Brian C Netzel1, Stefan K G Grebe. 1. Department of Laboratory Medicine and Pathology Mayo Clinic, Hilton 7, 200 1st Street SW, Rochester, MN 55905, USA.
Abstract
BACKGROUND: KRAS codons 12 and 13 mutations are commonly used to identify colorectal carcinoma (CRC) patients who are unlikely to benefit from anti-EGFR therapy. However, humans have four different homologous RAS proteins and no routine screening is performed for the other mutation sites. Non-screened mutations may still be present in a significant subset of patients without KRAS codon 12 and 13 mutations. METHODS: We developed a LightCycler screening assay that encompasses codons 12, 13 and 61 of all RAS genes. Screen-positive specimens were characterized by Sanger sequencing. 130 CRC specimens were screened for all RAS genes. The results for KRAS codons 12 and 13 were compared with an FDA approved method (Qiagen). RESULTS: Twenty-nine of 130 specimens (22.3%) were positive for KRAS codons 12 and 13, with 100% congruence with the Qiagen method. Six additional specimens were identified to have mutations. One mutation in HRAS codon 61, two in KRAS codon 61, and three in NRAS codon 61. CONCLUSION: Limiting RAS testing to only KRAS codons 12 and 13 in companion diagnostic testing of CRC results in nearly 1/5 of patients with RAS mutations not being excluded from costly EGFR antagonist treatment, despite likely futility. Inclusion of all RAS genes in companion diagnostic screening is warranted.
BACKGROUND:KRAS codons 12 and 13 mutations are commonly used to identify colorectal carcinoma (CRC) patients who are unlikely to benefit from anti-EGFR therapy. However, humans have four different homologous RAS proteins and no routine screening is performed for the other mutation sites. Non-screened mutations may still be present in a significant subset of patients without KRAS codon 12 and 13 mutations. METHODS: We developed a LightCycler screening assay that encompasses codons 12, 13 and 61 of all RAS genes. Screen-positive specimens were characterized by Sanger sequencing. 130 CRC specimens were screened for all RAS genes. The results for KRAS codons 12 and 13 were compared with an FDA approved method (Qiagen). RESULTS: Twenty-nine of 130 specimens (22.3%) were positive for KRAS codons 12 and 13, with 100% congruence with the Qiagen method. Six additional specimens were identified to have mutations. One mutation in HRAS codon 61, two in KRAS codon 61, and three in NRAS codon 61. CONCLUSION: Limiting RAS testing to only KRAS codons 12 and 13 in companion diagnostic testing of CRC results in nearly 1/5 of patients with RAS mutations not being excluded from costly EGFR antagonist treatment, despite likely futility. Inclusion of all RAS genes in companion diagnostic screening is warranted.
Authors: Kristoffer Watten Brudvik; Yoshihiro Mise; Michael Hsiang Chung; Yun Shin Chun; Scott E Kopetz; Guillaume Passot; Claudius Conrad; Dipen M Maru; Thomas A Aloia; Jean-Nicolas Vauthey Journal: Ann Surg Oncol Date: 2016-03-25 Impact factor: 5.344
Authors: Crescent R Isham; Brian C Netzel; Ayoko R Bossou; Dragana Milosevic; Kendall W Cradic; Stefan K Grebe; Keith C Bible Journal: J Clin Endocrinol Metab Date: 2014-03-14 Impact factor: 5.958
Authors: Yu Imamura; Paul Lochhead; Mai Yamauchi; Aya Kuchiba; Zhi Rong Qian; Xiaoyun Liao; Reiko Nishihara; Seungyoun Jung; Kana Wu; Katsuhiko Nosho; Yaoyu E Wang; Shouyong Peng; Adam J Bass; Kevin M Haigis; Jeffrey A Meyerhardt; Andrew T Chan; Charles S Fuchs; Shuji Ogino Journal: Mol Cancer Date: 2014-05-31 Impact factor: 27.401