Primary Tumor Location and RAS/BRAF Mutational Status as Prognostic Factor in Stage III Colon Cancer

To the Editor The post hoc analysis from the PETACC-8 trial reported by Taieb et al showed that the association between primary tumor location cancer and disease-free survival in patients with stage III colon cancer varied on the basis of RAS and BRAF molecular status. In particular, while patients with RAS/BRAF wild-type right-sided tumors had a worse prognosis, patients with RAS- or BRAF-mutant right-sided tumors had a significantly better disease-free survival in comparison with those with left-sided tumors, which is just the opposite of what we observed in the metastatic setting. No possible explanations have been proposed by the authors because neither association between sidedness and disease-free survival according to microsatellite instability status, nor predictive effect of tumor location for cetuximab efficacy, was found.

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