SPHK1 and reproductive system neoplasm: Subgroup analysis of cancer type showed that increased SPHK1 expression was significantly related to poor OS in patients with digestive system malignancies (HR = 1.79, 95% CI: 1.39-2.31, P < 0.001), urinary system cancers (HR = 1.49, 95% CI: 1.20-1.84, P < 0.001), head and neck cancers (HR = 2.08, 95% CI: 1.48-2.91, P < 0.001), and LC (HR = 2.15, 95% CI 1.39-3.35, P = 0.001), but no significant relationship was observed in patients with reproductive system tumors (HR = 1.71, 95% CI: 0.34-8.64, P = 0.519) and BC (HR = 1.16, 95% CI: 0.66-2.02, P = 0.608).