Aspirin as secondary prevention in colorectal cancer liver metastasis (ASAC trial): study protocol for a multicentre randomized placebo-controlled trial oleh Sheraz Yaqub, Bjørn Atle Bjørnbeth, Jon-Helge Angelsen, Claus Wilki Fristrup, Jon Erik Grønbech, Oskar Hemmingsson, Bengt Isaksson, Ingebjørg Soterud Juel, Peter Nørgaard Larsen, Gert Lindell, Frank Viborg Mortensen, Kim Erlend Mortensen, Magnus Rizell, Per Sandström, Oddvar Mathias Sandvik, Ernesto Sparrelid, Helena Taflin, Kjetil Taskén, The ASAC study group