Prospective study of regular aspirin use and the risk of breast cancer

Association between WHO First-Step Analgesic Use and Risk of Breast Cancer in Women of Working Age

We assessed the association between breast cancer and analgesic use in women of a specific working-age group. The Korean National Health Insurance Service-National Sample Cohort database (KNHIS-NSC) data were analyzed. We calculated hazard ratios (HRs) with 95% confidence intervals (CIs) for patients' cancer risk based on whether the women participated in economic activity (PEA or not PEA (NPEA) groups) and analgesic use. Additionally, breast cancer incidence variations by age group, and PEA or NPEAs, health behavior, Charlson Comorbidity Index, and analgesic use were evaluated. The PEA group had a higher cancer risk than the NPEA group (HR = 1.542, 95% CI: 1.345-1.768, p < 0.001). Breast cancer risk was high in the PEA, high income, and no history of exercise groups, but significantly reduced in the regular-use-of-analgesics group. Notably, the working age group of 40~49 years, within the PEA group, had the highest HR of breast cancer development (HR = 1.700, 95% CI = 1.361-2.124, p < 0.001); whereas regular analgesic use in those aged 25~39 years decreased breast cancer risk (HR = 0.611, 95% CI = 0.427-0.875, p < 0.05). In conclusion, our results suggest that individuals at a high-risk of comorbidity may benefit from regular use of analgesics, which may prove to be a useful strategy for breast cancer prevention in the Young-aged group.

Aspirin Use and Risk of Breast Cancer: A Meta-analysis of Observational Studies from 1989 to 2019

BACKGROUND

Some evidence shows that aspirin can reduce the morbidity and mortality of different cancers, including breast cancer. Aspirin has become a new focus of cancer prevention and treatment research at present, however, clinical studies found conflicting conclusions of its anticancer characteristics.

MATERIALS AND METHODS

A systematic literature search was performed in 8 electronic databases. The pooled relative risk (RR) with 95% confidence interval (CI) was calculated using the random effects model to estimate the effect of aspirin on breast cancer.

RESULTS

Forty-two published articles with 99,769 patients were identified. The meta-analysis showed a significant decrease in breast cancer risk with aspirin use (RR, 0.92; 95% CI, 0.89-0.96; I² = 72%). Aspirin use decreased the risk of hormone receptor-positive tumors (estrogen receptor [ER]-positive RR, 0.89; 95% CI, 0.82-0.97; I²=54%; progesterone receptor [PR]-positive RR, 0.86; 95% CI, 0.78-0.95; I²=32%; ER- and PR-positive RR, 0.92; 95% CI, 0.85-1.00; I²=45%) and reduced the risk of breast cancer in postmenopausal women (RR, 0.92; 95% CI, 0.86-0.98; I²=59%). Further analysis showed that for the in situ breast cancer, regular-dose and more than 3 years use of aspirin were associated with the reduced risk of breast cancer.

CONCLUSION

This meta-analysis suggested that aspirin may reduce the overall risk of breast cancer, reduce the risk of breast cancer in postmenopausal women, hormone receptor-positive tumors, and in situ breast cancer. Larger, multicenter clinical studies are needed to find the optimal dose range, frequency, and duration of the aspirin use to explore the best benefit-risk ratio.

Use of nonsteroidal anti-inflammatory drugs and breast cancer risk in a prospective cohort of postmenopausal women

BACKGROUND

Although anti-inflammatory agents could theoretically have anticancer properties, results from cohort studies on nonsteroidal anti-inflammatory drugs (NSAIDs) and breast cancer (BC) risk are inconsistent.

METHODS

We investigated the association between NSAID use and BC incidence in the French E3N prospective cohort, which includes 98,995 women born between 1925 and 1950 and insured by a health insurance plan that covers mostly teachers. Self-reported information on lifestyle and medical history has been collected biennially by questionnaires and matched with data from a drug reimbursement database covering the period 2004-2014. Women who self-reported current NSAID use in the 2000 or 2002 questionnaires or with at least two reimbursements in any previous 3-month period were defined as exposed to NSAIDs. Multivariable Cox regression models were used to estimate hazard ratios (HRs) for the association of NSAID use with BC risk.

RESULTS

In the current analysis, 62,512 postmenopausal women were followed between 2004 and 2014 (9 years on average, starting at a mean age of 63 years; 2864 incident BC). In multivariable models, there was no statistically significant association between NSAID use and BC risk [HR = 1.00 (0.92-1.08), compared with non-exposed women]. The NSAID-BC associations did not differ by NSAID types, BC subtypes, risk factors, and comorbidities, nor by duration and dose of use. However, a statistically significant interaction was observed by proton pump inhibitor (PPI) drug use (Pinteraction = 0.01) whereby a decreased risk of BC with NSAID use was only observed among women who also used PPI before.

CONCLUSION

Only women who used NSAIDs after having used PPI had a lower risk of BC. This result is novel and requires replication in other studies.

Aspirin might reduce the incidence of breast cancer: An updated meta-analysis of 38 observational studies

BACKGROUND

Many epidemiologic studies were performed to clarify the protective effect of regular aspirin use on breast cancer risks, but the results remain inconsistent. Here, we conducted an updated meta-analysis of 38 studies to quantitatively assess the association of regular aspirin use with risk of breast cancer.

METHOD

We performed a bibliographic database search in PubMed, Embase, Web of Science, Cochrane library, Scopus, and Google Scholar from January 1939 to December 2019. Relative risk (RR) estimates were extracted from eligible case-control and cohort studies and pooled using a random effects model. Subgroup analysis was conducted based on study design, aspirin exposure assessment, hormone receptor status, menopausal status, cancer stage as well as aspirin use duration or frequency. Furthermore, sensitivity and publication bias analyses were performed.

RESULTS

Thirty eight studies of 1,926,742 participants involving 97,099 breast cancer cases contributed to this meta-analysis. Compared with nonusers, the aspirin users had a reduced risk of breast cancer (RR = 0.91, 95% confidence interval [CI]: 0.87-0.95, P value of significance [Psig] < .001) with heterogeneity (P value of heterogeneity [Phet] < .001, I = 82.6%). Subgroup analysis revealed a reduced risk in case-control studies (RR = 0.83, 95% CI: 0.78-0.89, Psig < .001), in hormone receptor positive tumors (RR = 0.91, 95% CI: 0.88-0.94, Psig < .001), in situ breast tumors (RR = 0.79, 95% CI: 0.71-0.88, Psig < .001), and in postmenopausal women (RR = 0.89, 95% CI: 0.83-0.96, Psig = .002). Furthermore, participants who use aspirin for >4 times/wk (RR = 0.88, 95% CI: 0.82-0.96, Psig = .003) or for >10 years (RR = 0.94, 95% CI: 0.89-0.99, Psig = .025) appeared to benefit more from the reduction in breast cancer caused by aspirin.

CONCLUSIONS

Our study suggested that aspirin use might be associated with a reduced risk of breast cancer, particularly for reducing the risk of hormone receptor positive tumors or in situ breast tumors, and the risk of breast cancer in postmenopausal women.

