Use of KRAS codon 13 mutations to predict response to neoadjuvant chemoradiation therapy in patients with rectal adenocarcinoma.

453 Background: The predictive role of KRAS mutation in therapeutic management of metastatic colorectal cancer has been much investigated. However, the association between KRAS mutations and rectal cancer response to neoadjuvant chemoradiation therapy (CRT) remains unclear. Our objectives were to determine the incidence of KRAS mutations in patients with rectal cancer and identify potential correlations with response to CRT. Methods: Patients with Stage II-III rectal cancer (n=148) from a multicenter prospective clinical trial were assessed. DNA was extracted from pretreatment tumor biopsies; and genotyping of KRAS was completed by PCR and direct sequencing. All patients underwent pre-operative CRT followed by surgery; and treatment response was evaluated by a pathologist. Surgical specimens without evidence of residual disease were deemed to have a pathologic complete response (pCR). Results: Overall, 60 of 148 (40.5%) patients had KRAS mutation. Breakdown of the different KRAS mutations revealed that 40...