High MOR tumor expression has been associated with clinical severity and poor prognosis in patients with laryngeal carcinoma, [77], hepatocellular carcinoma [78], gastric cancer [79], and advanced prostate cancer [80], and several retrospective studies reported that patients who received general anesthesia with large amounts of opioids, show more cancer progression or recurrence than patients who received regional anesthesia or a lower amount of opioids [81,82,83]. The gene discussed is OPRM1; the disease is cancer.