Influence of Fibroblasts on Mammary Gland Development, Breast Cancer Microenvironment Remodeling, and Cancer Cell Dissemination

The stromal microenvironment regulates mammary gland development and tumorigenesis. In normal mammary glands, the stromal microenvironment encompasses the ducts and contains fibroblasts, the main regulators of branching morphogenesis. Understanding the way fibroblast signaling pathways regulate mammary gland development may offer insights into the mechanisms of breast cancer (BC) biology. In fact, the unregulated mammary fibroblast signaling pathways, associated with alterations in extracellular matrix (ECM) remodeling and branching morphogenesis, drive breast cancer microenvironment (BCM) remodeling and cancer growth. The BCM comprises a very heterogeneous tissue containing non-cancer stromal cells, namely, breast cancer-associated fibroblasts (BCAFs), which represent most of the tumor mass. Moreover, the different components of the BCM highly interact with cancer cells, thereby generating a tightly intertwined network. In particular, BC cells activate recruited normal fibroblasts in BCAFs, which, in turn, promote BCM remodeling and metastasis. Thus, comparing the roles of normal fibroblasts and BCAFs in the physiological and metastatic processes, could provide a deeper understanding of the signaling pathways regulating BC dissemination. Here, we review the latest literature describing the structure of the mammary gland and the BCM and summarize the influence of epithelial-mesenchymal transition (EpMT) and autophagy in BC dissemination. Finally, we discuss the roles of fibroblasts and BCAFs in mammary gland development and BCM remodeling, respectively.

Growth inhibitory effects of PC-NSAIDs on human breast cancer subtypes in cell culture

The potential role of non-steroidal anti-inflammatory drug (NSAID) therapy in the prevention and treatment of cancer has generated considerable research interest. Phosphatidylcholine (PC)-associated NSAIDs decrease the gastrointestinal side effects of NSAID therapy, and may be more effective than traditional NSAIDs in limiting tumor growth. In the present study, human cells representing three major breast cancer subtypes were cultured with aspirin, indomethacin and PC-associated forms of each drug, with PC alone as a control. All tested drugs decreased the tumor cell number after 8 days of culture, with PC-NSAIDs having the greatest inhibitory effect, and NSAIDs alone, particularly aspirin, having the least effect. PC alone was effective in limiting the proliferation of all cell lines, suggesting that the two components of PC-NSAIDs have an additive effect. The ELISA results did not support a strong role for inhibition of cyclooxygenase enzymes in the decrease in cancer cell proliferation, which may account for the limited effectiveness of aspirin alone. PC-NSAIDs, particularly indomethacin-PC, are attractive candidate drugs in the prevention and treatment of different types of breast cancer, including triple negative breast cancer.

Nonsteroidal anti-inflammatory drug use and breast cancer risk in a European prospective cohort study

Experimental studies have shown a protective effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on breast cancer development. However, results from epidemiological cohort studies are less consistent. Our objective was to assess the association between NSAID use and breast cancer risk within the European Prospective Investigation into Cancer and Nutrition (EPIC). EPIC is a prospective cohort study initiated in 1992 in 10 European countries. Self-reported information on NSAID use at baseline has been collected in five EPIC countries. Multivariable Cox regression models were used to estimate hazard ratios for the association of NSAID use with breast cancer incidence with adjustment for potential confounders. We also assessed effect modification by breast cancer risk factors and examined the associations within specific breast cancer subtypes. Among the 140,981 women included in the analysis, 7% were regularly using NSAIDs at baseline. During a median follow-up time period of 13 years, 7,379 incident breast cancer cases were diagnosed (816 in situ and 6,563 invasive). There were no statistically significant associations between NSAID use and breast cancer risk, overall and by subtypes. However, a statistically significant interaction was observed for invasive cases between NSAID use and ever use of menopausal hormonal therapy (MHT) among postmenopausal women [MHT users: HRNSAID use  = 0.84 (0.73-0.96); non MHT users: HRNSAID use  = 1.08 (0.93-1.25); pinteraction  = 0.05]. Our results indicate potential effect modification of MHT use on the association between use of NSAIDs and breast cancer risk which deserves in-depth investigation in studies with accurate data on both NSAID and MHT use.

Cardiovascular Disease and Breast Cancer: Where These Entities Intersect: A Scientific Statement From the American Heart Association

Cardiovascular disease (CVD) remains the leading cause of mortality in women, yet many people perceive breast cancer to be the number one threat to women's health. CVD and breast cancer have several overlapping risk factors, such as obesity and smoking. Additionally, current breast cancer treatments can have a negative impact on cardiovascular health (eg, left ventricular dysfunction, accelerated CVD), and for women with pre-existing CVD, this might influence cancer treatment decisions by both the patient and the provider. Improvements in early detection and treatment of breast cancer have led to an increasing number of breast cancer survivors who are at risk of long-term cardiac complications from cancer treatments. For older women, CVD poses a greater mortality threat than breast cancer itself. This is the first scientific statement from the American Heart Association on CVD and breast cancer. This document will provide a comprehensive overview of the prevalence of these diseases, shared risk factors, the cardiotoxic effects of therapy, and the prevention and treatment of CVD in breast cancer patients.

Evidence for Detection Bias by Medication Use in a Cohort Study of Breast Cancer Survivors

In previous studies, we found modestly decreased and increased risks of second breast cancer events with the use of statins and antibiotics, respectively, after adjustment for surveillance mammography. We evaluated detection bias by comparing receipt of surveillance mammography among users of these 2 disparate classes of medication. Adult women diagnosed with early-stage breast cancer during 1990-2008 (n = 3,965) while enrolled in an integrated health-care plan (Group Health Cooperative; Washington State) were followed for up to 10 years in the Commonly Used Medications and Breast Cancer Outcomes (COMBO) Study. Categories of antibiotic use included infrequent (1-3 dispensings/12 months) and frequent (≥4 dispensings/12 months) use, and categories of statin use included less adherent (1 dispensing/6 months) and adherent (≥2 dispensings/6 months). We examined associations between medication use and surveillance mammography using multivariable generalized estimating equations and evaluated the impact of adjusting for surveillance within Cox proportional hazard models. Frequent antibiotic users were less likely to receive surveillance mammography (odds ratio (OR) = 0.90, 95% confidence interval (CI): 0.82, 0.99) than were nonusers; no association was found among infrequent users (OR = 0.96, 95% CI: 0.90, 1.03). Adherent statin use was associated with more surveillance compared with nonuse (OR = 1.11, 95% CI: 1.01, 1.25), but less adherent statin use was not (OR = 1.03, 95% CI: 0.81, 1.31). No difference in associations between medications of interest and second breast cancer events was observed when surveillance was removed from otherwise adjusted models. The influence of detection bias by medication use warrants further exploration.

The Role of NSAIDs in Breast Cancer Prevention and Relapse: Current Evidence and Future Perspectives

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) have received considerable interest as potential chemopreventive agents. The aim of this review is to summarize the accumulated knowledge on the effect of NSAIDs on breast cancer incidence and natural history, and the underlying pathophysiology. NSAIDs mainly block inflammation by inhibiting cyclooxygenase enzymes, leading to lower prostaglandin synthesis. The latter has been reported to affect breast cancer risk through hormonal and inflammation-related pathways. Intensity, dose, frequency, duration, and timing of administration may also be significant. There is currently enough evidence to support a role of NSAIDs in breast cancer prevention and relapse, which deserves further large-scale experimental and clinical investigation.

