STAR-TREC: An International Three-arm Multicentre, Partially Randomised Controlled Trial Incorporating an External Pilot.

[AIM] Organ saving treatment for early-stage rectal cancer can reduce patient reported side effects compared to standard total mesorectal excision (TME) and preserve quality of life (QOL). An optimal strategy for achieving organ preservation and longer-term oncological outcomes are unknown, thus there is a need for high quality trials.

[METHOD] Can we Save the rectum by watchful waiting or TransAnal surgery following (chemo)Radiotherapy versus Total mesorectal excision for early REctal Cancer (STAR-TREC) is an international 3-arm multi-centre, partially randomised controlled trial incorporating an external pilot. In phase III, patients with cT1-3b N0 tumours, ≤40mm in diameter, who prefer organ preservation are randomised 1:1 between mesorectal long course chemoradiation versus mesorectal short course radiotherapy, with selective transanal microsurgery. Patients preferring radical surgery receive TME. STAR-TREC aims to recruit 380 patients to organ preservation and 120 to TME surgery. The primary outcome is the rate of organ preservation at 30 months. Secondary clinician reported outcomes include acute treatment-related toxicity, rate of non-operative management, non-regrowth pelvic tumour control at 36 months, non-regrowth disease free survival at 36 months, and overall survival at 60 months and patient reported toxicity, health related QOL at baseline, 12 and 24 months. Exploratory biomarker research uses circulating tumour DNA to predict response and relapse.

[DISCUSSION] STAR-TREC will prospectively evaluate contrasting therapeutic strategies and implement new measures including a smaller mesorectal target volume, 2-step response assessment and non-operative management for complete response. The trial will yield important information to guide routine management of patients with early-stage rectal cancer.