In QUASAR 2, overall mutation burden and mutations in four specific genes (TP53, KRAS, BRAF, and GNAS) showed promising individual associations with relapse-free survival (predefined p<0·10) and were thus selected for multivariable analysis, together with T stage, N stage, treatment group (because bevacizumab had previously been associated with poor prognosis in our patient subgroup, although not the whole trial), and MSI (which co-varied with mutation burden and is probably the best established prognostic factor for colorectal cancer; table 1, appendix p 19). The gene discussed is BRAF; the disease is colorectal cancer.