Lifestyle factors and survival in women with breast cancer.

With increasing longevity and more effective cancer therapies, the population of cancer survivors is increasing. For example, it is estimated that there are over 2 million breast cancer survivors in the United States. Among cancer survivors and their families, there is substantial interest in whether there is anything that they can do beyond conventional therapy to improve their prognosis. Chief among these is interest in diet and use of complementary and alternative therapies. Despite this interest, there is surprisingly little that is known about the effects of these factors on cancer survival. This is in part because of the usual approach to research on diet and breast cancer in human populations. Studies that have had food and nutrition as a main interest have focused almost exclusively on cancer etiology and prevention; there are literally hundreds of such studies. Meanwhile, studies of populations after a breast cancer diagnosis have rarely considered lifestyle factors. Such studies have focused largely on therapeutics, such as effects of different chemotherapy regimens, or prognostic factors, such as the effects of stage of disease, hormone receptor status, or gene expression signatures on prognosis. To the extent that lifestyle factors have been a focus of cancer prognosis studies, they have often been aimed at the question of whether they impact quality of life, and not on whether they influence cancer survival or recurrence. There have been a handful of studies that have had lifestyle factors such as diet and physical activity as a principal focus. In addition to 2 randomized trials, the Women's Intervention Nutrition Study (WINS) and the Women's Healthy Eating and Living Study, there are at least 5 ongoing prospective cohort studies in breast cancer survivors that have diet as a main focus. Although these studies differ in various aspects, they are all aimed at examining whether differences in diet may result in differences in recurrence and mortality rates. One such study, the Pathways Study, is a prospective cohort study that began recruitment of study participants in early 2006. This study is unique in that it is enrolling women as soon after breast cancer diagnosis as is practical, whereas other studies have generally enrolled women after completion of adjuvant therapy or later. This and other studies promise to provide some of the first objective information regarding diet and breast cancer prognosis and serve as models for studies of diet and prognosis of other cancers.