Table 5.

Epidemiologic studies of the role of NSAID use in breast cancer development

Study and countryYearsDesignCases/controlsExposure measurementMajor findingsConfoundersComments
Schreinemachers and Everson (110) USA1971-1975Cohort1,257 cases identified via the National Health and Examination Survey IIn-person and telephone interviews, hospital and nursing home recordsIncident risk ratio for all sites combined for aspirin users vs nonaspirin users (30 d before interview)Gender, ageAdjustment for following variables did not appreciably effect incident risk ratio: race, education, smoking, alcohol
11,411 cancer-free cohort membersAll sites combined: 0.83 (0.74-0.93), lung cancer: 0.68 (0.49-0.94), breast cancer in women: 0.70 (0.50-0.96), and colorectal cancer in younger men: 0.35 (0.17-0.73)
Harris et al. (95) USA1988-1992Hospital-based case-control studyCases: 744 patients with newly diagnosed breast cancer identified by collaborating hospitals in northeastern United StatesIn-person interview1-4 y NSAID use vs none: 1.09 (0.8-1.5), ≥5 y NSAID use vs none: 0.63 (0.5-0.9)Age, menopausal status, parity, family history of breast cancer, BMI
Controls: 767 patients without cancer diagnoses frequency matched to cases
Egan et al. (117) USA1980-1992Cohort2,414 cases of invasive breast cancer (2,303 confirmed with medical records and 111 cases identified by questionnaire response)Self-administered questionnaire, medical record reviewRegular aspirin use from 1980 to 1988 vs no regular use: 1.01 (0.80-1.27)Age at menarche, age at menopause, BMI, alcohol, family history of breast cancer, history of benign breast disease, multivitamin useAuthors concluded that regular aspirin use does not reduce breast cancer risk
Heavy use from 1980 to 1988 vs no regular use: 1.09 (0.75-1.60)
≥20 y regular use vs no regular use: 1.00 (0.71-1.41)
Harris et al. (99) USANot notedPopulation-based case-control studyCases: 511 newly diagnosed breast cancer confirmed by pathology reportIn-person interviewRegular NSAID use vs no regular use: 0.66 (0.52-0.83)Age, parity, menopausal status, family history
Controls: 1,534 cancer-free women from central OH frequency matched by race and ageRegular aspirin use vs no regular use: 0.69 (0.46-0.99)
Regular ibuprofen use vs no regular use: 0.57 (0.36-0.91)
≥7 per week, ≥5 y NSAID use vs no regular use: 0.60 (0.40-0.91)
Harris et al. (113) USA1991-1993Cohort393 breast cancers have been detectedSelf-administered questionnaire1-3 NSAID pills per week vs <1: 0.64 (0.50-0.82), ≥4 vs <1: 0.57 (0.44-0.74)NoneAdjustment for the following variables did not appreciably effect risk estimates: age, education, parity, menopausal status, and family history of breast cancer
32,505 women enrolled in the mammography screening program of The Ohio State University Comprehensive Cancer Center (4.7 y average follow-up)
Coogan et al. (65) USA1976-1996Hospital-based case-control studyCases: 6,558 women with a first occurrence of primary breast cancer diagnosed within the previous year, confirmed by path report, and no concurrent or previous cancerIn-person interviewFor cancer controls: regular use within 1 y of admission only vs never use: 0.6 (0.4-1.0); regular use begun ≥1 y before admission vs never use: 0.8 (0.7-1.0)Age, study center, interview year, years of education, history of benign breast disease, number of doctor visits 2 y before admission, duration of oral contraceptive use, duration of use of female hormone supplementsAdjustment for the following variables did not appreciably effect risk estimates: age at menarche, age at menopause, age at first birth, parity, race, alcohol consumption, religion, breast cancer in mother or sister, practice of breast self-examination, BMI
Controls: 3,296 patients with other cancers not associated with NSAID use, 2,925 noncancer patientsFor noncancer controls: regular use within 1 y of admission only vs never use: 0.5 (0.3-0.8), regular use begun ≥1 y before admission vs never use: 0.7 (0.6-0.9)
