This prospective, multi-centre, randomised clinical trial aims to compare the effect of neoadjuvant chemoradiotherapy versus primary surgery on circulating tumor cells (CTCs) in patients with stage II-III rectal cancer without circumferential resection mar-gin involvement. CTCs are considered a promising biomarker for disease dissemination and treatment response. Patients will be randomized to either primary surgical resection with total mesorectal excision or long-course neoadjuvant chemoradiotherapy followed by surgery. Serial blood samples will be collected at predefined time points to assess the presence and dynamics of CTCs. Secondary endpoints include perioperative morbidity and mortality, local recurrence rate, disease-free survival, and overall survival. The results of this study may provide new insights into the prognostic role of CTCs and contribute to optimising treatment strategies for rectal cancer.