The subgroup analysis of tumor type demonstrated negative impact of elevated MDK on OS in patients with pancreatic cancer (pooled HR = 2.28; 95% CI = 1.47–3.55; P < 0.001), gastric cancer (pooled HR = 2.89; 95% CI = 1.47–5.70; P = 0.002), NSCLC (pooled HR = 1.78; 95% CI = 1.27–2.55; P = 0.001), and other cancers (pooled HR = 2.20; 95% CI = 1.56–2.61; P < 0.001), while MDK had no relevance with OS in the patients with OSCC (pooled HR = 1.68; 95% CI = 0.84–3.36; P = 0.145) or HNSCC (pooled HR = 1.56; 95% CI = 0.96–2.51; P = 0.075). This evidence concerns the gene MDK and head and neck squamous cell carcinoma.