Cyclooxygenase-2 Expression in Normal and Neoplastic Canine Mammary Cell Lines

Mammary cancer is the most common cancer in female dogs. Induction of cyclooxygenase-2 (COX-2), a key enzyme in prostaglandins (PGs) biosynthesis, has been demonstrated in various cancers in humans and dogs, including mammary cancer. The objective of this study was to investigate the expression and regulation of COX-2 in canine mammary epithelial cells. Cell lines derived from normal and neoplastic canine mammary glands were cultured in the absence or presence of phorbol 12-myristate 13-acetate (PMA), and immunoblots, immunocytochemistry, radioimmunoassays, and a cell proliferation assay were used to study COX-2 expression and PGs production. Results showed that the neoplastic cell line CMT12 constitutively overexpressed COX-2 protein whereas other mammary cell lines expressed low to undetectable basal levels of COX-2 protein. Basal PGE2 production was significantly higher ( P < .05) in CMT12 compared to other cell lines. Levels of COX-2 protein in CMT12 decreased in a time-dependent manner with serum starvation, and PMA stimulation induced a strong time-dependent increase in COX-2 protein. Treatment of CMT12 cells with NS-398 (a specific COX-2 inhibitor) significantly blocked PGE2 synthesis and reduced cell proliferation ( P < .05). These results indicate that some neoplastic canine mammary cell lines constitutively overexpress COX-2, and that COX-2 inhibition decreases PGE2 production and cell proliferation, supporting a role for COX-2 and PGs in canine mammary oncogenesis.

Personalizing Aspirin Use for Targeted Breast Cancer Chemoprevention in Postmenopausal Women

OBJECTIVE

To evaluate the association of aspirin and other nonsteroidal anti-inflammatory drugs with the incidence of postmenopausal breast cancer for risk subgroups defined by selected nonmodifiable or difficult to modify breast cancer risk factors in order to better understand the potential risk-benefit ratio for targeted chemoprevention.

PATIENTS AND METHODS

Postmenopausal women with no history of cancer on July 1, 1992 (N=26,580), were prospectively followed up through December 31, 2005, for breast cancer incidence (N=1581). Risk subgroups were defined on the basis of family history of breast cancer, age at menarche, age at menopause, parity/age at first live birth, personal history of benign breast disease, and body mass index. Hazard ratios (HRs) and 95% CIs adjusted for other breast cancer risk factors were estimated using Cox models.

RESULTS

Aspirin use was associated with a lower incidence of breast cancer for women with a family history of breast cancer (HR, 0.62 for 6 or more times per week vs never use; 95% CI, 0.41-0.93) and those with a personal history of benign breast disease (HR, 0.69; 95% CI, 0.50-0.95) but not for women in higher-risk subgroups for age at menarche, age at menopause, parity/age at first live birth, or body mass index. In contrast, inverse associations with aspirin use were observed in all lower-risk subgroups. Nonsteroidal anti-inflammatory drug use had no association with breast cancer incidence.

CONCLUSION

On the basis of their increased risk of breast cancer, postmenopausal women with a family history of breast cancer or a personal history of benign breast disease could potentially be targeted for aspirin chemoprevention studies. Future studies are needed to confirm these findings.

COX-2 inhibitors: a novel strategy in the management of breast cancer

Cyclooxygenase-2 (COX-2) inhibitors are common anti-inflammatory drugs with pleiotropic, endogenous actions that could be useful in the management of breast cancer. Here, we provide a complete understanding of the biochemistry of COX-2 and discuss the various molecular mechanisms behind its increased expression in breast cancer. We also analyze the possible mechanisms responsible for the anticancer effect of COX-2 inhibitors and provide an overview of the available preclinical and clinical data on the use of COX-2 inhibitors in breast cancer. Finally, we describe a mathematical model of the relation between the structure and biological potency of promising new COX-2 inhibitors (trans-stilbenes) using a 2D quantitative structure-activity relationship (QSAR) technique.

A window-of-opportunity biomarker study of etodolac in resectable breast cancer

Observational data show that nonsteroidal anti-inflammatory drug (NSAID) use is associated with a lower rate of breast cancer. We evaluated the effect of etodolac, an FDA-approved NSAID reported to inhibit cyclooxygenase (COX) enzymes and the retinoid X receptor alpha (RXR), on rationally identified potential biomarkers in breast cancer. Patients with resectable breast cancer planned for initial management with surgical resection were enrolled and took 400 mg of etodolac twice daily prior to surgery. Protein and gene expression levels for genes related to COX-2 and RXRα were evaluated in tumor samples from before and after etodolac exposure. Thirty subjects received etodolac and 17 subjects were assayed as contemporaneous or opportunistic controls. After etodolac exposure mean cyclin D1 protein levels, assayed by immunohistochemistry, decreased (P = 0.03). Notably, pre- versus post cyclin D1 gene expression change went from positive to negative with greater duration of etodolac exposure (r = −0.64, P = 0.01). Additionally, etodolac exposure was associated with a significant increase in COX-2 gene expression levels (fold change: 3.25 [95% CI: 1.9, 5.55]) and a trend toward increased β-catenin expression (fold change: 2.03 [95% CI: 0.93, 4.47]). In resectable breast cancer relatively brief exposure to the NSAID etodolac was associated with reduced cyclin D1 protein levels. Effect was also observed on cyclin D1 gene expression with decreasing levels with longer durations of drug exposure. Increased COX-2 gene expression was seen, possibly due to compensatory feedback. These data highlight the utility of even small clinical trials with access to biospecimens for pharmacodynamic studies.

Expression of Prostacyclin-Synthase in Human Breast Cancer: Negative Prognostic Factor and Protection against Cell Death In Vitro

Endogenously formed prostacyclin (PGI2) and synthetic PGI2 analogues have recently been shown to regulate cell survival in various cell lines. To elucidate the significance of PGI2 in human breast cancer, we performed immunohistochemistry to analyze expression of prostacyclin-synthase (PGIS) in 248 human breast cancer specimens obtained from surgical pathology files. We examined patients' 10-year survival retrospectively by sending a questionnaire to their general practitioners and performed univariate analysis to determine whether PGIS expression correlated with patient survival. Lastly, the effects of PGI2 and its analogues on cell death were examined in a human breast cancer cell line (MCF-7) and a human T-cell leukemia cell line (CCRF-CEM). PGIS expression was observed in tumor cells in 48.7% of samples and was associated with a statistically significant reduction in 10-year survival (P = 0.038; n = 193). Transient transfection of PGIS into MCF-7 cells exposed to sulindac increased cell viability by 50% and exposure to carbaprostacyclin protected against sulindac sulfone induced apoptosis in CCRF-CEM cells. Expression of PGIS is correlated with a reduced patient survival and protects against cell death in vitro, suggesting that PGIS is a potential therapeutic target in breast cancer.

Recent prediagnostic aspirin use, lymph node involvement, and 5-year mortality in women with stage I-III breast cancer: a nationwide population-based cohort study

Lymph node-positive breast tumors are more likely to express COX2 than node-negative tumors. In preclinical studies, COX2 inhibition prevents breast tumor spread to lymph nodes. Therefore, we examined the association between recent (1 year) prediagnostic use of aspirin (COX1/COX2 inhibitor), lymph node involvement at breast cancer diagnosis, and breast cancer-specific mortality. Women with stage I-III breast cancer diagnosed from 2001 to 2006 (N = 2,796) were identified from Ireland's National Cancer Registry. These data were linked to prescription refill and mammographic screening databases. Relative risks (RR) were estimated for associations between prediagnostic aspirin use and lymph node-positive status at diagnosis. HRs were estimated for associations between pre- and postdiagnostic aspirin use and 5-year mortality, stratified by lymph node status. Women with prediagnostic aspirin use were statistically significantly less likely to present with a lymph node-positive tumor than nonusers [RR = 0.89; 95% confidence interval (CI), 0.81-0.97], particularly those with larger (Pinteraction = 0.036), progesterone receptor (PR)-negative (Pinteraction < 0.001) or estrogen receptor (ER)-negative (Pinteraction = 0.056) tumors. The magnitude of this association increased with dose (Ptrend < 0.01) and dosing intensity (Ptrend < 0.001) and was similar in women with or without screen-detected tumors (Pinteraction = 0.70). Prediagnostic aspirin use was associated with lower 5-year breast cancer-specific mortality among women with lymph node-negative tumors (HR, 0.55; 95% CI, 0.33-0.92) but not node-positive tumors (HR, 0.91; 95% CI, 0.37-1.22). Tests for effect-modification were, however, not statistically significant (Pinteraction = 0.087). Postdiagnostic aspirin use was not associated with breast cancer-specific mortality (HR, 0.99; 95% CI, 0.68-1.45). Our findings indicate that recent prediagnostic aspirin use is protective against lymph node-positive breast cancer. This is a plausible explanation for reductions in breast cancer mortality reported in observational studies of aspirin use.

