Association of Diabetes and Other Clinical and Sociodemographic Factors With Guideline-concordant Breast Cancer Treatment for Breast Cancer.

BACKGROUND: Women with breast cancer have worse health outcomes with co-occurring type 2 diabetes, possibly due to suboptimal breast cancer treatment. METHODS: We created a cohort of women ages 66 to 85 y with stage I to III breast cancer from 1993 to 2012 from an integrated health care delivery system (n=1612) and fee-for-service Medicare beneficiaries (n=98,915), linked to Surveillance, Epidemiology, and End Results (SEER) data (total n=100,527). We evaluated associations between type 2 diabetes and other factors with undergoing guideline-concordant cancer treatment. We estimated χ tests for univariate analysis and relative risks (RRs) using multivariable log-binomial models for outcomes of (1) overall guideline-concordant treatment, (2) definitive surgical therapy (mastectomy or lumpectomy with radiation), (3) chemotherapy if indicated, and (4) endocrine therapy. RESULTS: Our cohort included 60% of subjects with stage 1 tumors, one quarter below 70 years old, 23% had diabetes, 35% underwent overall guideline-concordant treatment, 24% chemotherapy, and 83% endocrine therapy. Women with diabetes were less likely to undergo overall guideline-concordant treatment (RR: 0.96; 95% confidence interval: 0.94-0.98), and only slightly less likely to undergo guideline-concordant definitive surgical therapy (RR: 0.99; 95% confidence interval: 0.99-1.00). No differences were found for chemotherapy or endocrine therapy. Other factors significantly associated with a lower risk of guideline-concordant care were cancer stages II to III (vs. I; RR=0.47-0.69, P<0.0001), older age (vs. 66 to 69 y; RR=0.56-0.90, P<0.0001), higher comorbidity burden, and Medicaid dual-eligibility. CONCLUSIONS: Diabetes was associated with lower adherence to overall guideline-concordant breast cancer treatment. However, higher stage, older age, higher comorbidity burden, and Medicaid insurance were more strongly associated with lower use of guideline-concordant treatment. Given the heavy burden of breast cancer and diabetes, long-term outcomes analysis should consider guideline-concordant treatment. IMPACT: Other factors besides diabetes are more strongly associated with guideline-concordant breast cancer treatment.

Diabetes and differences in detection of incident invasive breast cancer.

Many women diagnosed with breast cancer have chronic conditions such as diabetes that may impact other health behaviors. Our purpose was to determine if breast cancer screening and detection differs among women with and without diabetes. We conducted a cross-sectional analysis of a retrospective cohort of women aged 52-74 years diagnosed with incident stages I-III breast cancer enrolled in an integrated health plan between 1999 and 2014 with linkage to the Surveillance, Epidemiology and End Results registry (n = 2040). Screening data were taken from electronic health records. We used multivariable modified Poisson regression models with robust standard errors to estimate relative risks (RR) and 95% confidence intervals (CI) for outcomes of (i) receipt of screening in the 2 years prior to diagnosis; (ii) symptom-detected breast cancer; and (iii) diagnosis of locally advanced stage III breast cancer. Compared to women without diabetes, women with diabetes were similar with respect to receipt of screening mammography (78% and 77%), symptom-detected breast cancer (46% and 49%), and stage III diagnosis (7% and 7%). In multivariable models adjusting for age and year of diagnosis, race, BMI, Charlson comorbidity score and depression diagnosis no differences were observed in the outcomes by presence of diabetes. Further investigation is warranted to determine how diabetes acts as a mediating factor in adverse breast cancer outcomes.

Use of antidepressants after colon cancer diagnosis and risk of recurrence.

OBJECTIVE: Prior research examining the association between use of antidepressants after colon cancer diagnosis and risk of recurrence is scant. We evaluated this association among colon cancer patients diagnosed at two integrated health care delivery systems in the United States. METHODS: We conducted a cohort study of stage I to IIIA colon cancer patients diagnosed at greater than or equal to 18 years of age at Kaiser Permanente Colorado and Kaiser Permanente Washington during 1995 to 2014. We used pharmacy records to identify dispensings for antidepressants and tumor registry records and patients' medical charts to identify cancer recurrences. Using Cox proportional hazards models, we estimated the adjusted hazard ratio (HR) of colon cancer recurrence comparing patients who used antidepressants after diagnosis to those who did not. We also evaluated the risk associated with use of selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs) separately. RESULTS: Among the 1923 eligible colon cancer patients, 807 (42%) used an antidepressant after diagnosis and 139 had a colon cancer recurrence during an average 5.6 years of follow-up. Use of antidepressants after colon cancer diagnosis was not associated with risk of recurrence (HR: 1.14; 95% confidence interval [CI], 0.69-1.87). The HR for use of SSRIs was 1.22 (95% CI, 0.64-2.30), and for TCAs, it was 1.18 (95% CI, 0.68-2.07). CONCLUSIONS: Our findings suggest that use of antidepressants after colon cancer diagnosis was common and not associated with risk of recurrence. Future larger studies with greater power to examine risk associated with individual antidepressants would be valuable additions to the evidence base.

