Abstract
Obesity has been well studied in relation to breast cancer survival. However, the associations of post-diagnosis obesity and late outcomes (≥5 years after diagnosis) have been much less studied. A total of 4062 5-year disease-free patients were recruited from the Shanghai Breast Cancer Survival Study, a longitudinal study of patients diagnosed during 2002-2006. Cox proportional hazard model with restricted cubic spline were used to evaluate the potential non-linear associations of post-diagnosis body mass index (BMI) and waist-to-hip ratio (WHR) with late all-cause mortality and late recurrence. While no significant association was observed for post-diagnosis BMI or WHR with late recurrence; a U-shaped association was observed for the two measures with late all-cause death. Women with BMI of 25.0 kg/m2 or WHR of 0.83 were at the lowest risk of late all-cause mortality, whereas those with BMI beyond the range of 22.1–28.7 kg/m2 or WHR beyond the range of 0.81–0.86 had a higher risk. ER, stage or menopausal status did not modify the effect of post-diagnosis BMI or WHR on the outcomes. In conclusion, post-diagnosis BMI and WHR, as indicators of overall and central obesity respectively, were associated with late all-cause mortality in U-shaped pattern among long-term breast cancer survivors.
Highlights
Body mass index (BMI) has been consistently associated with both all-cause mortality and recurrence in a U-shaped or J-shaped pattern[1,2,3,4,5,6]
In our previous report based on the Shanghai Breast Cancer Survival Study (SBCSS), we found that obesity (BMI > 30 kg/m2) measured at 6 months after diagnosis was inversely related to breast cancer prognosis after
No significant modifying effect was observed for age at diagnosis (
Summary
Body mass index (BMI) has been consistently associated with both all-cause mortality and recurrence in a U-shaped or J-shaped pattern[1,2,3,4,5,6]. Most studies[1, 2, 7,8,9], not all[3, 10] suggested that WHR was positively associated with breast cancer survival. Obesity (BMI ≥ 30 kg/m2) or severe obesity (BMI ≥ 35 kg/m2) post-diagnosis or at diagnosis were found in relation to higher hazard of all-cause death, breast cancer death and recurrence 5–10 years after diagnosis. In our previous report based on the Shanghai Breast Cancer Survival Study (SBCSS), we found that obesity (BMI > 30 kg/m2) measured at 6 months after diagnosis was inversely related to breast cancer prognosis after. We further followed up the cancer cases to explore the relationship of both indicators with late all-cause mortality and late recurrence, i.e. events occurring 5 years after diagnosis. In addition to using a traditional analysis method, which categorizes BMI and WHR according to World Health Organization standard[20] or quartile distributions, we applied Cox proportional hazard model with restricted cubic spline (RCS) to reveal the potential non-linearity associations of BMI and WHR with late outcomes
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