P1-08-18: Aspirin Exposure and Nodal Status at Diagnosis in Women with Stage I-III Breast Cancer.

Abstract

Abstract Background: The recent Nurses’ Health Study reported an association between aspirin use and a reduction in breast cancer (BC) recurrence and BC-specific mortality. It has been suggested based on preclinical data that these effects may be due to the inhibition of tumor invasion and metastasis by aspirin. To test this hypothesis we examined the association between aspirin exposure prior to BC diagnosis and nodal involvement at diagnosis. Methods: A retrospective analysis was conducted using linked pharmacy claims and cancer registry data from the National Cancer Registry Ireland. Women with an incident diagnosis of stage I-III BC between 2001–2006 and no prior invasive cancer were included. Women with a prescription for aspirin at any time in the year prior to diagnosis were defined as exposed. Multivariate logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for (a) N0 disease; (b) N1 disease (c) N1/2/3 disease at diagnosis in aspirin exposed (overall exposure & exposure quartiles by duration of use) versus unexposed women. All analyses were adjusted for age, tumor size/grade, ER, PR and HER2 receptor status. Analyses were repeated including women with stage IV BC at diagnosis. Survival analyses are ongoing. Results: 4212 women with stage I-III BC at diagnosis were identified. 1086 (25.8%) had a supply of aspirin available to them in the year prior to diagnosis (median dose 75mg, interquartile range 75mg, 75mg). Women taking aspirin were older than those who did not (74.3 yrs/64.4 yrs p<0.05). There was no difference in tumor sizes, grade, ER, PR or HER2 receptor status between exposed and unexposed women. In the multivariate logistic regression analysis aspirin exposure was associated with significantly increased odds of an N0 tumor (Table 1; OR 1.27 95%CI 1.09, 1.48) and significantly decreased odds of an N1 or N1/2/3 tumor. Additionally, women taking aspirin for >95% of the year prior to diagnosis had the highest odds of an N0 tumor (Table1; OR 1.50 95%CI 1.14, 1.97). There was no difference in the odds of an N0 tumor for women taking aspirin for <40% of the prior year (OR 1.01 95%CI 0.78, 1.31). Inclusion of stage IV BC (n=789) in the analysis did not significantly alter these results. Discussion: This study demonstrates a significant association between aspirin use in the year prior to BC diagnosis and the degree of nodal involvement at diagnosis. Furthermore there was a clear dose-response relationship between increasing duration of exposure and nodal status. These associations are unlikely to be due to confounding by healthy user/adherer behaviors as tumor sizes did not vary significantly between unexposed and exposed women, or across quartiles of exposure duration. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-08-18.