Risk of colon cancer recurrence in relation to diabetes.

PURPOSE: To describe the association between diabetes and colon cancer recurrence. METHODS: We conducted a cohort study at two integrated health care delivery systems in the United States. Using tumor registry data, we identified patients aged ≥ 18 years when diagnosed with stage I-IIIA adenocarcinomas of the colon during 1995-2014. Pre-existing diabetes was ascertained via diagnosis codes. Medical records were reviewed for eligibility and to abstract recurrence and covariate information. Recurrence was ascertained beginning 90 days after the end of colon cancer treatment (i.e., cohort entry). Recurrence of any cancer or a new primary cancer at any site was a secondary outcome. We used multivariable Cox proportional hazards models to estimate hazard ratios (HR) and 95% confidence intervals (CIs) for the associations between diabetes at cohort entry and study outcomes. RESULTS: Among the 1,923 eligible patients, 393 (16.7%) had diabetes at cohort entry. Diabetes was not associated with recurrence (HR 0.87; 95% CI 0.56-1.33) or with any subsequent cancer (HR 1.09; 95% CI 0.85-1.40). When the definition of recurrence included second primary colorectal cancer, risk was non-significantly higher in patients with diabetes than without diabetes. CONCLUSIONS: The risk of colon cancer recurrence appears to be similar in patients with and without diabetes at diagnosis. IMPACT: Future studies should evaluate the association between diabetes and colorectal cancer outcomes, especially second primary colon cancers, in larger populations.

Proton Pump Inhibitor Use and Dementia Risk: Prospective Population-Based Study.

OBJECTIVES: To determine whether higher cumulative proton pump inhibitor (PPI) exposure is associated with greater dementia risk. DESIGN: Prospective population-based cohort study. SETTING: Kaiser Permanente Washington, an integrated healthcare delivery system in Seattle, Washington. PARTICIPANTS: Individuals aged 65 and older without dementia at study entry (N = 3,484). MEASUREMENTS: Participants were screened for dementia every 2 years, and those who screened positive underwent extensive evaluation. Dementia outcomes were determined using standard diagnostic criteria. Time-varying PPI exposure was determined from computerized pharmacy data and consisted of total standardized daily doses (TSDDs) dispensed to an individual in the prior 10 years. We also assessed duration of use. Multivariable Cox regression was used to estimate the association between PPI exposure and time to dementia or Alzheimer's disease (AD). RESULTS: Over a mean follow-up of 7.5 years, 827 participants (23.7%) developed dementia (670 with possible or probable AD). PPI exposure was not associated with risk of dementia (P = .66) or AD (P = .77). For dementia, the risk for specific levels of cumulative exposure compared to no use was: 365 TSDDs (HR 0.87, 95% CI 0.65-1.18), 1,095 TSDDs (HR 0.99, CI 0.75-1.30) and 1,825 TSDDs (HR 1.13, CI 0.82-1.56). These TSDD levels represent approximately 1, 3 and 5 years of daily use respectively. Duration of PPI use was not associated with dementia outcomes either. CONCLUSION: Proton pump inhibitor use was not associated with dementia risk, even for people with high cumulative exposure. Although there are other safety concerns with long-term PPI use, results from our study do not support that these medications should be avoided out of concern about dementia risk.

Anesthesia Exposure and Risk of Dementia and Alzheimer's Disease: A Prospective Study.