Effect of COX-2 inhibitors and other non-steroidal inflammatory drugs on breast cancer risk: a meta-analysis

Evidence on non-steroidal anti-inflammatory drugs (NSAID) use and breast cancer risk shows a slightly protective effect of these drugs, but previous studies lack randomized clinical trial results and present high heterogeneity in exposure measurement. This systematic review and meta-analysis widens the knowledge about NSAID use and breast cancer risk, updating the information from the last meta-analysis, focusing on evidence on specific effects of COX-2 inhibitors and differential expression patterns of hormonal receptors. A PubMed-database search was conducted to include all entries published with the keywords "BREAST CANCER NSAID ANTI-INFLAMMATORY" until 10/24/2013 providing original results from cohort studies, case-control studies, or randomized clinical trials with at least one reported relative risk (RR) or odds ratio (OR) on the association between any NSAID use and incidence of invasive breast cancer. This resulted in 49 publications, from which the information was retrieved about type of study, exposure characteristics, breast cancer characteristics, and breast cancer-NSAID association. Meta-analyses were performed separately for case-control and cohort studies and for different hormone-receptor status. NSAID use reduced invasive breast cancer risk by about 20 %. A similar effect was found for aspirin, acetaminophen, COX-2 inhibitors and, to a lesser extent, ibuprofen. The effect of aspirin was similar in preventing hormone-receptor-positive breast cancer. This meta-analysis suggests a slightly protective effect of NSAIDs-especially aspirin and COX-2 inhibitors- against breast cancer, which seems to be restricted to ER/PR+tumors.

Results of observational studies: analysis of findings from the Nurses' Health Study

Background

The role of observational studies in informing clinical practice is debated, and high profile examples of discrepancies between the results of observational studies and randomised controlled trials (RCTs) have intensified that debate. We systematically reviewed findings from the Nurses’ Health Study (NHS), one of the longest and largest observational studies, to assess the number and strength of the associations reported and to determine if they have been confirmed in RCTs.

Methods

We reviewed NHS publication abstracts from 1978–2012, extracted information on associations tested, and graded the strength of the reported effect sizes. We searched PubMed for RCTs or systematic reviews for 3 health outcomes commonly reported in NHS publications: breast cancer, ischaemic heart disease (IHD) and osteoporosis. NHS results were compared with RCT results and deemed concordant when the difference in effect sizes between studies was ≤0.15.

Findings

2007 associations between health outcomes and independent variables were reported in 1053 abstracts. 58.0% (1165/2007) were statistically significant, and 22.2% (445/2007) were neutral (no association). Among the statistically significant results that reported a numeric odds ratio (OR) or relative risk (RR), 70.5% (706/1002) reported a weak association (OR/RR 0.5–2.0), 24.5% (246/1002) a moderate association (OR/RR 0.25–0.5 or 2.0–4.0) and 5.0% (50/1002) a strong association (OR/RR ≤0.25 or ≥4.0). 19 associations reported in NHS publications for breast cancer, IHD and osteoporosis have been tested in RCTs, and the concordance between NHS and RCT results was low (≤25%).

Conclusions

NHS publications contain a large number of analyses, the majority of which reported statistically significant but weak associations. Few of these associations have been tested in RCTs, and where they have, the agreement between NHS results and RCTs is poor.

Cyclooxygenase-2 and the inflammogenesis of breast cancer

Cohesive scientific evidence from molecular, animal, and human investigations supports the hypothesis that constitutive overexpression of cyclooxygenase-2 (COX-2) is a ubiquitous driver of mammary carcinogenesis, and reciprocally, that COX-2 blockade has strong potential for breast cancer prevention and therapy. Key findings include the following: (1) COX-2 is constitutively expressed throughout breast cancer development and expression intensifies with stage at detection, cancer progression and metastasis; (2) essential features of mammary carcinogenesis (mutagenesis, mitogenesis, angiogenesis, reduced apoptosis, metastasis and immunosuppression) are linked to COX-2-driven prostaglandin E2 (PGE-2) biosynthesis; (3) upregulation of COX-2 and PGE-2 expression induces transcription of CYP-19 and aromatase-catalyzed estrogen biosynthesis which stimulates unbridled mitogenesis; (4) extrahepatic CYP-1B1 in mammary adipose tissue converts paracrine estrogen to carcinogenic quinones with mutagenic impact; and (5) agents that inhibit COX-2 reduce the risk of breast cancer in women without disease and reduce recurrence risk and mortality in women with breast cancer. Recent sharp increases in global breast cancer incidence and mortality are likely driven by chronic inflammation of mammary adipose and upregulation of COX-2 associated with the obesity pandemic. The totality of evidence clearly supports the supposition that mammary carcinogenesis often evolves as a progressive series of highly specific cellular and molecular changes in response to induction of constitutive over-expression of COX-2 and the prostaglandin cascade in the “inflammogenesis of breast cancer”.

Cancer/stroma interplay via cyclooxygenase-2 and indoleamine 2,3-dioxygenase promotes breast cancer progression

INTRODUCTION

Expression of indoleamine 2,3-dioxygenase (IDO) in primary breast cancer increases tumor growth and metastasis. However, the clinical significance of stromal IDO and the regulation of stromal IDO are unclear.

METHODS

Metabolomics and enzyme-linked immunosorbent assay (ELISA) were used to study the effect of cyclooxygenase-2 (COX-2)-overexpressing breast cancer cells on IDO expression in co-cultured human breast fibroblasts. Biochemical inhibitors and short-hairpin RNA (shRNA) were used to clarify how prostaglandin E2 (PGE2) upregulates IDO expression. Associations of stromal IDO with clinicopathologic parameters were tested in tumor specimens. An orthotopic animal model was used to examine the effect of COX-2 and IDO inhibitors on tumor growth.

RESULTS

Kynurenine, the metabolite generated by IDO, increases in the supernatant of fibroblasts co-cultured with COX-2-overexpressing breast cancer cells. PGE2 released by cancer cells upregulates IDO expression in fibroblasts through an EP4/signal transducer and activator of transcription 3 (STAT3)-dependent pathway. Conversely, fibroblast-secreted kynurenine promotes the formation of the E-cadherin/Aryl hydrocarbon receptor (AhR)/S-phase kinase-associated protein 2 (Skp2) complex, resulting in degradation of E-cadherin to increase breast cancer invasiveness. The enhancement of motility of breast cancer cells induced by co-culture with fibroblasts is suppressed by the IDO inhibitor 1-methyl-tryptophan. Pathological analysis demonstrates that upregulation of stromal IDO is a poor prognosis factor and is associated with of COX-2 overexpression. Co-expression of cancer COX-2 and stromal IDO predicts a worse disease-free and metastasis-free survival. Finally, COX-2 and IDO inhibitors inhibit tumor growth in vivo.

