Opiophobia in Cancer Biology-Justified? - The Role of Perioperative Use of Opioids in Cancer Recurrence

Opioids remain the standard of care in the provision of analgesia in the patient undergoing cancer surgery preoperatively. The effects of opioids on tumor growth and metastasis have been discussed for many years. In recent years their use as part of the perioperative pain management bundle in the patients undergoing cancer surgery has been thought to promote cancer recurrence and metastasis. This narrative review highlights earlier and more recent in vitro, in vivo and human retrospective studies that yield conflicting results as to the immune-modulatory effects of morphine on tumor biology. The article examines and explains the discrepancies with regards to the seemingly opposite results of morphine in the tumor milieu. The results of both, earlier studies that demonstrated procarcinogenic effects versus the data of more recent refined rodent studies that yielded neutral or even anti-carcinogenic effects are presented here. Until the results of prospective randomized controlled trials are available to clarify this important question, it is currently not warranted to support opiophobia and opioids continue to constitute a pivotal role in the pain management of cancer patients.