Sharpe et al. (93) Canada1981-1995Registry-based studyCases: 5,882 women diagnosed with histologically proven invasive breast cancerSaskatchewan Prescription Drug Plan databaseNSAID exposure 2-5 y before diagnosis: average daily dose >0.3 vs ADD = 0: 0.76 (0.63-0.92)Sampling fractions, age, exposure during other periods, total duration of lactation, BMI after menopauseFor periods <2 and >5 y, there was no significant reduction in risk
Controls: 23,517 controls frequency matched on age and sampling timeJust cases, exposure 2-5 y before diagnosis: 0 < ADD ≤ 0.1 vs ADD = 0: 0.52 (0.37-0.73), 0.1 < ADD ≤ 0.3 vs ADD = 0: 0.53 (0.30-0.92), and ADD > 0.3 vs ADD = 0: 0.49 (0.24-0.99)
Khuder and Mutgi (120) N/AN/AMeta-analysisN/ALiterature database search through 2000NSAID use vs noneN/AThe numbers given in Table 3 are different than the numbers presented in the body of the article
14 articles were analyzed0.82 (0.75-0.89) in all studies, 0.78 (0.62-0.99) in 6 cohort studies, and 0.87 (0.84-0.91) in 8 case-control studies
Cotterchio et al. (98) Canada1996-1998Population-based case-control studyCases: 3,133 random women diagnosed with a first primary cancer of the breast, 25-74 y identified via Ontario Cancer RegistrySelf-report questionnaireAny regular NSAID use vs never: 0.76 (0.66-0.88)Age, history of arthritis, benign breast diseaseConfounders evaluated include HRT, oral contraceptive use, alcohol, smoking, weight, BMI, physical activity, history of arthritis, reproductive history, education, marital status, previous breast cysts, family history of breast cancer, other medication use, dietary fat intake
Controls: 3,062 age-matched random sample of the female population of Ontario≥9 y NSAID use vs never: 0.68 (0.54-0.86)
≤1 y since last NSAID use vs never: 0.64 (0.54-0.77)
Age at first use ≥50 vs never: 0.76 (0.61-0.93)
Meier et al. (128) UKRegistry-based studyCases: 3,706 women with incident breast cancerMedical history computer record20-29 acetaminophen prescriptions vs none: 0.7 (0.6-0.9)Smoking status, BMIAdjustment for following variables did not appreciably effect risk estimates: prior hysterectomy, prior oophorectomy, prior history of benign breast lumps, longer-term exposure to postmenopausal estrogens
Controls: 14,155 age, years of medical history in the computer record, general practice attended, and calendar time matched controls≥30 acetaminophen prescriptions vs none: 0.8 (0.7-1.0)Study contains no information about over-the-counter NSAID
No statistically significant difference found between number of NSAID prescriptions
Johnson et al. (111) USA1986-1997Cohort938 cases identified from the Iowa Women's Health StudySelf-administered questionnaireAspirin or NSAID use vs none: 0.80 (0.67-0.95)Age, BMI, estrogen use, family history of breast cancer, benign breast disease, multivitamin use, category of NSAID use, mammography, waist-to-hip ratio
27,616 total cohort membersAspirin use vs none: 0.82 (0.71-0.95)
NSAID use vs none: 0.98 (0.85-1.14)
≥6 aspirin use per week vs none: 0.71 (0.58-0.87)
In situ disease: ≥6 aspirin use vs none: 0.52 (0.30, 0.90)
Regional or distant disease: ≥6 aspirin use vs none: 0.50 (0.29-0.88)
Harris et al. (105) USANot notedCohort study1,392 self-reported incident cases confirmed by medical record reviewSelf-administered questionnaireAny NSAID use for ≥10 vs <1 y use: 0.72 (0.56-0.91)Age, ethnicity, education, BMI, HRT use, family history of breast cancer, parity at age <30 y, and episodes of weekly exerciseAdditional analyses stratified by BMI, HRT use, family history of breast cancer, parous at age <30 y, and episodes per week of moderate/strenuous exercise did not vary appreciably from full sample
80,741 women in total cohort (43-mo average follow-up)Aspirin use for ≥10 vs <1 y use: 0.79 (0.60-1.03)
Ibuprofen use for ≥10 vs <1 y use: 0.51 (0.28-0.96)
Moorman et al. (100) USA1996-2000Population-based case-control studyCases: 930 cases of invasive breast cancer identified via North Carolina Central Cancer RegistryIn-person interviewAny NSAID use vs none: 0.4 (0.3-0.6)Age, race, age at menarche, age at first full-term pregnancy, breastfeeding history, menopausal status, family history, oral contraceptive use, HRT use, education, BMI, waist-to-hip ratio, smoking status, and offset term
