Is there any difference in overall response rate according to kras mutation in advanced colorectal cancer (aCRC)?

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e14589 Background: Tejpar et al (JCO2012; 30(29):3570-7) showed that patients with aCRC and Gly13D kras mutation experienced worse response rate with chemotherapy alone compared to those with other kras mutations. This retrospective study analyzes differences in clinical and radiological response between patients with the two main kras mutations: Gly12Val or Gly13D. Methods: In this retrospective-observational trial, patients with aCRC and Gly12Val and Gly13D kras mutation tumours participated. Clinical and radiological responses of patients with each of the two kras mutation, detected by Therascreen technique and treated with conventional first-line chemotherapy schemes, were recorded. SPSSv17 was employed. ORR (Overall Response Rate: CR+PR) and OCR (Overall Control Rate: CR+PR+SD) were calculated. Results: From November 2005 to October 2012, 51 patients with aCRC and Gly12Val or Gly13D kras mutations were included. Median age was 66 (41-80); 52.7 % men and 49.1% with synchronous disease. Kras mutation status was: 47.3% Gly13D and 52.7% Gly12Val. The chemotherapy schedules were based on Oxaliplatin, Irinotecan and others (61.5%, 25% and 13.5% respectively). While ORR was observed in 39.22 % (38.46 % Gly12Val and 40% Gly13D; p: 0.57), OCR was 76.5% (76.9% Gly12Val and 76% Gly13D; p: 0.60). In the Kaplan-Meier analysis, OS showed no difference between both kras mutation groups (Gly12Val: 29 months; Gly13D: 28 months; p: 0.28). Conclusions: According to our results, and in contrast to other studies outcomes, there is no difference regarding ORR, OCR or OS in patients with both different kras mutation: Gly12Val or Gly13D; however, the hypothetical role of Gly13D mutation as a biomarker of chemotherapy resistance, should be evaluated in prospective studies.