OBJECTIVES: To evaluate the associations between anesthesia and dementia or Alzheimer's disease (AD) risk using prospectively collected data. DESIGN: Cohort study. PARTICIPANTS: Community-dwelling members of the Adult Changes in Thought cohort aged 65 and older and free of dementia at baseline (N = 3,988). MEASUREMENTS: Participants self-reported all prior surgical procedures with general or neuraxial (spinal or epidural) anesthesia at baseline and reported new procedures every 2 years. People undergoing high-risk surgery with general anesthesia, other surgery with general anesthesia, and other surgery with neuraxial anesthesia exposures were compared with those with no surgery and no anesthesia. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for dementia and AD associated with time-varying lifetime and recent (past 5 years) anesthesia exposures. RESULTS: At baseline, 254 (6%) people reported never having anesthesia; 248 (6%) had had one or more high-risk surgeries with general anesthesia, 3,363 (84%) had had one or more other surgeries with general anesthesia, and 123 (3%) had had one or more surgeries with neuraxial anesthesia. High-risk surgery with general anesthesia was not associated with greater risk of dementia (HR = 0.86, 95% CI = 0.58-1.28) or AD (HR = 0.95, 95% CI = 0.61-1.49) than no history of anesthesia. People with any history of other surgery with general anesthesia had a lower risk of dementia (HR = 0.63, 95% CI = 0.46-0.85) and AD (HR = 0.65, 95% CI = 0.46-0.93) than people with no history of anesthesia. There was no association between recent anesthesia exposure and dementia or AD. CONCLUSION: Anesthesia exposure was not associated with of dementia or AD in older adults.

Benzodiazepine use and risk of incident dementia or cognitive decline: prospective population based study.

OBJECTIVE: To determine whether higher cumulative use of benzodiazepines is associated with a higher risk of dementia or more rapid cognitive decline. DESIGN: Prospective population based cohort. SETTING: Integrated healthcare delivery system, Seattle, Washington. PARTICIPANTS: 3434 participants aged ≥ 65 without dementia at study entry. There were two rounds of recruitment (1994-96 and 2000-03) followed by continuous enrollment beginning in 2004. MAIN OUTCOMES MEASURES: The cognitive abilities screening instrument (CASI) was administered every two years to screen for dementia and was used to examine cognitive trajectory. Incident dementia and Alzheimer's disease were determined with standard diagnostic criteria. Benzodiazepine exposure was defined from computerized pharmacy data and consisted of the total standardized daily doses (TSDDs) dispensed over a 10 year period (a rolling window that moved forward in time during follow-up). The most recent year was excluded because of possible use for prodromal symptoms. Multivariable Cox proportional hazard models were used to examine time varying use of benzodiazepine and dementia risk. Analyses of cognitive trajectory used linear regression models with generalized estimating equations. RESULTS: Over a mean follow-up of 7.3 years, 797 participants (23.2%) developed dementia, of whom 637 developed Alzheimer's disease. For dementia, the adjusted hazard ratios associated with cumulative benzodiazepine use compared with non-use were 1.25 (95% confidence interval 1.03 to 1.51) for 1-30 TSDDs; 1.31 (1.00 to 1.71) for 31-120 TSDDs; and 1.07 (0.82 to 1.39) for ≥ 121 TSDDs. Results were similar for Alzheimer's disease. Higher benzodiazepine use was not associated with more rapid cognitive decline. CONCLUSION: The risk of dementia is slightly higher in people with minimal exposure to benzodiazepines but not with the highest level of exposure. These results do not support a causal association between benzodiazepine use and dementia.

Prescription Opioids and Risk of Dementia or Cognitive Decline: A Prospective Cohort Study.

OBJECTIVES: To determine whether prescription opioid use is associated with higher dementia risk or greater cognitive decline. DESIGN: Prospective cohort study. SETTING: Group Health, an integrated healthcare delivery system. PARTICIPANTS: Community-dwelling individuals aged 65 and older without dementia with at least 10 years of Group Health enrollment at baseline (N = 3,434; median age 74). MEASUREMENTS: The Cognitive Abilities Screening Instrument (CASI) was administered every 2 years. Low scores triggered detailed evaluation, and a multidisciplinary committee assigned dementia diagnoses. From computerized pharmacy data, cumulative opioid exposure was defined as total standardized doses (TSDs) dispensed over 10 years (excluding the most recent year because of possible prodromal symptoms). For comparison, use of nonsteroidal anti-inflammatory drugs (NSAIDs), characterized similarly, was examined. Dementia risk was analyzed using Cox proportional hazards models and CASI trajectory using linear regression models and generalized estimating equations. RESULTS: Seven hundred ninety-seven participants (23%) developed dementia over a mean follow-up of 7.3 years; 637 (19%) had possible or probable Alzheimer's disease. For cumulative opioid use, the hazard ratios (HRs) for dementia were 1.06 (95% confidence interval (CI) = 0.88-1.26) for 11 to 30 TSDs, 0.88 (95% CI = 0.70-1.09) for 31 to 90 TSDs, and 1.29 (95% CI = 1.02-1.62) for 91 or more TSDs, versus 0 to 10 TSDs. A similar pattern was seen for NSAID use. Heavier opioid use was not associated with more-rapid cognitive decline. CONCLUSION: People with the heaviest opioid or NSAID use had slightly higher dementia risk than people with little or no use. These results may reflect an effect of chronic pain on cognition or residual confounding. Although opioids have other risks, little evidence of long-term cognitive harm specific to opioids was found.

