From the University of Texas MD Anderson Cancer Center, Houston, TX (Drs. Narayanan, Lopez, Chaoul, Liu, Milbury, and Cohen, and Ms. Mallaiah); the University of Texas Health Science Center at Tyler (Dr. Meegada); and Texas Tech University Health Sciences Center, Lubbock, TX (Ms. Francisco).
Abstract
Objective: To review the effects of yoga as an adjunct supportive care modality alongside conventional cancer treatment on quality of life (QOL), physical and mental health outcomes, and physiological and biological measures of cancer survivors.
Methods: Nonsystematic review of the literature.
Results: Yoga therapy, one of the most frequently used mind-body modalities, has been studied extensively in cancer survivors (from the time of diagnosis through long-term recovery). Yoga affects human physiology on multiple levels, including psychological outcomes, immune and endocrine function, and cardiovascular parameters, as well as multiple areas of QOL. It has been found to reduce psychological stress and fatigue and improve QOL in cancer patients and survivors. Yoga has also been used to manage symptoms such as arthralgia, fatigue, and insomnia. In addition, yoga offers benefits not only for cancer survivors but also for their caregivers.
Conclusion: As part of an integrative, evidence-informed approach to cancer care, yoga may provide benefits that support the health of cancer survivors and caregivers.
A diagnosis of cancer and adverse effects related to its treatment may have negative effects on quality of life (QOL), contributing to emotional and physical distress in patients and caregivers. Many patients express an interest in pursuing nonpharmacological options, alone or as an adjunct to conventional therapy, to help manage symptoms. The use of complementary medicine approaches to health, including nonpharmacological approaches to symptom management, is highest among individuals with cancer.1 According to a published expert consensus, integrative oncology is defined as a “patient-centered, evidence-informed field of cancer care that utilizes mind and body practices, natural products, and/or lifestyle modifications from different traditions alongside conventional cancer treatments. Integrative oncology aims to optimize health, QOL, and clinical outcomes across the cancer care continuum and to empower people to prevent cancer and become active participants before, during, and beyond cancer treatment.”2 A key component of this definition, often misunderstood in the field of oncology, is that these modalities and treatments are used alongside conventional cancer treatments and not as an alternative. In an attempt to meet patients’ needs and appropriately use these approaches, integrative oncology programs are now part of most cancer centers in the United States.3-6
Because of their overall safety, mind-body therapies are commonly used by patients and recommended by clinicians. Mind-body therapies include yoga, tai chi, qigong, meditation, and relaxation. Expressive arts such as journaling and music, art, and dance therapies also fall in the mind-body category.7 Yoga is a movement-based mind-body practice that focuses on synchronizing body, breath, and mind. Yoga has been increasingly used by patients for health benefits,8 and numerous studies have evaluated yoga as a complementary intervention for individuals with cancer.9-14 Here, we review the physiological basis of yoga in oncology and the effects of yoga on biological processes, QOL, and symptoms during and after cancer treatment.
Physiological Basis
Many patients may use mind-body programs such as yoga to help manage the psychological and physiological consequences of unmanaged chronic stress and improve their overall QOL. The central nervous system, endocrine system, and immune system influence and interact with each other in a complex manner in response to chronic stress.15,16 In a stressful situation, the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS) are activated. HPA axis stimulation leads to adrenocorticotrophic hormone production by the pituitary gland, which releases glucocorticoid hormones. SNS axis stimulation leads to epinephrine and norepinephrine production by the adrenal gland.17,18 Recently, studies have explored modulation of signal transduction between the nervous and immune systems and how that may impact tumor growth and metastasis.19 Multiple studies, controlled for prognosis, disease stage, and other factors, have shown that patients experiencing more distress or higher levels of depressive symptoms do not live as long as their counterparts with low distress or depression levels.20 Both the meditative and physical components of yoga can lead to enhanced relaxation, reduced SNS activation, and greater parasympathetic tone, countering the negative physiological effects of chronic stress. The effects of yoga on the HPA axis and SNS, proinflammatory cytokines, immune function, and DNA damage are discussed below.
Biological Processes
Nervous System
The effects of yoga and other forms of meditation on brain functions have been established through several studies. Yoga seems to influence basal ganglia function by improving circuits that are involved in complex cognitive functions, motor coordination, and somatosensory and emotional processes.21,22 Additionally, changes in neurotransmitter levels have been observed after yoga practice. For instance, in a 12-week yoga intervention in healthy subjects, increased levels of thalamic gamma-aminobutyric acid (GABA) in the yoga group were reported to have a positive correlation with improved mood and decreased anxiety compared with a group who did metabolically matched walking exercise.23 Levels of GABA, an inhibitory neurotransmitter, are decreased in conditions such as anxiety, depression, and epilepsy.24 Yoga therapy has been shown to improve symptoms of mood disorders and epilepsy, which leads to the hypothesis that the mechanism driving the benefits of yoga may work through stimulation of vagal efferents and an increase in GABA-mediated cortical-inhibitory tone.24,25
