Home-Based Physical Activity Intervention for Taxane-Induced CIPN

The use of taxanes in breast cancer chemotherapy regimens is considered standard first line therapy.1 However, taxanes are known to induce peripheral neuropathy, from 59-87% for paclitaxel and from 11-64% for docetaxel. 2-4 Sensory manifestations can include pain; numbness, tingling, \& burning; diminished proprioception, and decreased vibration and touch sensation. 5-6 Motor symptoms such as lower extremity muscle weakness and impaired balance has been reported. 7 Currently, peripheral neuropathy remains a significant toxicity resulting in taxane chemotherapy dose reductions or discontinuation, with no evidence-based preventative or treatment strategies are available. 8 Taxanes induce sensory and motor neuropathy by inducing both mitochondrial and vascular dysfunction.9 In rodents, treatment with taxanes resulted in swollen, vacuolated axonal mitochondria that are functionally impaired, producing a chronic energy deficit.10 In addition, toxic effects to the endothelial cells of the vasa nervorum (small arterioles that supply peripheral nerves) in the dorsal root ganglia attenuates blood flow to neurons, resulting in endothelial cell death. 11 These findings suggest that both mitochondrial impairment and vascular damage are major mechanisms that underlie the development of taxane-induced peripheral neuropathy, manifesting as sensory manifestations and neuropathic pain. 9-12 Mitochondrial and vascular dysfunctions lead to sensory loss and reduced muscle strength, functions dependent upon cellular mitochondria to generate energy in the form of ATP (adenosine triphosphate). Thus, mitochondrial dysfunction results in the loss of energy-generating capability, and vascular impairment deprives muscle and nerve cells of oxygen-rich nutrients, further impairing neuronal function. A limited number of human and animal studies have demonstrated that exercise stimulates endothelium-dependent vasodilation and vascular endothelial growth factor (VEGF) expression, increasing endoneurial blood flow and energy generating capacity through mitochondrial protein synthesis and glycolysis, 13, 14 The proposed exercise intervention addresses gait/balance impairments and motor (resistance) components of taxane-induced peripheral neuropathy. The mechanism by which the intervention achieves the proposed outcomes is though 1) increasing endoneurial blood flow to peripheral nerves and mitochondria resulting in reduction in neuropathic symptoms (including pain) and clinical manifestations of peripheral neuropathy, while improving gait/balance in those with persistent neuropathy; 2) The subsequent increase in nutrient supply allows the mitochondria to function more efficiently, and may alleviate the neuropathic manifestations of taxane-induced peripheral neuropathy. Specific Aims: In a sample of patients who completed a taxane-containing chemotherapy regimen (\> 1 year) for breast cancer and who have a persistent neuropathy (VAS score of \> 3) the specific aims of this RCT are: 1. To test the efficacy of a 16-week -delivered program of gait/balance training plus resistance exercise, compared to an educational attention control condition in increasing muscle strength, improving gait/balance and nerve conduction parameters, decreasing the severity of taxane-induced peripheral neuropathy symptoms, and increasing quality of life. 2. To evaluate for differences in muscle strength, gait/balance, sensory (sural) and motor (peroneal) nerve conduction, peripheral neuropathy symptoms, and quality of life (QOL) between patients who receive the exercise program, compared to those in an educational attention control condition controlling for age, BMI, taxane cycles and intervals, neuropathic pain, neuropathy/pain medications, current resistance exercise participation and falls/near falls experienced