1Study A: phase 1/2 dose escalation study with 10% dose increment, in 18 fractions for 6 weeks. Study B: phase 1/2 dose escalation study with 10% dose increment in 16 fractions in 4 weeks. Data from both studies refers to a wider group of head and neck patients. RBE: relative biologic effectiveness, CNS: central nervous system, BID: bis in die, R0: negative resection margins, R+: positive resection margin, Bx: biopsy, na: not available.