzed 241 patients with RAS wild-type mCRC treated with first-line chemotherapy plus panitumumab (n = 76), cetuximab (n = 80), or bevacizumab (n = 85) between 2016 and 2024. Outcomes included depth of response (DpR), objective response rate (ORR), disease control rate (DCR), conversion surgery rate, progression-free survival (PFS), and overall survival (OS). Results: Overall, panitumumab demonstrated superior tumor response, achieving the highest ORR (69.7%) and conversion surgery rate (34.2%), although PFS and OS were comparable among treatment groups. In patients with liver-limited disease, panitumumab was associated with a higher conversion surgery rate than bevacizumab (50.0% vs. 19.4%) and a trend toward longer OS. Right-sided primary tumors and BRAF mutation remained independent predictors of poorer OS. Conclusions: Panitumumab-based therapy was associated with deeper tumor shrinkage and higher conversion rates, particularly in liver-limited mCRC. These findings suggest that greater cytoreduction may increase opportunities for local treatment in selected patients. However, given the retrospective nature of the study, the findings should be considered hypothesis-generating and require prospective validation.
Keywords
Metastatic colorectal cancer; RAS wild-type; panitumumab; cetuximab; bevacizumab; conversion surgery
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