Naltrexone (NTX) is an opioid antagonist that inhibits cell proliferation in vivo when administered in low
doses. Naltrexone in low doses are able to reduce tumor growth by interfering with cell signalling as well as by modifying
the immune system. It acts as an opioid growth factor receptor (OGFr) antagonist and the OGF-OGFr axis is an inhibitory
biological pathway present in human cancer cells and tissues, being a target for treatment with naltrexone low-dose
(LDN). Clinical trials have proposed a unique mechanism(s) allowing LDN to affect tumors. LDN shows promising
results for people with primary cancer of the bladder, breast, liver, lung, lymph nodes, colon and rectum. This short review
provides further evidence to support the role of LDN as an anticancer agent.