Abstract 732: Weight gain after age 18 and breast cancer risk: A meta-analysis

Abstract Introduction: Current cancer research recognizes that early life factors are important risk factors for breast cancer. Studies suggest that weight gain after age 18 plays a role in the development of breast cancer; however, the research related to their association is inconsistent. Thus, we performed a meta-analysis to evaluate the associations between weight gain after age 18 and risk of breast cancer and to clarify whether there is heterogeneity stratified by menopausal status. Methods: We performed a comprehensive literature search of all relevant studies published prior to February 19, 2021, according to the established inclusion criteria, utilizing Medline (Ovid), Embase, Scopus, Cochrane Library, and ClinicalTrials.gov. Two reviewers independently reviewed the articles for final inclusion. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of studies. Summary risk estimates (REs) with the corresponding 95% confidence intervals (CIs) were calculated using a random-effect or fixed-effect model, based on heterogeneity significance. Subgroup analyses were performed based on types of study design (case-control vs. cohort), country of study (the USA vs. other countries), and menopausal status (premenopausal vs. postmenopausal). We conducted sensitivity analysis and publication bias detection. We performed all statistical analyses with STATA version 16.1, and all P values were two-tailed, the test level was 0.05. Results: Seventeen out of 4,368 unique studies (12 case-control studies and 5 cohort studies) met the selection criteria. All studies were considered moderate to high quality with NOS scores that ranged from 5 to 8. Overall, weight gain after age 18 was associated with an increased risk of breast cancer (RE = 1.27; 95%CI = 1.13 - 1.42). In subgroup analyses, menopausal status was a source of heterogeneity. Weight gain after age 18 was associated with an increased risk of breast cancer among postmenopausal women (RE = 1.45; 95% CI = 1.31 - 1.62), but not among premenopausal women (RE = 1.03; 95% CI = 0.95 - 1.11). We did not find differences in associations by type of study design (case-control study: RE = 1.28; 95%CI = 1.09 - 1.51; cohort study: RE = 1.24; 95%CI = 1.07 - 1.44) nor country of study (the USA: RE = 1.28; 95%CI = 1.13 - 1.45; other countries: RE = 1.25; 95%CI = 0.94 - 1.66). The sensitivity analysis confirmed the stability of the results. The funnel plot suggested no publication bias. Conclusion: The current meta-analysis demonstrates that weight gain after age 18 is associated with increased breast cancer risk in postmenopausal women but not in premenopausal women. These findings suggest that it is important to keep weight within the healthy range and manage weight gain in adult life to fight against breast cancer among postmenopausal women. Citation Format: Yunan Han, Ebunoluwa E. Otegbeye, Carrie Stoll, Angela Hardi, Graham A. Colditz, Adetunji T. Toriola. Weight gain after age 18 and breast cancer risk: A meta-analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 732.