Endorectal Brachytherapy Boost After External Beam Radiation Therapy in Elderly or Medically Inoperable Patients With Rectal Cancer : Primary Outcomes of the Phase 1 HERBERT Study

Purpose To evaluate the toxicity and efficacy of the combination of external beam radiation therapy (EBRT) followed by high-dose-rate endorectal brachytherapy (HDREBT) boost in elderly and medically inoperable patients with rectal cancer. Methods and Materials A phase 1 dose-escalation study was performed. Treatment consisted of EBRT (13 × 3 Gy) followed by 3 weekly brachytherapy applications 6 weeks later. The HDREBT dose started at 5 Gy per fraction, increasing with 1 Gy per fraction if dose-limiting toxicity (DLT, defined as grade ≥3 proctitis