Collagen Implant (Biological Mesh) Versus GM Flap for Reconstruction of Pelvic Floor After ELAPE in Rectal Cancer

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.