Abstract 3722: Weight gain after a breast cancer diagnosis and breast cancer outcomes
Authors: Caan Bette J. , Kwan Marilyn L. , Weltzien Erin , Chen Wendy Y. , Pierce John P. , Nechuta Sarah , Lu Wei , Shu Xiao-ou 
Published: June 2012

Abstract
Introduction: Overweight or obesity measured around breast cancer diagnosis has been consistently associated with decreased survival, however the data on post diagnosis weight gain and survival is sparser and less consistent. We conducted a pooled investigation of weight gain and survival using data from the After Breast Cancer Pooling Project (ABC Pooling Project).
Methods: The ABC Pooling Project includes 18,336 breast cancer survivors from four prospective cohorts (three from the US and one from Shanghai, China) diagnosed between 1976 and 2006 with invasive primary breast cancer at ages 20-83 years. Delayed entry Cox proportional hazards models were used to estimate hazard ratios (HRs) and associated 95% confidence intervals (CIs) for the associations of weight gain with breast cancer death, death due to other causes and overall death, adjusted for age at diagnosis, race/ethnicity, menopausal status, hormone receptor status, stage, positive lymph nodes, smoking and treatment.
Results: Average weight gain between pre-diagnosis and 18-48 months post diagnosis across all 4 cohorts was 1.6 kg and ranged from 0.9 – 3.4kg across individual cohorts. Moderate weight gain (3- &lt;10 kg) was more common among women who had a BMI &lt;25 before diagnosis (31.8%) than among women with a BMI 25- &lt;30(25.1%) or &gt; 30(22.4%), while extreme weight gain (&gt; 10kg) was slightly more prevalent among those with BMI over 30 compared to other BMI groups (8.6% for BMI &gt;30 compared to 5.3% BMI &lt; 25). Extreme weight gain when compared to women who remained weight stable (within 3 kg of pre-diagnosis weight) was significantly related to both overall death (HR 1.30, CI 1.07-1.58), death due to causes other than breast cancer (HR 1.65; 95% CI 1.15-2.36) but not to breast cancer death (1.17; 95% CI 0.93-1.49). Effects of extreme weight gain on overall death were predominantly seen in women whose BMI pre-diagnosis was &lt; 25 (HR 1.48; 95% CI 1.09, 2.01), and in women who at study enrollment had no history of hypertension (HR 1.33; 95% CI 1.13, 1.71) or diabetes (HR 1.37 95% CI 1.10, 1.69). In contrast, effects of extreme weight gain on death due to causes other than breast cancer were seen predominantly in women whose pre-diagnosis BMI was between 25-30 and women who reported hypertension (HR 2.01; 95% CI 1.22-3.30) but not diabetes at baseline survey.
Conclusion: Moderate weight gain of up to 10kg after a breast cancer diagnosis is more common among women who are normal or underweight than among women who are overweight or obese and does not result in poorer survival. Extreme weight gain of greater than 10kg occurs in less than 10% of the breast cancer survivors, is more frequent in obese women, and is associated with poor outcomes. Continued research into understanding both those most at risk for extreme weight gain and those most at risk for poorer outcomes due to extreme weight gain is warranted.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3722. doi:10.1158/1538-7445.AM2011-3722