Abstract PD1-04: Association of aspirin and clinical outcomes in patients with invasive breast cancer
Authors: Li YR , Steel L , Carrigan E , Tchou J 
Published: May 2016

Long-term low-dose aspirin use has been observed to reduce the risk of colorectal, breast and other cancers. The most prominent effect has been in colorectal cancer, in which large-scale meta-analyses have shown that there is an approximately 20% relative risk reduction in participants who took aspirin for four or more years. The role of long-term NSAID use in breast cancer risk is less clear although preliminary observational case-control studies suggest an association between aspirin use and reduced incidence of hormone receptor-positive breast cancers though no clear evidence exists to support a clear mortality benefit among patients with a history of prior NSAID use as opposed to those who do not.

To investigate whether a history of aspirin use is associated with improved clinical outcome in breast cancer, we examined the pattern of aspirin use, cancer pathology and overall survival of over 1000 patients diagnosed with and treated for invasive breast cancer at our institution, for whom long-term follow up was available. A history of aspirin use for at least a period of 30 days prior to breast cancer diagnosis was reported in nearly 14% of individuals. Aspirin use was associated with being older than the age of 50 at diagnosis (79.8% vs 66.5%; Fisher's Exact Test (P &lt; 3.2x10-3) and being of African American race (49.1% vs 28.7%; P &lt; 3.4x10-2), when compared to those who have not used aspirin.

Aspirin use correlated with prognostic factors that are known to be associated with poor outcomes. They include axilla node positive disease (44.5% vs 27.0%, p&lt; 0.032), evidence of lymphovascular invasion (24.7% vs 15.4%, p&lt; 0.049), Her2-neu positive disease (&lt;0.0083). In contrast to prior retrospective case-control studies, no significant association between aspirin use and hormone receptor positive disease was noted for either ER (p=0.19) or PR(+) receptor status (p=0.12). Finally, we examined if aspirin use prior to breast cancer diagnosis has any impact on disease outcome. Over a median follow up of 60.0 months, univariate analysis using cox proportional hazard modeling demonstrated that the use of low-dose aspirin prior to the diagnosis of breast cancer was associated with an increased all-cause mortality when compared to patients without aspirin use prior to cancer diagnosis (HR=3.084, 95% CI=1.961 to 4.848). On multivariate analysis, we found that recent history of aspirin use was significantly associated with a worse overall survival (HR 2.65; 95%CI 1.37 -5.12, P &lt; 3.77 x 10-3), when controlled for other prognostic factors including receptor status, tumor size, tumor grade, number of positive regional lymph nodes, positive margins, as well as race and age at diagnosis.

This is the first study to report on the association of aspirin use with breast cancer outcomes in a large patient cohort treated at a single institution. Although aspirin in breast and cancers has been associated with reduced cancer incidence, a history of aspirin use prior to breast cancer diagnosis does not appear to be protective or associated with improve clinical outcomes or survival among breast cancer patients. Ongoing efforts are examining the mechanism underlying this association.

Citation Format: Li YR, Steel L, Carrigan E, Tchou J. Association of aspirin and clinical outcomes in patients with invasive breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr PD1-04.