Overall, there was no evident relation between the PD-1.9 and cancer risk (T vs. C: OR = 0.98, 95% CI = 0.89-1.07, P = 0.629; TT vs. CC: OR = 0.96, 95% CI = 0.77-1.19, P = 0.693; CT vs. CC: OR = 0.98, 95% CI = 0.86-1.11, P = 0.744; TT+CT vs. CC: OR = 0.98, 95% CI = 0.86-1.11, P = 0.694; TT vs. CT+CC: OR = 0.97, 95% CI = 0.82-1.15, P = 0.702, Figure 3 and Table 2). Here, PDCD1 is linked to cancer.