Breast cancer and social environment: getting by with a little help from our friends.

Social environment is a well-recognized determinant in health and wellbeing. Among breast cancer patients, inadequate social support is associated with a substantial increase in cancer-related mortality. A common explanation is that socially isolated individuals fare worse due to reduced instrumental support (i.e., assistance meeting the demands of treatment). However, the ability to replicate the detrimental effects of social isolation on mammary tumor growth in rodents strongly suggests an alternative explanation; i.e., socially isolated individuals have a physiological milieu that promotes tumor growth. This review summarizes the clinical and basic science literature supporting social influences on breast cancer, and provides a conceptual physiological framework for these effects. We propose that social environment contributes to the vast individual differences in prognosis among breast cancer survivors because social environment is capable of altering basic physiological processes, which in turn can modulate tumor growth. Appreciation of the role of social environment in breast cancer progression could promote the identification of patients at increased risk for poor outcomes. In addition, characterization of the underlying physiological mechanisms could lead to targeted disruption of detrimental pathways that promote tumor progression in socially isolated individuals, or exploitation of protective pathways activated through social engagement as novel therapeutic complements to contemporary treatments.