Risk factors for the incidence of breast cancer: do they affect survival from the disease?

Risk factors that influence the incidence of breast cancer may also affect survival after diagnosis. Data from 4,560 women with invasive breast cancer who had taken part in the population-based Studies of Epidemiology and Risk Factors in Cancer Heredity (SEARCH) breast cancer study were used to investigate the influence on survival of variables related to pregnancy, menarche and menopause, prior use of exogenous hormones, height, weight, body mass index (BMI), smoking history, and alcohol intake. In univariate analyses, there was no association between prognosis and age at menarche and menopause, menopausal status at diagnosis, smoking history, or prior use of the oral contraceptive pill. Women whose most recent pregnancy was more than 30 years ago had a 35% reduced risk of dying (95% CI, 8% to 54%) compared with women who had a full-term pregnancy in the past 15 years, and the use of hormone replacement therapy for more than 4 years was associated with a similar risk reduction. BMI was associated with a 3% (95% CI, 1% to 4%) increase in mortality per unit increase. Improved prognosis was seen with increasing current alcohol consumption, with a 2% (95% CI, 1% to 3%) reduction in the risk of death per unit of alcohol consumed per week. The apparent benefit of alcohol intake has not been described before, and our data need to be interpreted with some caution. However, our finding that an increase in BMI is associated with a poorer prognosis supports previously published data and suggests that advice on weight loss should be given to all obese patients with breast cancer.