The trial compares two different techniques for reconstruction of the lesser pelvic floor after an extended abdominoperineal excision for locally advanced rectal cancer. The alternative reconstruction techniques in the trial are:

• a technique using a gluteus maximus myocutaneous flap or
• a technique using an acellular porcine collagen implant (biological mesh)

The primary endpoint will be physical performance six months from operation and our hypothesis is that the technique using an acellular porcine implant will cause less impaired physical performance compared to the technique using a myocutaneous flap.

The study is interventional, randomized and by definition a comparative effectiveness research project.

Extended abdominoperineal excision (EAPE) of the rectum is the potentially curative operation for rectal carcinomas too low for primary anastomosis, especially if the levator and sphincter musculature is infiltrated. This enlarged operation, when the levator musculature is excised en bloc with the rectum, creates a large defect. Primary closure is often not possible, and reconstruction with prosthetic material or a myocutaneous flap is necessary to avoid a perineal hernia. Implantation of a collagen sheet (biological mesh) has shown preliminary good results and on the other hand, the use of a gluteus myocutaneous flap is routine in many clinics. There is a lack of scientific evidence to prove which method is better for the reconstruction of the lesser pelvic floor.

The current study aims to compare the two reconstruction techniques.

Centres that treat locally advanced rectal cancers with the extended abdominoperineal excision of rectum (EAPE)[Holm et al 2007] can participate provided that:

1. the operative technique is standardized according to the study protocol
2. the centre/unit has resources for examinations of participants by a physiotherapist or a nurse
3. the centre/unit has one investigator in charge of the study locally
4. the centre/unit has an operative volume that enables at least 6 patients to be included/randomised during the anticipated three year study phase for inclusions

Centres that do not operate the rectal cancers included in this study can participate by arranging the preoperative examination and physical tests as well as follow-up of patients that are referred to other centres for the operation. In these cases the operating centre cares for the randomisation, operation and start of postoperative rehabilitation while the study follow-up and final rehabilitation can be completed at the patients' primary referral hospital. The primary referral hospital needs a site investigator in charge of study patients just like centres that do the operations.

Patients with primary or recurrent cancers of rectal origin can be included but individual patients can be included only once. Concomitant therapies are allowed and preoperative or postoperative radiation therapy and/or chemotherapy may be given or not according to local multidisciplinary team (MDT) decisions.

Inclusion Criteria:

• Adult (18 years or older) rectal cancer patients where wide resection of pelvic floor muscles together with rectum and anal canal have made reconstruction of pelvic floor necessary i.e. primary suture of pelvic floor in the midline is not possible. Resection of coccyx is optional.

Exclusion Criteria:

• Age less than 18 years
• Very large resections including partial resection of sacrum and patients considered for bilateral flap reconstruction
• Large concomitant resection of vaginal wall where total (vaginal) wound closure is not an option
• Expected survival less than one year at operation
• Patient do not sign informed consent document