Abstract Background: Weight change may influence breast cancer prognosis. The aim was to investigate whether weight change between the preoperative and 1-year postoperative visit was associated with risk of early breast cancer events in a population-based cohort of breast cancer patients in Sweden. Methods: Weight was measured by research nurses at the preoperative and the 1-year follow-up visits from 849 primary breast cancer patients operated between 2002 and 2011 in Lund, Sweden. Tumor characteristics, clinical data, and date of death were obtained from pathology reports, patient charts, and population registries. Results: The median follow-up was three years and 79 early breast cancer events occurred during the follow-up period. In all patients, there was a non-significant tendency towards decreased risk of early events with weight loss (Ptrend = 0.11). Weight loss was significantly associated with lower risk of early events compared to stable weight or weight gain in patients with axillary nodal involvement (Ptrend = 0.012), but not in patients without axillary nodal involvement. Further analysis showed that weight loss was only significantly associated with lower risk of early events among patients younger than 70 years with axillary nodal involvement, while patients who had gained more than 5% of the preoperative weight had significantly earlier events compared to those with stable weight. The results remained significant after adjustment for age at diagnosis, natural logarithm of the preoperative weight, invasive tumor size, axillary nodal involvement, and ER status. Further adjustments for smoking and alcohol abstinence, ever use of hormone therapy, or for treatments did not materially change the result. Conclusion: Weight loss was associated with significantly lower risk for early breast cancer events in patients younger than 70 years with axillary nodal involvement compared to stable weight or weight gain. If these results are confirmed, weight management may be incorporated in post-diagnosis management of breast cancer patients with axillary nodal involvement and have a significant beneficial impact on short-term prognosis. Citation Format: Xuyian Kenéz, Andrea Markkula, Maria Simonsson, Christian Ingvar, Carsten Rose, Helena C. Jernström. Weight change in relation to early breast cancer events in breast cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2171. doi:10.1158/1538-7445.AM2014-2171