Controls: 754 controls selected from DMV and Health Care Financing Administration, frequency matched to cases on age and ethnicityOccasional NSAID use vs none: 0.5 (0.3-0.7)
Regular NSAID use ≥3 y vs none: 0.3 (0.2-0.5)
Gonzalez-Perez et al. (122) N/AN/AMeta-analysisN/ALiterature database search from 1966 to 2002 for cohort or case-control studiesNSAID use vs none: 0.77 (0.66-0.88)N/A
15 of 47 studies reporting outcomes for breast cancer were analyzedAspirin use vs none: 0.77 (0.69-0.86)
Garcia Rodriguez and Gonzalez-Perez (104) UK1995-2001Registry-based studyCases: 3,708 cases of invasive breast cancer identified from General Practice ResearchGeneral practice database/electronic medical recordAspirin use ≥4 y vs none: 0.86 (0.61-1.19)Age, calendar year, BMI, alcohol intake, smoking status, HRT use, prior benign breast disease, and remaining NSAID
DatabaseNonaspirin NSAID (ibuprofen) use ≥4 y vs none: 0.94 (0.74-1.21)
Controls: 20,000 cancer-free controls from cohort matched to cases on age and calendar year (study cohort = 734,899 women)Acetaminophen use ≥4 y vs none: 0.77 (0.64-0.94)
Terry et al. (102) USA1996-1997Population-based case-control studyCases: 1,508 invasive or in situ breast cancer cases confirmed by medical record reviewIn-person interviews, medical recordsAspirin use ≥7 times/wk for ≥5 y vs none: 0.77 (0.57-1.04)Age at diagnosis, migraine headache, BMI
Controls: 1,556 controls selected though random-digit dialing methods and Health Care Financing Administration lists, frequency matched to cases in 5-y age intervalsIbuprofen use ≥3 times/wk for ≥5 y vs none: 1.09 (0.70-1.70)
Ever used aspirin and hormone receptor positive vs none: 0.74 (0.60-0.93)
Ever used aspirin and hormone receptor negative vs none: 0.97 (0.67-1.40)
Harris et al. (160) N/AN/AMeta-analysisN/ALiterature database search through 1970-2003All studies NSAID vs no use: RR, 0.61 (0.50-0.75)N/A
17 studies
Jacobs et al. (115) USA1992-2001Cohort study3008 incident cases identified via self-report and confirmed via medical record or state cancer registriesSelf-administered questionnaire≥60 tablets of any NSAID per month vs none: 1.07 (0.96-1.21)Age, race, education, family history of breast cancer, personal history of breast cysts, history of mammography, age at menarche, duration of oral contraceptive use, parity, age at menopause, HRT use, weight change, BMI, alcohol consumption
97,786 women in total cohort≥60 aspiring tablets per month vs none: 1.01 (0.84-1.20)
≥60 ibuprofen tablets per month vs none: 1.06 (0.89-1.26)
≥5 y current regular NSAID use vs none: 1.05 ((0.88-1.26)
≥5 y current regular aspirin use vs none: 0.88 (0.69-1.12)
≥5 y current regular ibuprofen use vs none: 1.29 (0.92-1.82)
Zhang et al. (97) USA1976-2002Hospital-based case-control studyCases: 7,006 primary breast cancer cases confirmed from discharge summaries and pathology reportsIn-person interview≥20 y regular aspirin use vs none: 0.59 (0.25-1.36)Age, year of interview, study center, race, year of education, benign breast disease, number of physician visits 2 y before hospitalization, duration of HRT use, duration of oral contraceptive use, age at menarche, age at menopause, age at first birth, parity, alcohol consumption, family history of breast cancer, practice of breast self-exam, and BMI
Controls: 3,622 controls admitted for nonmalignant conditions≥5 y regular ibuprofen use v none: 0.78 (0.29-2.08)
Regular use of aspirin and hormone receptor positive vs none: 0.74 (0.44-1.26)
Regular use of aspirin and hormone receptor negative vs none: 0.94 (0.45-1.96)
Regular use any NSAID and premenopausal vs none: 0.62 (0.41-0.94)
Regular use any NSAID and postmenopausal vs none: 0.90 (0.69-1.16)
Swede et al. (96) USA1982-1998Hospital-based case-control studyCases: 1,478 primary, incident cases confirmed via pathology reportSelf-administered questionnaireRegular aspirin use vs none: 0.85 (0.74-0.97)Age at menarche, age at first birth, BMI, history of first-degree relative with breast cancer, and history of benign breast disease
