NDRG2 and lung cancer: Regarding cancer type subgroup analysis, the overall results showed that the negative expression of NDRG2 had an unfavorable impact on OS in patients with digestive system malignancies (HR = 1.78, 95% CI: 1.48–2.13, P < .001), breast cancer (HR = 1.53, 95% CI: 1.21–1.94, P < .001), prostate cancer (HR = 15.27, 95% CI: 1.13–32.58, P = .006), and lung cancer(HR = 1.71, 95% CI: 1.24–2.34, P = .001), but such association was not observed for patients with renal cell carcinoma (HR = 4.70, 95% CI: 0.94–23.36, P = .059).