Apport des modèles expérimentaux dans la compréhension des douleurs en cancérologie

Thanks to therapeutic progress, cancer patients live longer, raising the important challenge of improved quality-of-life, particularly in terms of pain management. Cancer pain is specific. It is complex, chronic, and related not only to the disease and its consequences, but also to treatment. Two major components of cancer pain are generally described: pain due to over-reactive nociception and neuropathic pain related to tumor progression and treatment. The chronic nature of cancer pain involves an essential property of the nervous system, i.e. synaptic and cellular neuroplasticity. The development of animal models can be helpful in better understanding this neuroplasticity. Several anti-cancer drugs are known to generate such neuropathic pain in patients. In early work, when transposed to the rat and the mouse, this observation enabled the development of models mimicking the injection cycles of these drugs as they are used in human medicine. The second step was to study the specificity of cancer pain. This led researchers to develop models of pain directly related to cancer. The idea was to implant tumor cells in an anatomic compartment (bone marrow) mimicking the development of bone metastasis. This model has been very productive. In the present article, two types of models are described with the goal of demonstrating their innovative nature and, for each, their contribution to better understanding chronic neuropathic pain in general, and cancer pain in particular. Models of chronic neuropathic pain related to the neurotoxicity of two anti-cancer drugs, vincristin and oxaliplatin are discussed as well as models of bone cancer studied as generators of cancer pain. The study of animal models of pain should enable us to resolve one of the major enigmas of cancer pain: why is the intensity of the pain so variable from one treatment to another, one tumor to another, or even from one patient to another with the same tumor?