AIM:To investigate the prognostic value of KRAS mutation,and phosphatase and tensin (PTEN) expression in Chinese metastatic colorectal cancer metastatic colorectal cancer (mCRC) patients treated with cetuximab.METHODS:Ninety Chinese mCRC patients treated with cetuximab were evaluated for KRAS mutation and PTEN protein expression by DNA sequencing of codons 12 and 13 and immunohistochemistry,respectively.We then selected 61 patients treated with cetuximab,either in combination with chemotherapy,or alone as a second-line or third-line regimen to assess whether KRAS mutation or PTEN protein expression is associated with the response and the survival time of mCRC patients treated with cetuximab.RESULTS:KRAS mutation was found in 30 (33.3%) tumor samples from the 90 patients,and positive PTEN expression was detected in 58 (64.4%) of the 90 patients.Among the 61 patients who were treated with cetuximab as a second-line or third-line regimen,the resistance to cetuximab was found in 22 patients with KRAS mutation and in 39 patients without KRAS mutation,with a response rate of 4.5% and 46.1% respectively (P=0.001),a shorter median progression-free survival (PFS) time of 14 ± 1.3 wk and 32 ± 2.5 wk respectively (P < 0.001),a median overall survival (OS) time of 11 ± 1.2 mo and 19 ± 1.8 mo respectively (P < 0.001),as well as in 24 patients with negative PTEN expression and in 37 patients with positive PTEN expression respectively (P < 0.001),with a responsive rate of 4.2% and 48.6% respectively,a shorter median PFS survival time of 17 ± 2.0 wk and 28 ± 1.9 wk respectively (P=0.07),and a median OS time of 11 ± 1.3 mo and 18 ± 1.9 mo respectively (P=0.004).Combined KRAS mutation and PTEN expression analysis showed that the PFS and OS time of patients with two favorable prognostic factors were longer than those of patients with one favorable prognostic factor or no favorable prognostic factor (P < 0.001).CONCLUSION:KRAS mutation and PTEN protein expression are significantly correlated with the response rate and survival time of Chinese mCRC patients treated with cetuximab. AIM: To investigate the prognostic value of KRAS mutation, and phosphatase and tensin (PTEN) expression in Chinese metastatic colorectal cancer metastatic colorectal cancer (mCRC) patients treated with cetuximab.METHODS:Ninety Chinese mCRC patients treated with cetuximab evaluated for KRAS mutation and PTEN protein expression by DNA sequencing of codons 12 and 13 and immunohistochemistry,respectively.We then selected 61 patients treated with cetuximab,either in combination with chemotherapy,or alone as a second-line or third-line regimen to assess whether KRAS mutation or PTEN Protein expression is associated with the response and the survival time of mCRC patients treated with cetuximab.RESULTS:KRAS mutation was found in 30 (33.3%) tumor samples from the 90 patients, and positive PTEN expression was detected in 58 (64.4%) of The 90 patients.Among the 61 patients who were treated with cetuximab as a second-line or third-line regimen,the resistance to cetuximab was found in 22 patient In patients with KRAS mutation and in 39 patients without KRAS mutation, with a response rate of 4.5% and 46.1% respectively (P = 0.001), a extraordinary median progression-free survival (PFS) time of 14 ± 1.3 wk and 32 ± 2.5 wk Respectively (P < 0.001), a median overall survival (OS) time of 11 ± 1.2 mo and 19 ± 1.8 mo respectively (P < 0.001), as well as in patients with negative PTEN expression and in 37 patients with positive PTEN expression Respectively (P < 0.001), with a responsive rate of 4.2% and 48.6% respectively, a short median PFS survival time of 17 ± 2.0 weeks and 28 ± 1.9 weeks (P = 0.07), and a median OS time of 11 ± 1.3 mo and 18 ± 1.9 mo respectively (P=0.004). Combined KRAS mutation and PTEN expression analysis analysis that that PFS and OS time of patients with two favorable prognostic factors were longer than those of patients with one favorable prognostic factor or no favorable prognostic Factor (P < 0.001).CONCLUSION:KRAS mutation and PTEN protein expression are significan Tly corrElated with the response rate and survival time of Chinese mCRC patients treated with cetuximab.