The science of hope.

Hope is a contextual term that has different connotations depending on the setting. We analyse the concept of hope with respect to its applicability for oncology. We review studies that present hope as a direct or secondary mediator of outcome. We posit that an individual's level of hope is often determined by innate personality characteristics and environmental factors, but can also be physiologically influenced by immune modulators, neurotransmitters, affective states, and even the underlying disease process of cancer. We argue that hope can be a therapeutic target and review evidence showing the effects of hope-enhancing therapies. Given the potential for hope to alter oncological outcomes in patients with cancer and the opportunity for improvement in quality of life, we suggest further research directions in this area.