602TiP - Re-RAD-I external beam radiotherapy for pelvic recurrences in rectal cancer patients previously treated with radiotherapy

Abstract

Background: Multimodal treatment of rectal cancer has improved outcome, but some patients still experience local recurrence, which is a major therapeutic challenge after previous radiotherapy (RT). Re-irradiation may improve the rate of radical surgery (R0), as reported in previous studies, where hyperfractionated chemo-RT resulted in 35% R0 rate. Surgery, RT techniques, and imaging have improved recent years, allowing for increased treatment precision with less morbidity. This study investigates re-irradiation of patients with local recurrence in a phase II clinical, imaging and translational study. Trial design: A prospective multicenter phase II, open label, non-randomised study. Therapy: External beam RT of 40.8 Gy / 1.2 F BID by intensity-modulated RT + CBCT guidance, concomitant capecitabine 825 mg/m2 BID all RT days, and surgery 8 weeks post-RT. The primary endpoint is R0 rate. Secondary objectives: Recurrence-free, disease-free and overall survival, acute and late toxicity, patient reported outcomes, translational research, imaging studies for future adaptive RT, mapping of recurrences according to previous RT, and simulation studies of other RT modalities (proton therapy). Main inclusion criteria: Locally recurrent rectal cancer, previous pelvic RT and surgery, potentially resectable tumor, age ≥18 years, adequate organ function, acceptable bowel and bladder function, acceptance for translational research. Main exclusion criteria; central small recurrences deemed resectable, non-resectable distant metastases, medical comorbidities precluding radical surgery, previous RT <12 months prior to recurrence, unability for MRI or PET-CT. Statistics; Simons two-stage design, with expected R0 of 30% by ITT and expected R0 increase to 45%, σ = 0:05; 1 − β= 0:8. Total sample size is 65 patients. Centers in Denmark and Norway are currently recruiting.