P4-12-03: Post-Diagnosis Weight Gain in Breast Cancer Survivors: When Should We Intervene?

Abstract

Abstract Significance. Weight gain after breast cancer diagnosis is common and has been linked to poor prognosis. Studies of the etiology and longitudinal pattern of post-diagnosis weight gain are limited, yet are critical to developing effective prevention strategies to enhance ***survival.. Approach. We investigated the longitudinal pattern and determinants of post-diagnosis weight gain among 1,436 breast cancer survivors. The population-based cohort included women newly diagnosed with a first primary in situ or invasive breast cancer. Subjects were interviewed within 6 months of diagnosis and again 5 years later to ascertain factors related to survival, including self-reported anthropometric measures. We employed: adjusted random effects linear regression to identify factors related to weight change during the follow-up; multiple imputation to account for missing data; and Wald tests to test for significance of interactions with follow-up time. Results. Average weight gain was 0.74 kilograms (kg) during the first year after diagnosis and 2.39 kg at the follow-up interview. The strongest predictors of post-diagnosis gain were body size characteristics before diagnosis, which varied with time since diagnosis. Compared to women with body mass index (BMI, kg/m2) 18.5−24.9 1 year before diagnosis, those with greater BMI were more likely to gain weight during the first year after diagnosis [difference in mean yearly increase: BMI 25.0−29.9 vs. 18.5−24.9 (95% confidence interval): 1.93 kg/year (0.50, 3.37); BMI >=30.0 vs. 18.5−24.9: 0.47 kg/year (0.24, 0.71)] and after the first year [5.17 kg/year (3.68, 6.66) and 0.93 kg/year (0.58, 1.28), respectively], with the effect greater during the first year (p-interaction: <0.001). A pre-diagnosis weight gain of more than 10% since age 20 was also associated with post-diagnosis weight gain [during year 1, difference in mean yearly increase compared to maintenance within 3% age 20 weight: 2.32 kg/year (0.59, 4.05); after year 1: 0.53 kg/year (0.17, 0.89)] with the effect again stronger during the first year (p-interaction: 0.02). Modest associations, which varied only slightly with time, included: increases in post-diagnosis weight gain with chemotherapy, tumor characteristics indicative of poor prognosis, and a previous diagnosis of hypertension, blood clots, or diabetes; and decreases with increasing recreational physical activity and a history of myocardial infarction. Conclusions. Greater pre-diagnosis BMI and pre-diagnosis adult weight gain are strongly related to post-diagnosis weight gain among breast cancer survivors. The rate of post-diagnosis weight gain appears to be faster during the first year than after, suggesting that interventions to prevent post-diagnosis weight gain may be most important during the first year after diagnosis, especially among women who with BMI >= 25.0 1 year prior to diagnosis. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-12-03.