Animal models of cancer pain

The incidence of cancer pain is high in patients with advanced disease as well as in patients undergoing active treatment for solid tumors. Further, modern cancer therapies have significantly increased survival rates, making effective pain control critical as unrelieved pain significantly decreases the quality of life of such patients. Thus, the goal of pain management is to not only alleviate pain, but also maintain the patient's normal quality of life. To meet this challenge, novel analgesics with greater efficacy but fewer side effects are needed for alleviating cancer-induced pain. Recent advances in understanding the mechanism(s) of cancer pain have been assisted by the development of several rodent models that have shown that there are unique tumor-induced central and peripheral anatomical and pathophysiological changes, as well as physical and biochemical interactions between nerves, surrounding tissue, and tumor cells, which may be important to understand in order to develop better treatment strategies for cancer-associated pain. This review focuses on bone cancer pain models, nonbone cancer pain models, cancer invasion pain models, cancer chemotherapeutic-induced peripheral neuropathy, and spontaneous-occurring cancer pain models, all of which have contributed to a better understanding of the basis for tumor-induced pain and have allowed exploration of novel mechanistic-based therapies.