Table 1.

Inclusion and exclusion criteria

Inclusion criteria	Exclusion criteria
Participants should have major LARS (LARS Score >29)	Known allergic reaction to melatonin
Participants should have undergone bowel continuity restoring surgery in relation to a surgical removal of a rectal tumour between the last 3 months and 24 months	Dementia as determined by Mini-Mental State Examination Score <24
Participants should be 18 years or older	Participation in another pharmacological intervention trial at the point of inclusion
Participants must sign an informed consent form	Completed any adjuvant oncological treatment within the last 3 months prior to inclusion
	Ongoing oncological treatment
	Rotor or Dubin-Johnson syndrome, epilepsy, systemic lupus erythematosus, rheumatoid arthritis, Parkinson’s disease, spinal cord injury and multiple sclerosis
	Severe liver disease is defined as transaminases above three times the normal levels, and severe kidney disease is defined as eGFR below 40 mL/min.
	Daily ongoing hypnotic treatment
	Pre-existing medical sleep disorder diagnosed before the diagnosis of rectal cancer (ie, sleep apnoea, restless legs, narcolepsy)
	Work involving nightshifts
	Daily alcohol consumption above five units of alcohol
	Predictable poor compliance (due to pre-existing psychiatric disease, dementia or not able to read or speak sufficient Danish)
	Pregnant or breast feeding
	Severe, life-threatening medical condition, which implies that patients cannot participate in the study course (eg, metastatic disease, local recurrence, stroke, AMI)
	Women not in menopause (defined as no menstruation during the last 12 months) should not be pregnant. Furthermore, reproductive women should use a secure birth control (intrauterine devices, hormonal contraceptives including oral pills, patches, vaginal rings and injections) during the entire period of the trial.

AMI, acute myocardial infarction; eGFR, Estimated Glomerular Filtration Rate; LARS, low anterior resection syndrome.