CONCLUSION

Integration of metabolomics and molecular and pathological approaches reveals the interplay between cancer and stroma via COX-2, and IDO promotes tumor progression and predicts poor patient survival.

Clinical evidence of the relationship between aspirin and breast cancer risk (review)

In the search for new therapeutic alternatives against cancer, either as a preventive treatment or for advanced stages, it is common to appeal to well-known drugs used for the treatment of other diseases that may interfere with the metabolic pathways involved in carcinogenesis. Non-steroidal anti-inflammatory drugs (NSAIDs) display anticancer activity through the inhibition of the COX-2 enzyme, triggering processes such as apoptosis, a reduction in proliferation and inhibition of carcinogenesis. Breast cancer is a neoplasm with the highest incidence and mortality rate among young women worldwide. Epidemiologic data have shown that drugs such as NSAIDs, particularly aspirin, reduce the relative risk of breast cancer. However, in the subgroup of responsive patients, dose, time and frequency of use have not yet been established. Here, we review the reports published during the last 10 years regarding the relationship between breast cancer and aspirin.

Breast cancer prevention by antihormones and other drugs: where do we stand?

Breast cancer is the most common cancer in women worldwide. The selective estrogen-receptor (ER) modulators tamoxifen and raloxifene are approved by the Food and Drug Administration for the preventive therapy of breast cancer. Other drugs have shown promise but need further assessment. In the present review, we present an update of the chemoprevention of ER-positive breast cancer and discuss the potential role of metformin and aspirin, 2 drugs other than the specific "antihormones."

Low-dose aspirin use and cancer characteristics: a population-based cohort study

Background:

Long-term daily use of aspirin has been associated with reduced cancer mortality. To explore this association, we compared tumour TNM characteristics among aspirin users with those among non-users.

Methods:

From the Swedish Cancer Register, we identified patients diagnosed with colorectal, lung, prostate and breast cancers between 2006 and 2009 and matched them to the Swedish Prescribed Drug Register to obtain information on low-dose aspirin use prior to diagnosis. Contingency table and logistic regression analyses were used to test for association and obtain odds ratios (ORs).

Results:

We identified 17 041 colorectal, 9766 lung, 29 770 prostate and 20 299 breast cancer patients. The proportion of low-dose aspirin users was ∼26% among colorectal, lung and prostate cancer patients and ∼14% among breast cancer patients. Adjusted for age, gender, education level and place of residence, low-dose aspirin use was associated with lower tumour extent (T) for colorectal and lung cancers (P<0.0001) but not for prostate and breast cancers. The adjusted OR of aspirin use for the T4 vs T1 categories was ∼0.7 (95% confidence interval (CI) 0.6–0.8). For all cancers, we found no evidence of association of aspirin use with nodal involvement (N). Except for a borderline result in prostate cancer (OR ∼0.9; 95% CI 0.8–1.0), aspirin use was associated with a lower rate of metastatic disease (ORs ∼0.6–0.8). Among the histological subgroups of lung cancer, significant differences in tumour extent were observed most clearly within the adenocarcinoma subgroup (OR ∼0.6, 95% CI 0.5–0.8), although numbers of other subtypes were more limited; and there was a significant reduction of ∼20–30% in the odds of metastasis among the aspirin users across the subgroups.

Conclusion:

Use of low-dose aspirin in the year prior to diagnosis was found to be associated with lower tumour extent and fewer metastatic disease for colorectal and lung cancers. For these cancers, the benefit of aspirin use appears to be during both early and late cancer progression.

COX-Independent Mechanisms of Cancer Chemoprevention by Anti-Inflammatory Drugs

Epidemiological and clinical studies suggest that non-steroidal anti-inflammatory drugs (NSAIDs), including cyclooxygenase (COX)-2 selective inhibitors, reduce the risk of developing cancer. Experimental studies in human cancer cell lines and rodent models of carcinogenesis support these observations by providing strong evidence for the antineoplastic properties of NSAIDs. The involvement of COX-2 in tumorigenesis and its overexpression in various cancer tissues suggest that inhibition of COX-2 is responsible for the chemopreventive efficacy of these agents. However, the precise mechanisms by which NSAIDs exert their antiproliferative effects are still a matter of debate. Numerous other studies have shown that NSAIDs can act through COX-independent mechanisms. This review provides a detailed description of the major COX-independent molecular targets of NSAIDs and discusses how these targets may be involved in their anticancer effects. Toxicities resulting from COX inhibition and the suppression of prostaglandin synthesis preclude the long-term use of NSAIDs for cancer chemoprevention. Furthermore, chemopreventive efficacy is incomplete and treatment often leads to the development of resistance. Identification of alternative NSAID targets and elucidation of the biochemical processes by which they inhibit tumor growth could lead to the development of safer and more efficacious drugs for cancer chemoprevention.

Developmental windows of breast cancer risk provide opportunities for targeted chemoprevention

The magnitude of the breast cancer problem implores researchers to aggressively investigate prevention strategies. However, several barriers currently reduce the feasibility of breast cancer prevention. These barriers include the inability to accurately predict future breast cancer diagnosis at the individual level, the need for improved understanding of when to implement interventions, uncertainty with respect to optimal duration of treatment, and negative side effects associated with currently approved chemoprevention therapies. None-the-less, the unique biology of the mammary gland, with its postnatal development and conditional terminal differentiation, may permit the resolution of many of these barriers. Specifically, lifecycle-specific windows of breast cancer risk have been identified that may be amenable to risk-reducing strategies. Here, we argue for prevention research focused on two of these lifecycle windows of risk: postpartum mammary gland involution and peri-menopause. We provide evidence that these windows are highly amenable to targeted, limited duration treatments. Such approaches could result in the prevention of postpartum and postmenopausal breast cancers, correspondingly.

Eicosanoids and adipokines in breast cancer: from molecular mechanisms to clinical considerations

Chronic inflammation is one of the foremost risk factors for different types of malignancies, including breast cancer. Additional risk factors of this pathology in postmenopausal women are weight gain, obesity, estrogen secretion, and an imbalance in the production of adipokines, such as leptin and adiponectin. Various signaling products of transcription factor, nuclear factor-kappaB, in particular inflammatory eicosanoids, reactive oxygen species (ROS), and cytokines, are thought to be involved in chronic inflammation-induced cancer. Together, these key components have an influence on inflammatory reactions in malignant tissue damage when their levels are deregulated endogenously. Prostaglandins (PGs) are well recognized in inflammation and cancer, and they are solely biosynthesized through cyclooxygenases (COXs) from arachidonic acid. Concurrently, ROS give rise to bioactive isoprostanes from arachidonic acid precursors that are also involved in acute and chronic inflammation, but their specific characteristics in breast cancer are less demonstrated. Higher aromatase activity, a cytochrome P-450 enzyme, is intimately connected to tumor growth in the breast through estrogen synthesis, and is interrelated to COXs that catalyze the formation of both inflammatory and anti-inflammatory PGs such as PGE(2), PGF(2α), PGD(2), and PGJ(2) synchronously under the influence of specific mediators and downstream enzymes. Some of the latter compounds upsurge the intracellular cyclic adenosine monophosphate concentration and appear to be associated with estrogen synthesis. This review discusses the role of COX- and ROS-catalyzed eicosanoids and adipokines in breast cancer, and therefore ranges from their molecular mechanisms to clinical aspects to understand the impact of inflammation.

