Inclusion Criteria:  Patient: male and female, age ≥18 years Tumour: rectal cancer Surgery: anterior resection (high or low) with colorectal or coloanal anastomosis, or intersphincteric resection, or pull-through Symptoms: Low Anterior Resection Syndrome (LARS score >20) refractory to medical treatment at 3 months after rectal surgery (or after temporary stoma closed) Straight or pouch colonic reconstruction Surgery alone or with neoadjuvant therapy (chemoradiotherapy, short course radiotherapy, induction chemotherapy) Signed and dated informed consent Patient affiliated to a social security system or beneficiary of the same Willingness and ability to comply with scheduled visits, treatment plans, laboratory tests, and other study procedures  Exclusion Criteria:  Anal cancer Anal surgery in the last 3 months Acute/painful perianal disease Ongoing adjuvant treatment Contraindication for BOTOX-A (known hypersensitivity to botulinum toxin type A or to albumin, infection at the proposed injection site, severe myasthenia) Have received BOTOX-A in perianal region in the previous 3 months General anesthesia performed less than a month Impossibility of performing a rectoscopy (eg: anal stenosis) Recent history (<12 months) of myocardial infarction and / or arrhythmias not reduced by appropriate treatment Subject with a significant deficit of clinical or subclinical neuromuscular transmission (myasthenia or Lambert-Eaton syndrome) or with peripheral motor neuropathy (such as amyotrophic lateral sclerosis or motor neuropathy) Treatment that directly or indirectly interferes with neuromuscular transmission (aminoglycosides, curare, anticholinesterase, aminoquinoline, cyclosporine, etc.) History of neuromuscular disorders Anal clinical examination suggesting the presence of an anorectal abscess Pregnant woman or breastfeeding woman Women of child-bearing potential (WOCBP)* not using effective contraception (oestrogen-progesteron combined contraceptives or intra uterine device) since at least 7 days and during all the duration of the study Persons deprived of their liberty or under measure of judicial protection (curatorship or guardianship) or unable to give their consent Any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol or follow-up schedule, as assessed by investigator.