PDCD1 and colorectal cancer: Similarly, numerous studies all around the world could not confirm a significant association between PD-1 rs2227981 and susceptibility or protection to BC (Haghshenas et al., 2011), colorectal cancer (Savabkar et al., 2013), NSCLC (Ma et al., 2015) and epithelial ovarian cancer (Li et al., 2016).