Use of aspirin, other nonsteroidal anti-inflammatory drugs, and acetaminophen and postmenopausal breast cancer incidence

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.

Aspirin and cancer risk: a quantitative review to 2011

BACKGROUND

Aspirin has been associated to a reduced risk of colorectal and possibly of a few other common cancers.

METHODS

To provide an up-to-date quantification of this association, we conducted a meta-analysis of all observational studies on aspirin and 12 selected cancer sites published up to September 2011.

RESULTS

Regular aspirin is associated with a statistically significant reduced risk of colorectal cancer [summary relative risk (RR) from random effects models = 0.73, 95% confidence interval (CI) 0.67-0.79], and of other digestive tract cancers (RR = 0.61, 95% CI = 0.50-0.76, for squamous cell esophageal cancer; RR = 0.64, 95% CI = 0.52-0.78, for esophageal and gastric cardia adenocarcinoma; and RR = 0.67, 95% CI = 0.54-0.83, for gastric cancer), with somewhat stronger reductions in risk in case-control than in cohort studies. Modest inverse associations were also observed for breast (RR = 0.90, 95% CI = 0.85-0.95) and prostate cancer (RR = 0.90, 95% CI = 0.85-0.96), while lung cancer was significantly reduced in case-control studies (0.73, 95% CI = 0.55-0.98) but not in cohort ones (RR = 0.98, 95% CI = 0.92-1.05). No meaningful overall associations were observed for cancers of the pancreas, endometrium, ovary, bladder, and kidney.

CONCLUSIONS

Observational studies indicate a beneficial role of aspirin on colorectal and other digestive tract cancers; modest risk reductions were also observed for breast and prostate cancer. Results are, however, heterogeneous across studies and dose-risk and duration-risk relationships are still unclear.

COX-2 expression predicts worse breast cancer prognosis and does not modify the association with aspirin

Some previous studies have found worse prognosis among cyclooxygenase-2 (COX-2)-expressing breast cancers. Aspirin and NSAIDs inhibit COX-2. Three studies, including ours, have reported a survival advantage among women with breast cancer who take either aspirin or NSAIDs. Through this study we hypothesized that in the Nurses' Health Study (NHS), COX-2 expression would be associated with worse prognosis, and aspirin use would be associated with better survival particularly among women with COX-2 positive tumors. In this study we investigated 2,001 women presenting with invasive breast cancers stained for COX-2 by immunohistochemistry. Tumor prognostic factors were from medical records. Aspirin use was assessed at least 12 months after diagnosis and updated. Cause of death was identified from death certificates. Statistical analyses included logistic regression of prognostic factors with COX-2 status as the outcome, and proportional hazards regression with breast cancer death as the outcome. Tumor COX-2 expression was associated with higher diagnostic stage. Compared with stage I, the RR(95% CI) for stages II-IV were 1.16 (0.93-1.45), 1.68 (1.27-2.22), and 1.76 (0.93-3.32). COX-2 expression was associated with lobular compared with ductal histology (1.40 [1.02-1.92]), and estrogen receptor positive compared with negative (2.22 [1.66-2.95]). The RR(95% CI) of breast cancer death for current aspirin use was similar for women with COX-2-positive and COX-2-negative tumors; 0.64 (0.43-0.96) and 0.57 (0.44-0.74), respectively. In the NHS, COX-2 breast cancer expression was associated with higher stage at diagnosis. The survival benefit associated with aspirin use did not differ by COX-2 status. COX-2 breast cancer expression is associated with worse prognosis. If aspirin truly impacts breast cancer survival, then it is not solely via COX-2.

Aspirin use and breast cancer risk: a meta-analysis

Animal and in vitro studies suggest that the use of aspirin may be associated with reduced risk for breast cancer, but results from these studies of the association have been inconsistent. The objective of this meta-analysis was to quantitatively summarize the current evidence for such a relationship. We searched MEDLINE for studies of aspirin use and breast cancer risk that were published in any language, from January 1, 1966, to July 1, 2011. A total of 33 studies (19 cohort studies, 13 case-control studies, and 1 randomized controlled trial [RCT]) that included 1,916,448 subjects were identified. We pooled the relative risks from individual studies using a random-effects model, heterogeneity, and publication bias analyses. In a pooled analysis of all studies, aspirin use was associated with reduced risk for breast cancer (odds ratio [OR] = 0.86, 95% confidence interval [CI] = 0.81, 0.92). In the subgroup analysis by study design, results were similar except for RCT (OR = 0.98, 95% CI = 0.87, 1.09). In conclusion, this meta-analysis indicated that regular use of aspirin may be associated with reduced risk of breast cancer. More RCT were needed to confirm this association in the future.

Regular aspirin use and breast cancer risk in US Black women

BACKGROUND

Epidemiologic studies have yet to provide consistent evidence to support a protective effect of aspirin and other non-steroidal anti-inflammatory drugs (NSAID) on the incidence of breast cancer.

OBJECTIVE

We evaluated the relations of current use of aspirin, non-aspirin NSAIDs, and acetaminophen with breast cancer incidence in the Black Women's Health Study.

METHODS

Biennial follow-up of 59,000 study participants began in 1995. During 558,600 person-years of follow-up through 2007, 1,275 breast cancer cases were identified. Using Cox proportional hazards regression, we estimated incidence rate ratios (IRR) and 95% confidence intervals (CI) for associations of current and former use of aspirin, other NSAIDs, and acetaminophen with incident breast cancer.

RESULTS

After adjustment for age, education, body mass index at age 18, physical activity, female hormone use, current smoking, and other NSAID use, the IRRs were 0.79 (95% CI = 0.66, 0.95) for current aspirin use and 0.68 (95% CI = 0.50, 0.92) for ≥5 years of aspirin use. Similar associations were observed for acetaminophen use.

CONCLUSIONS

Both aspirin and acetaminophen use were inversely associated with breast cancer incidence in the present study. Reasons for the association with acetaminophen use are unclear, given that acetaminophen has very weak anti-inflammatory effects.

Effect of aspirin and other NSAIDs on postmenopausal breast cancer incidence by hormone receptor status: results from a prospective cohort study

Aspirin and other non-aspirin non-steroidal anti-inflammatory drugs (NSAIDs) can inhibit aromatase activity and thus could selectively lower incidence of hormone receptor positive tumors. We assessed whether the association of aspirin and other NSAIDs with postmenopausal breast cancer risk differs by estrogen and progesterone receptor (ER and PR) status of the tumor. A population-based cohort of 26,580 postmenopausal women was linked to a SEER Cancer Registry to identify incident breast cancers. Regular use of aspirin and other NSAIDs was reported on a self-administered questionnaire mailed in 1992. Cox proportional hazards models were used to estimate multivariate relative risks (RRs) and 95% confidence intervals (CIs) of breast cancer incidence overall and by ER and PR status, adjusting for multiple breast cancer risk factors. Through 2005, 1,581 incident breast cancer cases were observed. Compared to aspirin never users, women who regularly consumed aspirin had a lower risk of breast cancer (RR = 0.80; 95% CI: 0.71-0.90), and there was evidence for lower risk with increasing frequency of use (RR = 0.71 for aspirin use 6 or more times/week vs. never use; P trend = 0.00001). Inverse associations for regular aspirin use were observed for ER+ (RR = 0.77; 95% CI 0.67-0.89), ER- (RR = 0.78; 95% CI 0.56-1.08), PR+ (RR = 0.79; 95% CI 0.68-0.92), and PR- (RR = 0.73; 95% CI 0.56-0.95) breast cancers. In contrast, use of other NSAIDs was not associated with breast cancer incidence overall (RR = 0.95, 95% CI: 0.85-1.07), or by ER or PR status. Aspirin, but not other NSAID use, was associated with about 20% lower risk of postmenopausal breast cancer and did not vary by ER or PR status of the tumor, suggesting that the hypothesized protective effects of aspirin may either be through cellular pathways independent of estrogen or progesterone signaling, or on tumor microenvironment.

