Reflecting on Cancer Pain as Constant Acute Pain, not Chronic Pain. 'Known Knowns, Known Unknowns, Unknown Unknowns'.

Purpose of review: to explore a paradigm shift in the definition of opioid-responsive cancer pain in this hypothesis-driven review. Opioid-responsive cancer pain may be misplaced within the definition of chronic pain, chronic pain takes three months to establish, early effective control is worthwhile to achieve. RECENT: findings, from a bench-to-bed perspective, debates the interpretation of results supporting the hypothesis that opioid-responsive cancer pain could remain 'constant acute pain', with explanations, best solutions, for tolerance and/or addiction, in cancer patients compared to those with chronic pain from other conditions. Unraveling the unique apparent properties of opioid-responsive cancer pain empowers knowledge of the process by which acute pain may have the potential to remain acute in nature and not transition into chronic pain. Findings outlined defend the hypothesis of probable sustained acute nature of opioid-responsive cancer pain, importance of early, sustained pain control, opioid reduction and further exploration of this hypothesis in clinical practice.