A new clinically-relevant rat model of letrozole-induced chronic nociceptive disorders.

Among postmenopausal women with estrogen receptor-positive breast cancer, more than 80% receive hormone therapy including aromatase inhibitors (AIs). Half of them develop chronic arthralgia - characterized by symmetric articular pain, carpal tunnel syndrome, morning stiffness, myalgia and a decrease in grip strength - which is associated with treatment discontinuation. Only a few animal studies have linked AI treatment to nociception, and none to arthralgia. Thus, we developed a new chronic AI-induced nociceptive disorder model mimicking clinical symptoms induced by AIs, using subcutaneous letrozole pellets in ovariectomized (OVX) rats. Following plasma letrozole dosage at the end of the experiment (day 73), only rats with at least 90 ng/ml of letrozole were considered significantly exposed to letrozole (OVX + high LTZ group), whereas treated animals with less than 90 ng/ml were pooled in the OVX + low LTZ group. Chronic nociceptive disorder set in rapidly and was maintained for more than 70 days in the OVX + high LTZ group. Furthermore, OVX + high LTZ rats saw no alteration in locomotion, myalgia or experimental anxiety during this period. Bone parameters of the femora were significantly altered in all OVX rats compared to Sham+vehicle pellet. A mechanistic analysis focused on TRPA1, receptor suspected to mediate AI-evoked pain, and showed no modification in its expression in the DRG. This new long-lasting chronic rat model, efficiently reproduces the symptoms of AI-induced nociceptive disorder affecting patients' daily activities and quality-of-life. It should help to study the pathophysiology of this disorder and to promote the development of new therapeutic strategies.

Minimizing chemotherapy-induced peripheral neuropathy: preclinical and clinical development of new perspectives.

INTRODUCTION: Chemotherapy-induced peripheral neuropathies (CIPN) are a dose-limiting adverse effect of certain anticancer drugs (platinum salts, vinca alkaloids, taxanes, bortezomib, thalidomide, epothilones, eribulin). CIPN are mainly responsible for sensory disturbances and are associated with a decrease in quality of life. After the end of chemotherapy, CIPN can last for several months and even years. Unfortunately, recent meta-analyses of clinical trials have demonstrated that there is no univocal gold standard for the prevention and treatment of CIPN. AREAS COVERED: Using animal models of CIPN, several new strategies to prevent or treat CIPN are under development. These new strategies involve several pathways, including ion channels, neuroprotectants, glutamatergic neurotransmission, oxidative stress, cannabinoid system, inflammation, and mitochondrial functions. EXPERT OPINION: To date, based on meta-analyses of clinical trials, no drug can be proposed as a gold standard to prevent or treat CIPN. Consequently, there is a strong discrepancy between the optimistic results of animal studies and the poor outcomes of clinical trials. Pain assessment in preclinical and clinical studies is probably not the best outcome measurement tool and all these studies should include composite outcomes including the full complexity of CIPN symptoms, such as positive symptoms (pain, paresthesia, and dysesthesia) and negative ones (numbness).

Prevention of oxaliplatin-induced peripheral neuropathy by a polyamine-reduced diet-NEUROXAPOL: protocol of a prospective, randomised, controlled, single-blind and monocentric trial.

INTRODUCTION: Oxaliplatin remains the most widely used chemotherapeutic agent for treating advanced colorectal cancer but its efficacy is hampered by dose-limiting neurotoxicity manifested by a painful polyneuropathy. Oxaliplatin-induced peripheral neuropathy (OIPN) is characterised by acute and transient cold hyperaesthesia in the hours and days following oxaliplatin infusion (>90% of patients), but also by retarded chronic neuropathy due to the repetition of chemotherapy cycles (30-50% of patients). OIPN impairs the health-related quality of life (HRQOL) of patients and no preventive or curative strategies have as yet proven effective. A polyamine-reduced diet (PRD) has recently demonstrated its efficacy to prevent OIPN in animals without adverse effects. METHODS AND ANALYSIS: The NEUROXAPOL trial is a prospective, randomised, controlled, single-blind, monocentric and interventional study. This trial is aimed at evaluating the efficacy and feasibility of a PRD compared to a normal polyamine containing diet to prevent OIPN in patients treated by oxaliplatin-based chemotherapy. Patients (n=40 per group) will be randomly assigned to receive either a PRD or a normal diet before and during the chemotherapy regimen. The main objectives are to improve the cold pain thresholds, neuropathic pain symptoms, comorbidities (anxiety and depression) and HRQOL of patients. The primary end point is the assessment of cold pain thresholds 2 weeks after the third cycle of chemotherapy. The secondary end points are the evaluation of thermal pain thresholds, the grade of neuropathy, neuropathic pain, symptoms of anxiety and depression and HRQOL, until the 12th cycle of chemotherapy. ETHICS AND DISSEMINATION: The study was approved by an independent medical ethics committee 1 (CPP Sud Est 1, Saint Etienne, France) and registered by the competent French authority (ANSM, Saint Denis, France). The results will be disseminated in a peer-reviewed journal and presented at international congresses. TRIAL REGISTRATION NUMBER: NCT01775449.