Pre-surgical study of the biological effects of the selective cyclo-oxygenase-2 inhibitor celecoxib in patients with primary breast cancer

Cyclo-oxygenase 2 (COX-2) is implicated in the regulation of aromatase transcription in malignant breast tissue and has been considered as a potential target for tissue specific aromatase suppression. We initiated a randomised controlled pre-surgical study of celecoxib versus no treatment in women with primary breast cancer to determine the effects of COX-2 inhibition on markers of biological response. Postmenopausal women (50-80 years of age) with stage I or II, primary breast cancer, were randomised 2:1 to receive 400 mg/day celecoxib or no treatment for 14 days prior to surgery. A core biopsy was obtained pre- and post-treatment. Paired baseline and endpoint biopsies were analysed for Ki67, apoptosis, COX-2, CD31, estrogen receptor (ER) and progesterone receptor (PgR). Comparisons between the treatment groups were conducted using the Mann-Whitney test with a two-sided 5% significance. Of the 25 patients treated, 23 had evaluable data and 19 (83%) were ER positive. Overall the geometric mean change in Ki67, the primary end point, relative to baseline in the celecoxib arm was -16.6% (P = 0.056). The change in the no-treatment group was -8.1% (P = 0.24). There was no statistically significant difference in the change between the two groups. Celecoxib did not significantly affect apoptosis, COX-2, ER or PgR expression. There is only modest evidence for a biological effect of celecoxib in primary breast cancer. However, the trend towards a reduction in Ki67 in ER-positive breast cancer warrants further investigations in a larger cohort of patients.

Non-steroidal anti-inflammatory drug (NSAID) use and breast cancer risk in the Western New York Exposures and Breast Cancer (WEB) Study

OBJECTIVE

Chronic inflammation is suspected to have a role in breast carcinogenesis. Results of studies of non-steroidal anti-inflammatory drugs (NSAIDs) and breast cancer have been inconsistent. Timing of exposure and analysis of individual NSAIDs should be considered.

METHODS

We conducted a population-based case-control study in western New York State between 1996 and 2001. Cases, 35-79 years, had incident, primary, histologically confirmed breast cancer (n = 1,170). Controls (n = 2,115) were randomly selected from NY Department of Motor Vehicles records (<65 years) or Medicare rolls (>or=65 years). Participants were queried on use of aspirin, ibuprofen, and acetaminophen in the year prior and on aspirin during adulthood. Unconditional logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

Recent aspirin use was inversely associated with breast cancer risk (adjusted OR 0.80, 95% CI: 0.68-0.94); the strongest reduction in risk was observed among those who took >or=2 pills/day on days that aspirin was taken (OR 0.74, 95% CI: 0.61-0. 90). Adult lifetime use was also associated with breast cancer risk (>10 days/month, adjusted OR 0.68, 95% CI: 0.46-1.00). Use of ibuprofen or acetaminophen was not associated with breast cancer.

CONCLUSIONS

This is the first study to investigate the association of adult lifetime aspirin intake with breast cancer risk. Our findings provide evidence that aspirin use throughout a woman's life may confer some benefit.

Critical Overview on the Benefits and Harms of Aspirin

Aspirin is widely used internationally for a variety of indications, with the most prominent one being that of cardiovascular disease. However, aspirin has also been proposed as a treatment option in a diverse range of conditions such as diabetes mellitus, cancer prevention, and obstetrics. In our overview, we critically appraise the current evidence from recent systematic reviews and meta-analyses covering the benefits of aspirin across these conditions. We also look at evidence that some patients may not derive benefit due to the concept of aspirin resistance. Aspirin is also associated with the potential for significant harm, principally from haemorrhagic adverse events. We critically appraise the threat of haemorrhagic complications, and weigh up these risks against that of any potential benefit.

Prescriptions for selective cyclooxygenase-2 inhibitors, non-selective non-steroidal anti-inflammatory drugs, and risk of breast cancer in a population-based case-control study

INTRODUCTION

Non-steroidal anti-inflammatory drugs (NSAIDs) prevent the growth of mammary tumours in animal models. Two population-based case-control studies suggest a reduced risk of breast cancer associated with selective cyclooxygenase-2 (sCox-2) inhibitor use, but data regarding the association between breast cancer occurrence and use of non-selective NSAIDs are conflicting.

METHODS

We conducted a population-based case-control study using Danish healthcare databases to examine if use of NSAIDs, including sCox-2 inhibitors, was associated with a reduced risk of breast cancer. We included 8,195 incident breast cancer cases diagnosed in 1991 through 2006 and 81,950 population controls.

RESULTS

Overall, we found no reduced breast cancer risk in ever users (>2 prescriptions) of sCox-2 inhibitors (odds ratio (OR) = 1.08, 95% confidence interval (95% CI) = 0.99, 1.18), aspirin (OR = 0.98, 95% CI = 0.90-1.07), or non-selective NSAIDs OR = 1.04, (95% CI = 0.98, 1.10)). Recent use (>2 prescriptions within two years of index date) of sCox-2 inhibitors, aspirin, or non-selective NSAIDs was likewise not associated with breast cancer risk (Ors = 1.06 (95% CI = 0.96, 1.18), 0.96 (95% CI = 0.87, 1.06) and 0.99 (95% CI = 0.85, 1.16), respectively). Risk estimates by duration (<10, 10 to 15, 15+ years) or intensity (low/medium/high) of NSAID use were also close to unity. Regardless of intensity, shorter or long-term NSAID use was not significantly associated with breast cancer risk.

CONCLUSIONS

Overall, we found no compelling evidence of a reduced risk of breast cancer associated with use of sCox-2 inhibitors, aspirin, or non-selective NSAIDs.

Aspirin intake and survival after breast cancer

PURPOSE

Animal and in vitro studies suggest that aspirin may inhibit breast cancer metastasis. We studied whether aspirin use among women with breast cancer decreased their risk of death from breast cancer.

METHODS

This was a prospective observational study based on responses from 4,164 female registered nurses in the Nurses' Health Study who were diagnosed with stages I, II, or III breast cancer between 1976 and 2002 and were observed until death or June 2006, whichever came first. The main outcome was breast cancer mortality risk according to number of days per week of aspirin use (0, 1, 2 to 5, or 6 to 7 days) first assessed at least 12 months after diagnosis and updated.

RESULTS

There were 341 breast cancer deaths. Aspirin use was associated with a decreased risk of breast cancer death. The adjusted relative risks (RRs) for 1, 2 to 5, and 6 to 7 days of aspirin use per week compared with no use were 1.07 (95% CI, 0.70 to 1.63), 0.29 (95% CI, 0.16 to 0.52), and 0.36 (95% CI, 0.24 to 0.54), respectively (test for linear trend, P < .001). This association did not differ appreciably by stage, menopausal status, body mass index, or estrogen receptor status. Results were similar for distant recurrence. The adjusted RRs were 0.91 (95% CI, 0.62 to 1.33), 0.40 (95% CI, 0.24 to 0.65), and 0.57 (95% CI, 0.39 to 0.82; test for trend, P = .03) for 1, 2 to 5, and 6 to 7 days of aspirin use, respectively.

