The incidence of cancer continues to increase, despite considerable investment in prevention. Additionally, with improved oncological treatments, more people are living with, or being cured of, cancer, and many of these will have disease or treatment-related chronic pain, requiring analgesia. Currently, there is much interest in how analgesics and anaesthetics may impact on cancer biology (especially cancer recurrence and metastases) and consequently on survival. There are at least two areas of particular interest: first, how regional techniques or specific general anaesthetics used for cancer surgery may impact long-term survival, and secondly, how both endogenous and exogenous opioids may modulate cancer biology. It is essential to understand the possible mechanisms of these potential interactions so that patients may be given the best chance of pain-free survival.