Abstract 4634: Breastfeeding and prognosis of breast cancer among Chinese women

Proceedings: AACR Annual Meeting 2020; April 27-28, 2020 and June 22-24, 2020; Philadelphia, PA Breastfeeding that linked to breast cancer risk may also influence the prognosis. A few previous studies on this topic have yielded inconsistent results. This study aimed to explore the dose-effect relationship between breastfeeding duration and breast cancer survival among Chinese women. We collected breastfeeding status, first breastfeeding duration (FBD), total breastfeeding duration (TBD) and average breastfeeding duration per child (ABD) from 3110 primary breast cancer patients recruited between October 2008 and June 2016 in Guangzhou, China and followed up until June 30, 2018. Restricted cubic splines and Cox proportional regression models were conducted to estimate the hazard ratios (HRs) and 95% confidence intervals (95% CI) for overall survival (OS) and progression-free survival (PFS) in association with breastfeeding. Long FBD (≥13 months) (HR=1.56 [1.13-2.17]), ABD (≥13 months) (HR=1.43 [1.04-1.96]) and TBD (≥37 months) (HR=1.73 [1.07-2.80]) were found to be associated with an increased risk of progression compared to moderate durations (FBD/ABD of 7-12 months, TBD of 19-36 months). Similar associations were observed for all-cause death. When stratified by ER status, the above effects of long FBD and ABD occurred only among patients with ER-positive tumor and the interactions were significant (FBD: Pinteraction=0.04 and 0.06, ABD: Pinteraction=0.07 and 0.04 for OS and PFS, respectively). Additionally, short FBD (≤6 months) increased the risk of a poor prognosis among young patients (≤45 years) (HR=1.86 [1.04-3.32] and 1.58 [1.06-2.34] for OS and PFS, respectively) but not old women (Pinteraction=0.02 for both OS and PFS). These findings would help clinical counseling and gaining insight into the mechanisms of breast cancer development. Citation Format: Zefang Ren, Xiang Wang, Luying Tang. Breastfeeding and prognosis of breast cancer among Chinese women [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4634.