Active Surveillance vs Adjuvant Chemoradiotherapy for Locally Resected Intermediate-Risk T1 Rectal Cancer

The goal of this clinical trial is to learn if close follow-up alone (active surveillance) works as well as radiation combined with chemotherapy (chemoradiotherapy) after removing early rectal cancer in adults. The main questions it aims to answer are: 1. Does active surveillance cause fewer serious adverse events than chemoradiotherapy within 3 years? Serious adverse events include a permanent or temporary ostomy (a surgical opening in the belly to pass stool), major bowel problems, or severe treatment-related complications. 2. Is active surveillance as safe as chemoradiotherapy in preventing cancer from coming back or spreading within 3 years? Researchers will compare active surveillance to chemoradiotherapy to see if surveillance causes fewer serious adverse events while keeping cancer outcomes comparable. To join this study, participants must be adults who had an early-stage rectal cancer (T1) removed by an endoscopic procedure, and whose removed tumor showed certain features that raise the risk of cancer cells remaining nearby. Participants will be randomly placed in one of two groups: 1. Active surveillance group: Participants will have regular checkups, blood tests, flexible camera exams of the bowel (rectoscopy), scans of the pelvis and abdomen, and colonoscopy on a set schedule for 5 years. If cancer comes back, doctors will propose further treatment options. 2. Chemoradiotherapy group: Participants will receive radiation to the pelvis along with a chemotherapy pill (capecitabine) or an intravenous (IV) chemotherapy drug (5-FU) for about 5 weeks. After treatment, they will have regular checkups and scans for 5 years.

NCT Number	NCT07669298
Lead Sponsor	Medical University of Gdansk Collaborators: University of Oslo, Maria Sklodowska-Curie National Research Institute of Oncology, Centre Hospitalier Universitaire Dupuytren de Limoges (CHUL), Vestre Viken Hospital Trust, Universitätsklinikum Hamburg-Eppendorf, Karolinska Institutet, University Hospital, Akershus, University of Roma La Sapienza, Hospital Clinic of Barcelona, Leuven University Medical Center, University Hospital, Ghent, Sorlandet Hospital HF, Northern Norway Regional Health Trust, Helse Stavanger HF, Haukeland University Hospital, St. Olavs Hospital
Conditions	Rectal Cancer
Enrollment	480 participants
Start Date	2026-06-14
Primary Completion	2037-06 (estimated)
Study Completion	2037-06 (estimated)
Updated on ClinicalTrials.gov	2026-06-25