Abstract 5758: Regular aspirin use, breast tumor characteristics and long-term breast cancer survival

Abstract Compelling epidemiologic data, supported by experimental evidence, suggest aspirin may improve survival in breast cancer patients. However, recent clinical trials showed a lack of protective effect, though length of intervention (18 months to 4.7 years) and follow-up (20 months to 4.7 years) were limited. We sought to examine the association between post-diagnostic aspirin use (frequency, dose, and duration), timing and age of initiation on breast cancer-specific mortality. Our study included 10,493 women diagnosed with stage I, II, or III invasive breast cancer. Participants were enrolled in the large, prospective Nurses’ Health Study (NHS) and NHSII in 1980 and 1989 prior to diagnosis and followed up through June 1, 2017. We collected information on frequency, dose and duration of aspirin use. Regular aspirin use was defined as using aspirin (standard- and low-dose) ≥2 days per week, and non-regular aspirin users were those who reported use of aspirin <2 days per week. We used Cox proportional hazard models to calculate multivariable adjusted hazard ratios (HRs) for breast cancer-specific mortality. After a median follow-up of 10 years, there were 2,506 total deaths and 1,221 breast cancer-specific deaths among 10,493 stage I to III breast cancer patients over 32 years of follow-up. In multivariable models, regular use of aspirin (n=3,523; 34%) was associated with a 38% lower risk of death from breast cancer compared with non-regular users (including nonusers) (HR=0.62, 95% CI: 0.54-0.71). The association was independent of pre-diagnostic aspirin use. Associations between aspirin use and breast cancer-specific mortality were stronger with longer time since diagnosis (HRs for <5 years since diagnosis: 0.73 (95% CI: 0.59-0.90), 5-<10 years: 0.63 (95% CI: 0.49-0.80), and ≥10 years: 0.53 (95% CI: 0.41-0.69)). The relations between aspirin use and breast cancer survival were similar across categories of dose (compared to non-users, HRs for 0.5-5 tablets per week: 0.59 (95% CI: 0.51-0.68); ≥6 tablets per week: 0.60 (95% CI: 0.48-0.74)) and appeared stronger with longer duration (compared to non-users, HRs for <5 years: 0.80 (95% CI: 0.57, 1.10); ≥5 years: 0.61 (95% CI: 0.51, 0.72)). For women who initiated regular aspirin use after age 70, regular aspirin use was associated with worse survival (HR=1.74, 95% CI: 1.16-2.63); on the other hand, initiation of regular aspirin use at age ≤60 (HR=0.72, 95% CI: 0.54-0.95) or 60-≤70 (HR=0.69, 95% CI: 0.50-0.95) was associated with improved survival (p-interaction=0.02). Regular aspirin use after diagnosis of nonmetastatic breast cancer was associated with improved long-term survival over 32 years. Although the associations between post-diagnostic regular aspirin use and improved survival did not differ by BMI, smoking or tumor characteristics, women who initiated regular aspirin use >70 years of age had increased risk of death due to breast cancer. Citation Format: Cheng Peng, Michelle D. Holmes, Wendy Y. Chen, Tengteng Wang, Kristen D. Brantley, Yujing Jan Heng, Pepper J. Schedin, Bernard A. Rosner, Walter C. Willett, Meir J. Stampfer, Rulla M. Tamimi, A. Heather Eliassen. Regular aspirin use, breast tumor characteristics and long-term breast cancer survival. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5758.