Associations between diabetes medication use and risk of second breast cancer events and mortality.

PURPOSE: Diabetes and certain diabetes medications have been shown to influence breast cancer (BC) risk. Less is known about their relation to BC outcomes. Our objective was to evaluate the effects of diabetes and diabetes medications on risk of second breast cancer events (SBCE) and mortality. METHODS: This population-based cohort study was conducted among women diagnosed with early-stage (I-II) BC and enrolled in an integrated health plan. Exposures of interest were diabetes and medication classes including insulin, metformin, and sulfonylureas. Outcomes of interest were SBCE defined as recurrence or second primary BC, BC-specific mortality, and all-cause mortality. We used multivariable Cox proportional hazards models to estimate hazard ratios (HR) and 95 % confidence intervals (CI) for diabetes and medication use while accounting for potential confounders and competing risks. RESULTS: Among 4,216 women, 13 % developed SBCE during a median follow-up of 6.3 years. 610 women had diabetes of which 76 % used oral diabetes medication and/or insulin. Findings suggested that diabetes increased the risk of recurrence (HR = 1.57; 95 % CI 1.09-2.25) but not overall SBCE (HR = 1.29; 95 % CI 0.94-1.76) or second primary BC (HR = 0.74; 95 % CI 0.39-1.41). Among women with diabetes, insulin use was associated with increased risks of recurrence (HR = 1.94; 95 % CI 1.08-3.48) and all-cause mortality (HR = 2.33; 95 % CI 1.70-3.20). Metformin use was associated with lower all-cause mortality (HR = 0.55; 95 % CI 0.38-0.79). CONCLUSIONS: Our findings show an association between diabetes and increased recurrence risk, and risk may be greater among insulin users. Metformin may reduce all-cause mortality among BC survivors. Given the growing breast cancer survivor population, further research in larger, more diverse populations is warranted.

Cumulative use of strong anticholinergics and incident dementia: a prospective cohort study.

IMPORTANCE: Many medications have anticholinergic effects. In general, anticholinergic-induced cognitive impairment is considered reversible on discontinuation of anticholinergic therapy. However, a few studies suggest that anticholinergics may be associated with an increased risk for dementia. OBJECTIVE: To examine whether cumulative anticholinergic use is associated with a higher risk for incident dementia. DESIGN, SETTING, AND PARTICIPANTS: Prospective population-based cohort study using data from the Adult Changes in Thought study in Group Health, an integrated health care delivery system in Seattle, Washington. We included 3434 participants 65 years or older with no dementia at study entry. Initial recruitment occurred from 1994 through 1996 and from 2000 through 2003. Beginning in 2004, continuous replacement for deaths occurred. All participants were followed up every 2 years. Data through September 30, 2012, were included in these analyses. EXPOSURES: Computerized pharmacy dispensing data were used to ascertain cumulative anticholinergic exposure, which was defined as the total standardized daily doses (TSDDs) dispensed in the past 10 years. The most recent 12 months of use was excluded to avoid use related to prodromal symptoms. Cumulative exposure was updated as participants were followed up over time. MAIN OUTCOMES AND MEASURES: Incident dementia and Alzheimer disease using standard diagnostic criteria. Statistical analysis used Cox proportional hazards regression models adjusted for demographic characteristics, health behaviors, and health status, including comorbidities. RESULTS: The most common anticholinergic classes used were tricyclic antidepressants, first-generation antihistamines, and bladder antimuscarinics. During a mean follow-up of 7.3 years, 797 participants (23.2%) developed dementia (637 of these [79.9%] developed Alzheimer disease). A 10-year cumulative dose-response relationship was observed for dementia and Alzheimer disease (test for trend, P < .001). For dementia, adjusted hazard ratios for cumulative anticholinergic use compared with nonuse were 0.92 (95% CI, 0.74-1.16) for TSDDs of 1 to 90; 1.19 (95% CI, 0.94-1.51) for TSDDs of 91 to 365; 1.23 (95% CI, 0.94-1.62) for TSDDs of 366 to 1095; and 1.54 (95% CI, 1.21-1.96) for TSDDs greater than 1095. A similar pattern of results was noted for Alzheimer disease. Results were robust in secondary, sensitivity, and post hoc analyses. CONCLUSIONS AND RELEVANCE: Higher cumulative anticholinergic use is associated with an increased risk for dementia. Efforts to increase awareness among health care professionals and older adults about this potential medication-related risk are important to minimize anticholinergic use over time.

