- Patients must have a documented FGFR2 activating mutation either on primary, recurrent or metastatic biopsy. Over 90% of FGFR2 mutations occur at 7 codons. Activating mutations are defined as the known FGFR2 hotspots at S252W, P253R, S373C, Y376C, C383R, N550K, N550H, K660E.