Pain Phenotyping of Patients With Bone Cancer Pain

Cancer patients in palliative care point to pain as their most important and most feared symptom. Bone metastases are a common cause of cancer pain, and the patients are prone to transient severe pain exacerbations (breakthrough pain), which can occur spontaneously or be triggered by movement. Patients with bone metastases experience pain of such high intensity, that it affects not only physical activity, but also sleep, mood and social relations. This results in poor quality of life for the patients and poses an increasing clinical and socio-economical problem. The pain is difficult to treat and often requires high opioid doses which results in unacceptable adverse effects, and there is an unmet need of novel therapeutic options and treatment strategies. Animal models of cancer-induced bone pain have suggested that pain arising from metastatic bone disease involve neuropathic and nociceptive pain mechanisms and, importantly, mechanisms that are specific to cancer-induced bone pain. Significant neuronal sprouting can occur at the metastatic site, and the inherent pain control system is found altered in animal models of cancer-induced bone pain; a system that can be exploited for treatment strategies and in the development of new analgesia. Yet, it is not known how the pre-clinical findings translate to patients. Quantitative sensory testing is a psychophysical method that uses a battery of sensory stimuli with predetermined physical properties, thus allowing the capture and quantification of stimulus-evoked negative and positive sensory phenomena in humans. Conditioned pain modulation is a psychophysical experimental measure of the endogenous pain inhibitory pathway in humans, which can be used to detect an impairment of the descending inhibitory pain pathway. This study aims to perform pain phenotyping of patients suffering from cancer-induced bone pain, through pain specific questionnaires, quantitative sensory testing and conditioned pain modulation.