Neuronal Sprouting and Reorganization in Bone Tissue Infiltrated by Human Breast Cancer Cells

Cancer pain, especially pain caused by metastasis to bone, is a severe type of pain, and unless the cause and consequences can be resolved, the pain will become chronic. As detection and survival among patients with cancer have improved, pain has become an increasing challenge, because traditional therapies are often only partially effective. Until recently, knowledge of cancer pain mechanisms was poor compared with understanding of neuropathic and inflammatory pain states. We now view cancer-induced bone pain as a complex pain state involving components of both inflammatory and neuropathic pain but also exhibiting elements that seem unique to cancer pain. In addition, the pain state is often unpredictable, and the intensity of the pain is highly variable, making it difficult to manage. The establishment of translational animal models has started to reveal some of the molecular components involved in cancer pain. We present the essential pharmacologic and neurobiologic mechanisms involved in the generation and continuance of cancer-induced bone pain and discuss these in the context of understanding and treating patients. We discuss changes in peripheral signaling in the area of tumor growth, examine spinal cord mechanisms of sensitization, and finally address central processing. Our aim is to provide a mechanistic background for the sensory characteristics of cancer-induced bone pain as a basis for better understanding and treating this condition.

The European Pain in Cancer survey sought to increase understanding of cancer-related pain and treatment across Europe. Patients with all stages of cancer participated in a two-phase telephone survey conducted in 11 European countries and Israel in 2006-2007. The survey screened for patients experiencing pain at least weekly, then randomly selected adult patients with pain of at least moderate intensity occurring several times per week for the last month completed a detailed attitudinal questionnaire. Of 5084 adult patients contacted, 56% suffered moderate-to-severe pain at least monthly. Of 573 patients randomly selected for the second survey phase, 77% were receiving prescription-only analgesics, with 41% taking strong opioids either alone or with other drugs for cancer-related pain. Of those prescribed analgesics, 63% experienced breakthrough pain. In all, 69% reported pain-related difficulties with everyday activities; however, 50% believed that their quality of life was not considered a priority in their overall care by their health care professional. Across Europe and Israel, treatment of cancer pain is suboptimal. Pain and pain relief should be considered integral to the diagnosis and treatment of cancer; management guidelines should be revised to improve pain control in patients with cancer.