Host factors and cancer progression: biobehavioral signaling pathways and interventions.

Whereas evidence for the role of psychosocial factors in cancer initiation has been equivocal, support continues to grow for links between psychological factors such as stress, depression, and social isolation and progression of cancer. In vitro, in vivo, and clinical studies show that stress- related processes can impact pathways implicated in cancer progression, including immuno-regulation, angiogenesis, and invasion. Contributions of systemic factors, such as stress hormones to the crosstalk between tumor and stromal cells, appear to be critical in modulating downstream signaling pathways with important implications for disease progression. Inflammatory pathways may also be implicated in fatigue and other factors related to quality of life. Although substantial evidence supports a positive effect of psychosocial interventions on quality of life in cancer, the clinical evidence for efficacy of stress-modulating psychosocial interventions in slowing cancer progression remains inconclusive, and the biobehavioral mechanisms that might explain such effects are still being established. This article reviews research findings to date and outlines future avenues of research in this area.