Comparative safety of cardiovascular medication use and breast cancer outcomes among women with early stage breast cancer.

Breast cancer tends to occur in an older age group of women also burdened with comorbidities such as cardiovascular disease (CVD). Numerous medications used to manage CVD (e.g., statins and antihypertensives) are hypothesized to alter breast cancer risk, but there are few studies on breast cancer outcomes. The COmmonly used Medications and Breast Cancer Outcomes (COMBO) cohort was developed to study how medications and co-morbidities influence breast cancer prognosis. Cohort study among adult women, diagnosed with incident early stage breast cancer, and enrolled in an integrated health plan. Data sources included health plan administrative databases, Surveillance, Epidemiology, and End Results tumor registry, and medical records. Statins, angiotensin-converting enzyme inhibitors (ACEI), beta blockers (BB), calcium blockers, and diuretics were the exposures of interest. The outcome was second breast cancer events (SBCE) defined as recurrence or second primary breast cancer. We used multivariable Cox proportional hazards models to estimate hazard ratios (HR) and 95 % confidence intervals (CI) for SBCE, and components of SBCE. 4,216 women were followed for a median of 6.3 years, and 13.2 % experienced a SBCE (first of: n = 415 recurrences and n = 143 s primary breast cancers). Compared to non-users, we observed an increased risk of second primary breast cancer with ACEI use (HR = 1.66; 95 % CI, 1.06-2.58) and an increased risk of recurrence with BB use (HR = 1.29; 95 % CI, 1.01-1.64). There was suggestion of a reduced risk of SBCE with statin use (HR = 0.82; 95 % CI, 0.62-1.08) and second primary breast cancer with BB use (HR = 0.77; 95 % CI, 0.50-1.19). No differences in outcomes were observed by duration of medication use. A majority of CVD medications evaluated in this study appear safe with respect to SBCE, but ACEI and BB use warrant further evaluation. The study presented is one example of the questions that can be addressed using the COMBO cohort.

Administrative data algorithms to identify second breast cancer events following early-stage invasive breast cancer.

BACKGROUND: Studies of breast cancer outcomes rely on the identification of second breast cancer events (recurrences and second breast primary tumors). Cancer registries often do not capture recurrences, and chart abstraction can be infeasible or expensive. An alternative is using administrative health-care data to identify second breast cancer events; however, these algorithms must be validated against a gold standard. METHODS: We developed algorithms using data from 3152 women in an integrated health-care system who were diagnosed with stage I or II breast cancer in 1993-2006. Medical record review served as the gold standard for second breast cancer events. Administrative data used in algorithm development included procedures, diagnoses, prescription fills, and cancer registry records. We randomly divided the cohort into training and testing samples and used a classification and regression tree analysis to build algorithms for classifying women as having or not having a second breast cancer event. We created several algorithms for researchers to use based on the relative importance of sensitivity, specificity, and positive predictive value (PPV) in future studies. RESULTS: The algorithm with high specificity and PPV had 89% sensitivity (95% confidence interval [CI] = 84% to 92%), 99% specificity (95% CI = 98% to 99%), and 90% PPV (95% CI = 86% to 94%); the high-sensitivity algorithm had 96% sensitivity (95% CI = 93% to 98%), 95% specificity (95% CI = 94% to 96%), and 74% PPV (95% CI = 68% to 78%). CONCLUSIONS: Algorithms based on administrative data can identify second breast cancer events with high sensitivity, specificity, and PPV. The algorithms presented here promote efficient outcomes research, allowing researchers to prioritize sensitivity, specificity, or PPV in identifying second breast cancer events.

Statin use and female reproductive organ cancer risk in a large population-based setting.