Controls: 3,383 cancer-free controls frequency matched to cases on 5-y age intervals≥7 aspirin tablets/week vs none: 0.74 (0.59-0.92)
≥10 y aspirin use vs none: 0.91 (0.78-1.06)
Daily regular use of aspirin for ≥10 y vs none: 0.72 (0.53-0.97)
Marshall et al. (116) USA1995-2001CohortCases: 2,391 primary incident cases confirmed by tumor registrySelf-administered questionnaire, cancer registry dataDaily use aspirin vs none: 0.98 (0.86-1.13); ≥5 y regular use vs none: 1.07 (0.96-1.20)Race, BMI, first-degree family history, menopausal and hormone therapy use status, smoking, alcohol intake, physical activity, mammography history, breast biopsy history, parity before age 30, neighborhood SES
114,640 disease-free cohort womenDaily use ibuprofen vs none: 1.24 (1.07-1.44); ≥5 y use vs none: 1.17 (1.00-1.36)
Daily use any NSAID vs none: 1.09 (0.97-1.21); ≥5 y regular use vs none: 1.11 (1.01-1.23)
Daily use acetaminophen vs none: 0.99 (0.74-1.31); ≥5 y vs none: 1.10 (0.95-1.27)
ER/PgR negative and aspirin use ≥ 5 y daily vs none: 1.81 (1.12-2.92); ER/PgR positive and ibuprofen use ≥5 y daily vs none: 1.50 (1.11-2.03)
Rahme et al. (129) Canada1998-2002Registry-based studyCases: 1,090 incident cases identified from mammography screening groupPopulation prescription/medical record databaseCOX-2 inhibitors ≥90 d vs none: 0.81 (0.68-0.97)Age, mammography in year 2 or 3 before index date, breast procedure in the prior 3 y, benign neoplasm of the breast in prior 3 y, other breast disease in the prior 3 y, HRT in prior year, visit to gynecologist in prior year
Controls: 44,990 disease-free women from mammography screening group (418,458 women in total cohort)NSAID ≥90 d vs none: 0.65 (0.43-0.99)
Aspirin > 100 mg/d for ≥90 d vs none: 0.75 (0.64-0.89)
Acetaminophen ≥90 d vs none: 0.91 (0.71-1.16)
Moorman et al. (108) USA1993-2001Population-based case-control studyCases: 763 cases of invasive or in situ breast cancer among African American womenIn-person interviews, genotyping by Taqman assayCOX-2 gene wild-type homozygous or heterozygous and regular NSAID use vs none: 0.3 (0.1-0.9)Age, offset term for oversampling younger and African American women
Controls: 678 disease-free African American population controls matched by ageCOX-2 gene variant homozygous and regular NSAID use vs none: 0.3 (0.2-0.6)
Cook et al. (118) USA1992-2004Randomized controlled trial39,876 women randomized into low-dose aspirin (19,934) and placebo (19,942) arms followed for self-reported cancer endpoints verified by medical record reviewSelf-administered questionnaireAspirin use vs placebo: 0.98 (0.87-1.09)None
Marginal interaction between aspirin use and smoking status, P < 0.09
Never smokers: 1.11 (0.94-1.30), former smokers: 0.84 (0.70-1.01), and current smokers: 0.93 (0.69-1.25)
Harris et al. (94) USA2003-2004Hospital-based case-control studyCases: 323 cases of histologically confirmed invasive breast cancerIn-person interviewDaily COX-2 inhibitor use ≥2 y vs none/infrequent use: 0.29 (0.14-0.59)Age, BMI, parity, menopausal status, family history, smoking and alcohol intakeNone/infrequent use defined as use of no more than one pill per week for <1 y
Controls: 649 age, race, and residence matched controls from hospital mammography serviceAspirin use 2 times per week for ≥2 y vs none/infrequent use: 0.49 (0.26-0.94)
Ibuprofen/naproxen use 2 times per week for ≥2 y vs none/infrequent use: 0.37 (0.18-0.72)
Gallicchio et al. (106) USA1989-2003CohortCases: 91 cases of invasive or in situ breast cancer identified via county and state cancer registriesSelf-report questionnaire, medical record data, and biological sample for COX genotyping via Taqman assayAspirin use in 1989 vs none: 0.46 (0.22-0.98)Age, type of NSAIDAdjustment for following variables did not appreciably effect risk estimates: education, age at menarche, menopausal status in 1989, alcohol consumption in 1989, family history of breast cancer, BMI in 1989, and parity
