• In this longitudinal study, 171 patients were evaluated and compared based on the radiation therapy they received.
• Bowel function was assessed longitudinally with Memorial Sloan Kettering Cancer Center and Wexner scores every 6 months after restoration of bowel continuity. Patients with at least two follow-up visits were included.

Background Despite advances in the neoadjuvant chemoradiation therapy and anal sphincter-preserving surgeries for rectal cancer, bowel dysfunction is still unavoidable which negatively affect the patients' quality of life. In this longitudinal study, The aim of this study was to investigate the changes in bowel function with follow up time and the effect of the neoadjuvant chemo radiotherapy on bowel function following low anterior resection for rectal cancer.

Materials and methods In this study, 171 patients with rectal cancer who underwent low anterior resection between 2012 and 2018 were included. Bowel function was assessed longitudinally with Memorial Sloan Kettering Cancer Center and Wexner scores every 6 months after restoration of bowel continuity. Patients with at least two follow-up visits were included.

Inclusion Criteria:

• Patients of both sexes,
• Aged between 18 and 75 years,
• Patients with mid and upper rectal cancer (6-15) cm from the anal verge(AV) with or without preoperative chemo radiotherapy.
• Patients who underwent low anterior resection(LAR).
• Patients who were followed up with at least two outpatient visits for bowel function assessment.

Exclusion Criteria:

• Patients with recurrent rectal tumors,
• Surgically unfit patients,
• Patients with tumors infiltrating the puborectalis muscle or external sphincter.
• Patients with preoperative fecal incontinence.
• Patients who were followed up only once in the outpatient clinic.
• Patients with lower rectal cancer less than 6cm from AV,
• Patients who underwent abdominoperineal resection(APR) or intersphincteric resection(ISR).