Plain language summary
Literature shows that women with oestrogen-receptor-positive (ER+) [cells that have a receptor protein that binds the hormone oestrogen] breast cancer have a better prognosis in the first several years after diagnosis but may have higher risk of recurrence in later years after diagnosis. The aim of this study was to evaluate the associations of postdiagnosis lifestyle factors in association with breast cancer prognosis overall with ER+ late breast cancer outcomes among breast cancer survivors. This study is a prospective study based on ‘The After Breast Cancer Pooling Project’ which includes data from several long-term (>10 years), prospective cohorts of breast cancer survivors. This study included breast cancer survivors from the U.S. cohorts only i.e. a pooled analysis of over 6,500 ER+ breast cancer survivors. Results indicate that: • large post-diagnosis weight gain, obesity, and daily alcohol consumption (≥ 1 drink/day) increased the risk of late recurrence (≥5 years after diagnosis); • physical activity reduced the risk of all-cause mortality, but not the risk of late recurrence; and • current and heavy former smoking was associated with increased risk of late recurrence and all-cause mortality. Authors conclude that modifiable lifestyle factors were important predictors of late recurrence and mortality among long-term ER+ breast cancer survivors.
Abstract
Lifestyle factors have been well studied in relation to breast cancer prognosis overall; however, associations of lifestyle and late outcomes (>5 years after diagnosis) have been much less studied, and no studies have focused on estrogen receptor-positive (ER+) breast cancer survivors, who may have high risk of late recurrence and mortality. We utilized a large prospective pooling study to evaluate the associations of lifestyle factors with late recurrence and all-cause mortality among 6,295 5-year ER+ Stage I-III breast cancer survivors. Pooled and harmonized data were available on clinical factors and lifestyle factors (pre- to post-diagnosis weight change, body mass index (BMI) (kg/m(2)), recreational physical activity, alcohol intake and smoking history), measured on average 2.1 years after diagnosis. Updated information for weight only was available. Study heterogeneity was evaluated by the Q-statistic. Multivariable Cox regression models were stratified by study. Adjusting for clinical factors and potential confounders, ≥ 10% weight gain and obesity (BMI, 30-34.99 and ≥ 35) were associated with increased risk of late recurrence (hazard ratios (95% confidence intervals): 1.24 (1.00-1.53), 1.40 (1.05-1.86) and 1.41 (1.02-1.93), respectively). Daily alcohol intake was associated with late recurrence, 1.28 (1.01-1.62). Physical activity was inversely associated with late all-cause mortality (0.81 (0.71-0.93) and 0.71 (0.61-0.82) for 4.9 to <17.4 and ≥ 17.4 metabolic equivalent-hr/week). A U-shaped association was observed for late all-cause mortality and BMI using updated weight (1.42 (1.15-1.74) and 1.40 (1.09-1.81), <21.5 and ≥ 35, respectively). Smoking was associated with increased risk of late outcomes. In this large prospective pooling project, modifiable lifestyle factors were associated with late outcomes among long-term ER+ breast cancer survivors.
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