Late complications after treatment for colorectal and anal cancer are to some degree inevitable due to the rather aggressive treatment modalities both with surgery and chemo-radiation therapy. Stool-related late complications have a major impact on patients’ quality of life. The objective of this study was to investigate stool and bowel movements as late complications to colorectal and anal cancer treatment.

We performed a prospective cohort study from a single center using patient reported outcome measurements. We included patients who had surgery for colorectal and anal cancer from October 2019 to January 2022. This was supplemented by a subgroup of patients with late complications after chemo-radiation therapy for anal cancer. The study population comprised 293 patients. The main outcome included descriptive data on stool and bowel movement related complications. We used the low anterior resection symptom score (LARS), St Mark´s incontinence score, Bristol stool form scale, patient assessment of constipation symptoms score (PAC-SYM), colostomy impact factor, and self-rated health on a visual analog scale as measurement tools.

We present prospective data on the incidence of stool and bowel-related symptoms in a large cohort of 293 patients. The low anterior resection symptom score was median 36 (range 24-41) in patients with rectum cancer, for patients with anal cancer it was 39 (4-41), for patients with a right or left sided hemicolectomy it was 26 (4-41) and 25 (0-41), respectively. A low anterior resection symptom score score above 30 is interpretated as the patients have major bowel problems, when it is between 21-29 the patients have minor symptoms. We found significant differences of both LARS (p = 0.005) and the St Mark´s incontinence score (p = 0.005) between patients with rectum cancer and anal cancer compared with patients with colon cancer. 
Our data showed that patients with rectum and anal cancer had a lower median self-rated health of 67% than patients who had undergone treatment with a right or left sided hemicolectomy, they had a median self-rated health of 76 %,

The self rated health were significantly worse for patients with rectum and anal cancer compared with patients with colon cancer (p= 0.002) indicating that  bowel dysfunction can imply the patients overall self-rated health.

Patients who had surgery for rectum cancer had in 90% of the cases major low anterior resection syndrome (LARS). Patients who underwent surgery for colon cancer would in about one third of the cases experience stool or bowel movement impairments. Patients with anal cancer who had chemo-radiation therapy experienced a very high degree of stool and bowel movement impairment.