Correlation Between EGFR Expression And KRAS Genetype With Tumor Regression Of Rectal Cancer After Preoperative Chemoradiotherapy

Objective To evaluate whether the protein expression of EGFR and the presence of KRASgene mutations are useful tumor-response marker in patients with locally advanced rectalcancer treated with preoperative chemoradiotherapy. Methods43patients with locallyadvanced rectal cancer who were treated with preoperative chemoradiotherapy were enrolled.Using immunohistochemical SP method to detected the expression of EGFR protein from patientsbefore and after chemoradiotherapy. DNA was isolated from paraffin-embedded tissues beforechemoradiotherapy amplified by PCR, and then sequenced in order to detect KRAS mutationsin codons12﹑13. Post-operative specimens were classified according to the Dwork’s tumorregression grading (TRG). Good tumor regression was defined as TRG2+3+4，insignificanttumor regression as TRG0+1. Results1.29(67.4%）patients were graded as TRG2+3+4,14（32.6%）as TRG0+1in43patients, including two patients(4.7%) who have pathologiccomplete regression (pCR).2.The Expression rates of EGFR protein in TRG(2+3+4) groupand TRG(0+1) group were37.9%and71.4%, respectively, the difference was statisticmeaning among the two grous (P﹤0.05);3.The expression rates of EGFR protein in patientsbefore and after chemoradiotherapy were51.2%and65.8%, respectively, the differences hadno statistical significance(P﹥0.05);4.DNA was extracted from43patients, KRAS mutationoccured in15patients (34.9%), of which mutation in codon12occurred in11patients(73.3%),and mutation in, codon13occurred in4patients (26.7%).29(67.4%）patients were graded asTRG2+3+4,14（32.6%）as TRG0+1. Pathologic response rates in KRAS gene mutationgroup and wild group were66.7%and67.8%, respectively, with no significant differencebetween two groups (P>0.05).5.The differences of between the expression of EGFR protein and KRAS gene types between different rectal cancer patients’ sex，ages, differentiations,clinical stages and lymphnode metastasis had nostatistical significance(P>0.05).Conclusions1.There is significant difference in the expressions of EGFR protein beforepreoperative chemoradiotherapy for rectal cancer in the different tumor regression groups, theexpressions of EGFR protein can predict response to preoperative chemoradiotherapy.2.Nosignificant change in the expressions of EGFR protein before and after chemoradiotherapy.3.There is no difference in the degree of tumor pathological regression after preoperativechemoradiotherapy for rectal cancer in the different KRAS genotypes, KRAS mutation statusdoes not predict response to preoperative chemoradiotherapy.4.The expression of EGFRprotein and KRAS gene types had no correlation with patients’sex, ages, differentiations,clinical stages and lymphnode metastasis.