Opioids and cancer recurrence: A brief review of the literature

Opioids are the most commonly used analgesics during and after cancer surgery and in patients with advanced malignancies who suffer from moderate to severe pain. It has been suggested that opioids can promote cancer progression through different mechanisms including a direct effect on malignant cells, stimulation of angiogenesis and immunosuppression. In contrast, other studies have shown that opioids have anticancer effects. The results of clinical studies remain controversial with some evidence indicating that a high expression of the mu opioid receptor is an independent factor of tumor progression while other studies indicate that the administration of opioids perioperatively is associated with cancer recurrence. Unfortunately, all those clinical studies are retrospective and suffer from significant confounding variables and biases. To date, there is no solid evidence to suggest the avoidance of opioids in cancer patients with moderate to significant with the goal of reducing cancer recurrence. Some authors have suggested the use of spinal administration of opioids in order to reduce systemic effects. Careful use of opioids should be advise to reduce side effects or hyperalgesia in relation to specific needs of the patients.