1,467 women with benign breast disease identified from larger CLUE II cohort of 14,625 womenAspirin use in 1996 vs none: 0.47 (0.18-1.21)
Any NSAID use in 1989 vs none: 0.60 (0.35-1.03)
Any NSAID use in 1996 vs none: 0.64 (0.32-1.27)
No association between COX genotype and breast cancer risk
Suggestion of significantly increased risk among those with COX-2 rs2143416 variant CC genotype and nonuse of NSAIDs
Shen et al. (109) USA1996-1997Population-based case-control studyCases: 1,067 in situ or invasive breast cancer cases included in the Long Island Breast Cancer Study ProjectIn-person interviewNo major effects of the three COX-2 variant alleles on breast cancer risk were foundAge at reference (defined as age at diagnosis for cases and age at identification for controls)Variables found not to confound associations of interest: age at menarche, parity, lactation, months of lactation, age at first birth, number of miscarriages, history of fertility problems, alcohol, race, education, religion, marital status
Controls: 1,110 frequency matched on age identified through random-digit dialingAmong women with hormone receptor-positive breast cancer, reduced risk for any NSAID use was only evident among those who had at least one variant C allele of COX-2 0.8473
NSAID use vs none: 0.7 (0.5-1.0)
P for the interaction = 0.02
Gill et al. (153) USA1993-2002Cohort1,830 breast cancer cases in the Multiethnic cohortSelf-administered questionnaireNo association between breast cancer risk and duration of aspirin use for current or past users vs nonusers was foundAge, ethnicity, BMI, family history of breast cancer, education, mammography screening, alcohol intake, age at menarche, age at fist live birth, number of children, menopausal status, and HRT
98,920 women in cohortDuration of current other NSAID use protective vs nonusers (≥6 y): 0.70 (0.51-0.95)
When stratified by ethnicity and hormone receptor status, the protective effect limited to Caucasians or African Americans or to women with at least one positive hormone receptor
Jacobs et al. (119) USA1992-2003Cohort571 breast cancer cases in Cancer Prevention Study II Nutrition cohortSelf-administered questionnaireLess than daily, low-dose, or past use vs no reported use: 1.10 (1.00-1.21)Age, race, education, smoking, BMI, physical activity level, use of HRT, history of mammography, history of colorectal endoscopy, use of use of nonaspirin NSAIDs, history of heart attack, diabetes, hypertensionAdjustment for following variables did not appreciably effect risk estimates: nutritional factors
76,303 total women in cohortNot statistically significant lower risk for current daily use (≥325 mg) ≥5 y: 0.83 (0.63-1.10)
Ready et al. (114) USA2000-2002Cohort482 breast cancer cases in VITAL cohort studySelf-administered questionnaireLow-dose aspirin overall use vs none: 0.99 (0.80-1.23)Age, race, BMI, family history of breast cancer, history of biopsy, mammogram in 2 y before baseline, age at menarche, age at first birth, age at menopause, history of surgical menopause, years of combined estrogen and progesterone hormone therapy, multivitamin use and alcohol use, adjustment for use of other categories of NSAIDs
35,323 total postmenopausal women in cohortLow-dose aspirin at ≥4 d/wk over 10 y vs none: 0.65 (0.43-0.91)
All NSAIDs (except for low-dose aspirin) overall use vs none: 0.98 (0.67-1.44)
All NSAIDs (except for low-dose aspirin) ≤1-3 d/wk over 10 y vs none: 0.78 (0.61-0.98)
All NSAIDs (except for low-dose aspirin) ≥4 d/wk over 10 y vs none: 1.26 (0.96-1.65)
Regular/extra-strength aspirin at ≥4 d/wk over 10 y vs none: 1.43 (1.02-2.00)
Gallicchio et al. (107) USA1989-2006Cohort430 cases of primary invasive breast cancer identified from cancer registriesIn-person interviewNonaspirin NSAID use in 1996 vs nonusers: 0.53 (0.31-0.93)Age at baselineAdjustment for following variables did not appreciably affect risk estimates: education, history of fibrocystic disease, family history of breast cancer, age at first menarche, hormone use, oral contraceptive use, menopausal status, parity, BMI
18,723 total women in cohortNSAID use at baseline and in 1996 vs no NSAID use at baseline and in 1996: 0.50 (0.28-0.91)
