Purpose: The associations between use of aspirin, other nonsteroidal anti-inflammatory drugs (NSAIDs), and acetaminophen and breast cancer incidence in postmenopausal women are uncertain. We examined these associations with breast cancer, both overall and by molecular subtype.
Patients and methods: We observed 84,602 postmenopausal women, free of cancer in 1980, until June 2008 and prospectively collected data on analgesic use, reproductive history, and other lifestyle factors using biennial questionnaires. Proportional hazards models were used to estimate multivariable relative risks (RRs) and 95% CIs.
Results: We documented 4,734 cases of incident invasive breast cancer. Compared with nonuse of aspirin, multivariable RRs of regular aspirin use (≥ two tablets per week) for more than 20 years were 0.91 for overall breast cancer (95% CI, 0.81 to 1.01; P(trend) = 0.16), 0.90 for estrogen receptor (ER) -positive progesterone receptor (PR) -positive breast cancer (95% CI, 0.77 to 1.06; P(trend) = 0.17), and 0.91 for ER-negative PR-negative breast cancer (95% CI, 0.68 to 1.22; P(trend) = 0.97). Results did not vary appreciably by past or current use, days per week of use, or dosage of use. Use of other NSAIDs and acetaminophen was largely not significantly associated with breast cancer risk. Additionally, use of higher doses of each analgesic (≥ six tablets per week) for more than 10 years was generally not significantly associated with risk of breast cancer, either overall or by subtype. Furthermore, largely no substantial associations were noted for breast cancer molecular subtypes, including luminal A, luminal B, triple negative, basal-like, human epidermal growth factor receptor 2 positive, cyclooxygenase-2 (COX-2) negative, and COX-2 positive.
Conclusion: Our study suggests that use of aspirin, other NSAIDs, and acetaminophen is not importantly associated with risk of postmenopausal breast cancer, either overall or by specific subtype.