Abstract 3225: Time since last birth in relation to breast cancer mortality
Authors: Zirpoli Gary R. , Castro-Webb Nelsy , Bertrand Kimberly A. , Palmer Julie R. 
Published: June 2022

Abstract
Women who develop breast cancer less than 10 years after giving birth have been shown to have a poorer prognosis than women with a longer time since their last birth. Only a few studies have examined this relation separately by molecular features of the tumor; two observed poorer outcomes for women with hormone receptor positive tumors. A better understanding of the relation between time since last birth and risk of recurrence and death could lead to targeted treatments and/or surveillance of young women who develop breast cancer within 10 years of giving birth. There has been little research on this topic among Black women, who have a higher incidence of breast cancer at young ages compared to White women. We assessed the relation of time since last birth to breast cancer mortality according to estrogen receptor (ER) status of the primary tumor among breast cancer patients who are participants in the prospective Black Women’s Health Study (BWHS).
The BWHS includes 59,000 U.S. Black women who enrolled in the study in 1995 and have been followed by biennial questionnaire since then. The present analysis was restricted to parous women diagnosed before age 50 (N=658) because older patients would have been unlikely to have given birth within the past 10 years. ER status was positive for 348 cases, negative for 199, and unknown for 111. Follow-up time was from time of diagnosis to death or the end of 2018, whichever came first. Cox regression analysis, adjusted for age and stage at diagnosis, was used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for breast cancer specific death for women diagnosed &lt;10 years since last birth relative to women diagnosed ≥10 years since last birth.
The median age at diagnosis was 44, with 41% of cancers diagnosed at stage I, 43% at stage II, and 16% at stage III. About a third (31%) had given birth &lt10 years before diagnosis. During follow-up, there were 159 total deaths, 132 of which were due to breast cancer. Among women diagnosed with ER-positive breast cancer, the HR for breast cancer death for women who gave birth &lt10 years prior to diagnosis relative to women who had not had a recent birth was 2.45 (95% 1.07-5.58). The association was even stronger among women who survived the first five years, with an HR of 3.38 (95% CI 1.34-8.51). Time since last birth was not associated with ER-negative breast cancer mortality (HR 1.06, 95% CI 0.46-2.46).
Late recurrences are a particular problem with ER-positive breast cancer. The present findings suggest a relatively short interval (e.g., &lt10 years) between childbirth and a breast cancer diagnosis may increase risk of a late recurrence and death from ER-positive breast cancer. Greater awareness of this association may lead to improved surveillance of survivors of early-onset breast cancer.
Citation Format: Gary R. Zirpoli, Nelsy Castro-Webb, Kimberly A. Bertrand, Julie R. Palmer. Time since last birth in relation to breast cancer mortality [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 3225.