In a group of 76 patients with locally advanced rectal cancer (LARC), the expression of SMAD3 and phosphorylated SMAD3 in preoperative tumour tissues was assessed by immunohistochemistry, and SMAD3 polymorphisms (rs35874463, rs1065080, rs1061427, rs17228212, rs744910, and rs745103) in relation to tumour regression grade and patient prognosis. Here, SMAD3 is linked to rectal cancer.