Contact radiotherapy for rectal cancer (CORRECT): study protocol for a multicentre randomised phase II trial.

introductionNon-operative management of early-stage rectal cancer is increasingly recognised as a subject of significant clinical and research interest. Contact X-ray brachytherapy (CXB) offers an alternative to surgery in appropriately selected cases. Current clinical evidence suggests the use of CXB in combination with chemoradiotherapy (CRT). Although proven effective, no randomised evidence exists for the combination of CXB and short-course radiotherapy (SCRT). In this Swedish national randomised phase II trial, we aim to compare the combination of CXB with either CRT or SCRT in patients with early-to-intermediate rectal cancer. METHODS AND ANALYSIS: A total of 110 eligible, operable patients with early-to-intermediate rectal cancer (cT1-cT3ab), with tumours measuring <5 cm in largest diameter, involving <50% of the rectal circumference, N0-N1 (≤3 nodes <8 mm in diameter), located ≤10 cm from the anal verge and MX/M0, are randomised into two arms: standard arm (A) CXB with CRT and experimental arm (B) CXB with SCRT. The contact radiotherapy for rectal cancer (CORRECT) trial aims to evaluate whether the experimental treatment is non-inferior to standard treatment with respect to the primary endpoint 2-year organ preservation rate. On demonstrating non-inferiority in oncological outcomes compared with CXB+CRT, the combination of CXB+SCRT could pave the way for establishing a new standard of care for organ preservation in early-to-intermediate rectal cancer for patients who wish to avoid surgery. ETHICS AND DISSEMINATION: CORRECT is conducted in accordance with research ethical approval (2024-02762-01) granted by the Swedish Research Ethics Committee on 4 June 2024. Informed consent will be obtained from all trial participants. The trial results will be published in international peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT06501053.