CONCLUSION

Among women living at least 1 year after a breast cancer diagnosis, aspirin use was associated with a decreased risk of distant recurrence and breast cancer death.

Convergence of hormones, inflammation, and energy-related factors: a novel pathway of cancer etiology

Colorectal cancer (CRC) is a multifactorial disease with several hypothesized etiologic factors including inflammatory processes; hormones such as estrogen, androgen, and insulin; and energy-related factors. We present evidence that integrates these elements in a pathway we call the convergence of hormones, inflammation, and energy-related factors (CHIEF). First, given the physiology of the gut, substantial epidemiologic and molecular data support the hypothesis that activation of innate immunity in the normal gut mucosa by various environmental agents (commensal bacteria, dietary antigens, mucosal irritants, pathogens) and endogenous factors such as estrogen, androgens, and insulin levels provokes basal inflammation as an underlying factor of the association of insulin, estrogen, and energy-related factors with CRC. Second, critical genes involved in this pathway, e.g., phosphatase tensin homologue on chromosome 10 (PTEN) and serine threonine kinase 11 (STK11)/LKB1, are tumor suppressor genes often mutated in intestinal cancer or CRC. Third, laboratory experiments show that cellular PTEN and STK11/LKB1 tumor suppressor enzymes are vulnerable to inactivation by redox-active species, especially chemically reactive lipid mediators of inflammation and redox stress. Epidemiologic data further support the underlying proposal that CHIEF comprises important elements of CRC risk. Although this discussion of the CHIEF pathway focuses on CRC, we believe that this pathway may play an important role in the etiology of other cancers as well.

Use of aspirin, other nonsteroidal anti-inflammatory drugs, and acetaminophen and risk of breast cancer among premenopausal women in the Nurses' Health Study II

BACKGROUND

The use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) is widespread for treatment of common symptoms such as headaches, muscular pain, and inflammation. In addition, the chemopreventive use of NSAIDs is increasingly common for heart disease and colon cancer. Evidence of a protective association with breast cancer risk has been inconsistent, and few data exist for premenopausal women.

METHODS

We assessed the associations for use of aspirin, other NSAIDs, and acetaminophen with breast cancer risk among premenopausal women in the prospective Nurses' Health Study II. In total, 112,292 women, aged 25 to 42 years and free of cancer in 1989, were followed up until June 2003. Multivariate relative risks and 95% confidence intervals were calculated by Cox proportional hazards models, adjusting for age and other important breast cancer risk factors.

RESULTS

Overall, 1345 cases of invasive premenopausal breast cancer were documented. Regular use of aspirin (> or = 2 times per week) was not significantly associated with breast cancer risk (relative risk, 1.07; 95% confidence interval, 0.89-1.29). Regular use of either nonaspirin NSAIDs or acetaminophen also was not consistently associated with breast cancer risk. Results did not vary by frequency (days per week), dose (tablets per week), or duration of use. Furthermore, associations with each drug category did not vary substantially by estrogen and progesterone receptor status of the tumor.

CONCLUSION

These data suggest that the use of aspirin, other NSAIDs, and acetaminophen is not associated with a reduced risk of breast cancer among premenopausal women.

Aspirin and cancer risk: a summary review to 2007

Aspirin has been associated with a reduced risk of colorectal cancer and--based on limited evidence--to cancers of the oesophagus, stomach, breast, ovary and lung. The role of aspirin on other cancers, such as pancreatic, prostate and bladder cancer and non-Hodgkin's lymphomas and myeloma is less clear, and an increase of risk has been suggested for kidney cancer. For most cancer sites, however, significant heterogeneity between studies, and particularly between study design, was found, with a reduction in risk generally stronger in case-control studies than in cohort ones.

Use of common medications and breast cancer risk

Prescription and over-the-counter medications are widely used in the United States and many western countries. More than two-thirds of women ages >45 years, who are at greatest risk for breast cancer, take prescription medication. In light of the ubiquitous nature of medication use and the fact that breast cancer remains the most common cancer in women, research on the role of medication use in breast cancer etiology is warranted. We summarize the epidemiologic evidence on the association between breast cancer risk and use of common medications, including antibiotics, antidepressants, statins, antihypertensives, and nonsteroidal anti-inflammatory drugs. Overall, there is little evidence that would implicate the use of antibiotics, antidepressants, statins, and antihypertensives in the etiology of breast cancer. Although several prospective studies and a randomized low-dose aspirin chemoprevention trial have not shown lower risk of breast cancer among aspirin users, most studies that have examined the potential chemoprotective effect of nonsteroidal anti-inflammatory drugs have shown significant risk reductions for regular and prolonged use of these drugs. The existing literature on the role of medication use in breast carcinogenesis is complicated. Interpretation of the evidence is hampered due to major methodologic differences across studies, including exposure assessment, exposure classification, and adjustment for potential confounding variables. These differences largely stem from the fact that the majority of articles on this topic represent secondary data analyses from studies with inadequate information on exposure or confounders. Thus, future epidemiologic studies specifically designed to study these ubiquitous and biologically plausible exposures are warranted.

Association between NSAIDs use and breast cancer risk: a systematic review and meta-analysis

The association between non-steroidal anti-inflammatory drugs (NSAIDs) use and breast cancer has remained controversial. Therefore, an overall quantitative estimate of the association needs to be studied. A systematic review and meta-analysis was executed to explore the pooled estimate for relative risk (RR) and 95% confidence interval (CI) using random or fixed effects models based on heterogeneity analysis. Overall 26 studies with 528,705 participants were included. The RR of NSAIDs use and the incidence of breast cancer was 0.94 (95% CI: 0.88-1.00) with random effects model. A slight reduction of breast cancer by taking aspirin and ibuprofen was both observed with pooled RR of 0.91 (95% CI: 0.83-0.98) and 0.81 (95% CI: 0.67-0.97), respectively. Our results indicate that NSAIDs use is associated with a slight decrease for the development of breast cancer with a marginally statistical significant difference. The associations are slightly more obvious in aspirin and ibuprofen use.

Migraine in postmenopausal women and the risk of invasive breast cancer

BACKGROUND

The frequency of migraine headache changes at various times of a woman's reproductive cycle. Menarche, menses, pregnancy, and perimenopause may carry a different migraine risk conceivably because of fluctuating estrogen levels, and in general, migraine frequency is associated with falling estrogen levels. Given the strong relationship between endogenous estrogen levels and breast cancer risk, migraine sufferers may experience a reduced risk of breast cancer.

METHODS

We combined data from two population-based case-control studies to examine the relationship between migraine and risk of postmenopausal invasive breast cancer among 1,199 ductal carcinoma cases, 739 lobular carcinoma cases, and 1,474 controls 55 to 79 years of age. Polytomous logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

Women who reported a clinical diagnosis of migraine had reduced risks of ductal carcinoma (OR, 0.67; 95% CI, 0.54-0.82) and lobular carcinoma (OR, 0.68; 95% CI, 0.52-0.90). These associations were primarily limited to hormone receptor-positive tumors as migraine was associated with a 0.65-fold (95% CI, 0.51-0.83) reduced risk of estrogen receptor-positive (ER+)/progesterone receptor-positive (PR+) ductal carcinoma. The reductions in risk observed were seen among migraine sufferers who did and did not use prescription medications for their migraines.

CONCLUSIONS

These data suggest that a history of migraine is associated with a decreased risk of breast cancer, particularly among ER+/PR+ ductal and lobular carcinomas. Because this is the first study to address an association between migraine history and breast cancer risk, additional studies are needed to confirm this finding.