OBJECTIVE: Statins are an effective and commonly used cholesterol-lowering medication class, but their hypothesized effects on cancer risk remain uncertain. We evaluated the association between statin use and endometrial as well as ovarian cancer risks. METHODS: We conducted a retrospective study with two cohorts of women aged 45-89 years during 1990-2004 within an integrated healthcare delivery system. Information on statin use and covariates were obtained from automated databases. We identified cancer cases through the Surveillance, Epidemiology, and End Results registry. Multivariable Cox proportional hazards models were used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) for incident invasive endometrial and ovarian cancers among statin users compared to nonusers. RESULTS: Women were followed for a median of about six years. Among 73,336 women studied, 568 endometrial cancer cases were identified. During the study period, 6% of women used statins for at least one year and the median duration of use was 3.1 years. Although not statistically significant, we found a reduction in endometrial cancer risk among statin users (HR = 0.67; 95% CI: 0.39-1.17) compared to nonusers. We identified 326 ovarian cancer cases in a cohort of 93,619 women. There was also a nonsignificant decrease in ovarian cancer risk among statin users (HR = 0.69; 95% CI: 0.32-1.49). CONCLUSION: Our study does not support an association between statin use and endometrial as well as ovarian cancers, but a reduced risk cannot be ruled out.

Statin use and prostate cancer risk in a large population-based setting.

BACKGROUND: Statins are a commonly used cholesterol-lowering drug, which also have the potential to affect cancer risk and progression. Results from previous studies offer mixed conclusions. METHODS: To evaluate the relation between statin use and prostate cancer risk, we conducted a retrospective cohort study during 1 January 1990 to 31 August 2005 among men 45-79 years receiving care within Group Health, an integrated healthcare delivery system. Information on statin use and covariates were obtained from health plan databases. We identified incident prostate cancer cases through the Surveillance, Epidemiology, and End Results cancer registry. We used Cox proportional hazards models to estimate the hazard ratios (HR) and 95% confidence intervals (CI) for prostate cancer among statin users compared to non-users. RESULTS: Among 83,372 men studied, median follow-up time was 5.7 years and 2,532 prostate cancer cases were identified. About 14.4% used statins over the study period and median duration of use was 3.3 years. Compared to non-users, hydrophobic statin users had a reduced risk of prostate cancer (HR = 0.79; 95% CI, 0.66-0.94), and results are suggestive of a reduced risk among ever users of statins (HR = 0.88; 95% CI, 0.76-1.02) and hydrophilic statin users (HR = 0.67; 95% CI, 0.33-1.34). There was no trend in risk by duration of statin use, and no association between statin use and cancer aggressiveness, stage, or grade. CONCLUSION: Overall, this study does not support an associated between statin use and prostate cancer but a reduced risk cannot be ruled out.

Statin use and breast cancer risk in a large population-based setting.

BACKGROUND: Mechanistic studies suggest that 3-hydroxy-3-methylglutaryl CoA inhibitors (statins) reduce the risk of breast cancer. Observational studies offer mixed results. METHODS: To evaluate the relation between statin use and breast cancer risk, we conducted a cohort study among women ages 45 to 89 years within an integrated health care delivery system. Information on statin use and covariates were obtained from automated databases. We identified breast cancer cases through the Surveillance, Epidemiology, and End Results registry. We used Cox proportional hazards models to estimate the hazard ratios (HR) and 95% confidence intervals (95% CI) for invasive breast cancer among statin users compared with nonusers. RESULTS: Among 92,788 women studied from 1990 to 2004, median follow-up time was 6.4 years, and 2,707 breast cancer cases were identified. During the study period, 7.4% of women used statins for at least 1 year, and the median duration of use was 3.1 years. We found no difference in breast cancer risk among statin users (HR, 1.07; 95% CI, 0.88-1.29) compared with nonusers. Risk of breast cancer did not differ by duration of use (1-2.9, 3-4.9, or >or=5 years) or hydrophobic statin use. We found a suggestive increased risk of breast cancer among statin users of >or=5 years (HR, 1.27; 95% CI, 0.89-1.81 for any statins and HR, 1.47; 95% CI, 0.89-2.44 for hydrophobic statins) and of estrogen receptor-negative tumors with increasing duration of statin use (1-2.9 years: HR, 1.33; 95% CI, 0.64-2.77; 3-4.9 years: HR, 1.68; 95% CI, 0.72-3.92; >or=5 years: HR, 1.81; 95% CI, 0.75-4.36). CONCLUSION: This study does not support an association between statin use and breast cancer risk.