Bardia et al. (112) USA1992-2003Cohort3,487 incident cancer cases and 3,581 deaths were observed in the cohort of 22,507 postmenopausal womenSelf-administered questionnaireAspirin use vs nonuse was inversely associates with total cancer incidence: 0.84 (0.77-0.90) or cancer mortality: 0.87 (0.76-0.99)Age, education status, physical activity, use of HRT, marital status, BMI, diabetes status, fruit and vegetable intake, waist-to-hip ratio, history of hypertension, alcohol use, vitamin supplement use, total caloric intake, red meat consumption, whole-wheat consumption, vitamin E intake, cholesterol intake, history of osteoarthritis, and history of rheumatoid arthritisNo information according to sites
The inverse relationship was stronger among former and never smokers vs current smokers
Nonaspirin NSAID use was not associated with cancer incidence or mortality
Davis and Mirick (103) USA1992-1995Population-based case-control studyCases: 600 newly diagnosed breast cancerTelephone interviewNo association between risk of breast cancer and any measure of NSAID useParity, age at first pregnancy, mother/sister breast cancer, early double oophorectomy, oral contraceptive use, ever upper gastrointestinal series, and ever smoker (all subjects); mother/sister breast cancer ages <45 y and alcohol intake (if premenopausal) or HRT (if postmenopausal)
Controls: 647 from the Seattle metropolitan area, identified by random-digit dialing and frequency matched by 5-y age groupsEver regular NSAID use vs never: 1.1 (0.8-1.4)
<5 y vs never: 1.1 (0.7-1.8)
5-10 y vs never: 1.0 (0.7-1.5)
≥2 y before diagnosis vs never: 2.0 (0.9-4.3)
<2 y diagnosis vs never: 1.0 (0.7-1.3)
Among cases with localized disease, ≥2 y before diagnosis vs never: 2.2 (1.0-4.9)
Slattery et al. (101)1999-2004Population-based case-control studyCases: 798 Hispanic/Native American and 1,527 non-Hispanic White women diagnosed with first primary breast cancerIn-person interviewAspirin use vs nonuse among postmenopausal women with no recent hormone exposure: 0.56 (0.33-0.96)Age, study center, referent year BMI, lifetime physical activity score, parity, and percentage Native American ancestry
Controls: 935 Hispanic/Native American and 1,671 non-Hispanic White women from the target populations matched on ethnicity and 5-year age distribution of casesAspirin use among postmenopausal women with recent hormone exposure or premenopausal/perimenopausal women was not associated with breast cancer risk
Interleukin-6 genotype modified the association between aspirin and breast cancer among postmenopausal women with no recent hormone exposure (P for interaction = 0.04 for Hispanic/Native American and 0.06 for non-Hispanic White)
Friis et al. (82) Denmark1993-2003Cohort847 cases identified via the Danish Cancer RegistrySelf-administered questionnaire at baseline (1993-1997) and data updated using a nationwide prescription database through 2-3Any NSAID use at baseline vs nonuse: 1.27 (1.10-1.45)Age, school education, parity number of births, use of HRT, and history of benign breast tumor surgery
29,875 total cohort memberSimilar results were observed in a combined analysis of baseline and prescription data
Aspirin only use vs nonuse: 1.31 (1.12-1.53)
No differences in risk estimates with frequency, recency, or duration of NSAID use or by hormone receptor status of breast tumors
Mangiapane et al. (121) N/AN/AMeta-analysisN/ALiterature database search from 2001 to 2005 for cohort or case-control studiesAspirin use vs none: 0.74 (0.69-0.79) in all studies, 0.82 (0.73-0.92) in 4 cohort studies, and 0.70 (0.56-0.87) in 6 case-control studiesN/A
10 studies were analyzed
Zhang et al. (83) USA1992-2004Randomized controlled trial39,876 women randomized into low-dose aspirin (19,934) and placebo (19,942) arms followed for self-reported cancer endpoints verified by medical record reviewSelf-administered questionnaireLow-dose aspirin has no preventive effect of breast cancer in the subgroup analysis by tumor characteristics at diagnosisNone