Sustained Weight Loss and Risk of Breast Cancer in Women 50 Years and Older

A Pooled Analysis of Prospective Data

Lauren R. Teras; Alpa V. Patel; Molin Wang; Shiaw-Shyuan Yaun; Kristin Anderson; Roderick Brathwaite; Bette J. Caan; Yu Chen; Avonne E. Connor; A. Heather Eliassen; Susan M. Gapstur; Mia M. Gaudet; Jeanine M. Genkinger; Graham G. Giles; I-Min Lee; Roger L. Milne; Kim Robien; Norie Sawada; Howard D. Sesso; Meir J. Stampfer; Rulla M. Tamimi; Cynthia A. Thomson; Shoichiro Tsugane; Kala Visvanathan; Walter C. Willett; Anne Zeleniuch-Jacquotte; Stephanie A. Smith-Warner

Disclosures

J Natl Cancer Inst. 2020;112(9):929-937. 

In This Article

Abstract and Introduction

Abstract

Background: Excess body weight is an established cause of postmenopausal breast cancer, but it is unknown if weight loss reduces risk.

Methods: Associations between weight change and risk of breast cancer were examined among women aged 50 years and older in the Pooling Project of Prospective Studies of Diet and Cancer. In 10 cohorts, weight assessed on three surveys was used to examine weight change patterns over approximately 10 years (interval 1 median = 5.2 years; interval 2 median = 4.0 years). Sustained weight loss was defined as no less than 2 kg lost in interval 1 that was not regained in interval 2. Among 180 885 women, 6930 invasive breast cancers were identified during follow-up.

Results: Compared with women with stable weight (±2 kg), women with sustained weight loss had a lower risk of breast cancer. This risk reduction was linear and specific to women not using postmenopausal hormones (>2–4.5 kg lost: hazard ratio [HR] = 0.82, 95% confidence interval [CI] = 0.70 to 0.96; >4.5–<9 kg lost: HR = 0.75, 95% CI = 0.63 to 0.90; ≥9 kg lost: HR = 0.68, 95% CI = 0.50 to 0.93). Women who lost at least 9 kg and gained back some (but not all) of it were also at a lower risk of breast cancer. Other patterns of weight loss and gain over the two intervals had a similar risk of breast cancer to women with stable weight.

Conclusions: These results suggest that sustained weight loss, even modest amounts, is associated with lower breast cancer risk for women aged 50 years and older. Breast cancer prevention may be a strong weight-loss motivator for the two-thirds of American women who are overweight or obese.

Introduction

In 2016, the World Health Organization estimated that 40% of women worldwide were overweight or obese.[1] In the United States, more than two of every three adult women were overweight or obese as of 2014.[2] Although high body mass index (BMI) is an established risk factor for postmenopausal breast cancer,[3,4] currently there is insufficient evidence to determine if the increased risk from excess body weight is reversible.[4] Given that breast cancer is the most commonly diagnosed cancer in women worldwide,[5] the question of whether weight loss can reduce breast cancer risk is of great public health importance.

Bariatric surgery studies suggest that weight loss may reduce breast cancer risk,[6–9] but results from studies of surgical weight loss may not be applicable to the general population. Bariatric surgery patients are a select group in that they undergo health screening before surgery, have an extremely high body weight before surgery, lose extremely large amounts of weight in a short period of time, and undergo hormonal and metabolic changes from the surgery that induce more pronounced biological responses than shown with the generally modest weight loss obtained through diet and exercise.[10] Results on weight loss and breast cancer from most population-based observational studies have been null but were limited by small numbers of women who lost weight.[3] Importantly, most of these studies did not assess sustained weight loss and focused on changes in body weight from early (aged 18–20 years, when women tended to be at their leanest) to middle or later (aged 40 years and older) adulthood. Results from three[11–13] of four[11–14] prospective studies that examined weight loss during middle or later adulthood suggested that weight loss during this time period may be associated with lower breast cancer risk. Furthermore, two[11,12] of the studies suggest that sustained weight loss is of particular importance for postmenopausal breast cancer risk. In these studies, however, weight loss was rare, particularly sustained weight loss, and sample size was extremely limited.

Using the Pooling Project of Prospective Studies of Diet and Cancer (DCPP), we set out to estimate the association of sustained weight loss in middle or later adulthood on subsequent breast cancer risk. This analysis includes more than 180 000 women aged 50 years and older from 10 prospective studies with three or more weight measures before breast cancer follow-up. Although some women from previously published reports[11,12,14] are included, this analysis is the first to be sufficiently powered to examine the important question of whether sustained weight loss can impact breast cancer risk.

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