P-320 - The role of the status for KRAS mutation as a biomarker in only metastatic rectal cancer

Date 04 July 2015
Event WorldGI 2015
Session Posters
Topics Biomarkers
Rectal Cancer
Presenter S. Byeon
Citation Annals of Oncology (2015) 26 (suppl_4): 1-100. 10.1093/annonc/mdv233
Authors S. Byeon1, S.T. Kim1, J. Lee1, J.O. Park2, H.Y. Lim1, W.K. Kang1, S.H. Park1, S.J. Lee1, Y.S. Park1
  • 1Samsung Medical Center, Seoul/KR
  • 2Sungkyunkwan University School of Medicine, Seoul/KR

Abstract

Introduction

The adding of anti- Epidermal growth factor receptor (EGFR) monoclonal antibody in metastatic colorectal cancer (mCRC) with KRAS wild type has improved the treatment outcomes. But only few studies had evaluated the role of KRAS mutation status and adding anti-EGFR therapies for only metastatic rectal cancer.

Methods

We reviewed the medical records of all patients with mCRC in Samsung medical center from June 2005 to February 2015. Medical records contained the status of KRAS mutation and anti-cancer therapies including anti-EGFR therapies. We investigated to analyze the role of KRAS as a biomarker in metastatic rectal cancer patients.

Results

Total 1007 patients who identified KRAS status and received standard systemic chemotherapy for mCRC were reviewed. Of all 1007 patients, 174 patients were identified in metastatic rectal cancer patients. There were 109 males and 65 females, and mean age was 58 years. A most common metastatic site was liver. 127 patients identified had the wild type KRAS, and 47 patients had the mutant KRAS. Patients with mutant type KRAS had longer OS (49.6 months vs 37.0 months, p = 0.031) than wild type KRAS. In subgroup analysis of patients with wild type KRAS (N = 127), 42 patients had received the anti-EGFR therapy (cetuximab). These 42 patients showed better PFS (15.5 vs 6.8, p = 0.003) than KRAS wild type patients without the anti-EGFR therapy (cetuximab). However, there was no statistically difference for OS.

Conclusion

The status of KRAS mutation may have the role of prognostic biomarker in metastatic rectal cancer patients. In patients with only KRAS wild type, adding the anti-EGFR agent is useful to prolong the PFS, Not OS.