The Ambulatory Diabetes Outreach Program (ADOP): Rigorous Evaluation of a Pharmacist and Nurse-Led Care Model.

BACKGROUND: Although several systematic reviews found that ambulatory diabetes mellitus (DM) interventions involving pharmacists generally yielded better outcomes than the ones that did not, existing studies have limitations in rigor and study design. OBJECTIVE: To examine the intention-to-treat effects of the Ambulatory Diabetes Outreach Program (ADOP) on participants' A1c values and healthcare utilization over a 52-month follow-up period. DESIGN: Difference-in-differences with staggered adoption. Specifically, we employed the Callaway and Sant'Anna's "group-time average treatment effect" estimator using not-yet treated as controls adjusting for patient's age, BMI, sex, race, comorbidity, payor, and socio-economic status. PARTICIPANTS: All patients with at least one ADOP treatment encounter from July 2017 to October 2021, regardless of program completion or length of exposure to the program. INTERVENTION: ADOP, a collaborative population health program led by pharmacists and nurse specialists to provide individualized type 2 DM management and education within a large and diverse health system. MAIN MEASURES: Patients' A1c values and healthcare utilization, including inpatient admission, inpatient days, and numbers of visits to the emergency department, urgent care, and primary care in recent 6 months. KEY RESULTS: ADOP participation was associated with an overall average reduction of 1.04 percentage points (95%CI - 1.12, - 0.95) in A1c level. Similar A1c reductions were also observed in the subgroups by sex and race/ethnicity. An average of 2 months were required to reach the overall average effect, which persisted over 4 years. Compared to the respective utilization levels pre-intervention, participants also had average reductions in inpatient admissions by 32.4%, inpatient days by 81.6%, visits to the emergency department by 21.6%, and primary care by 17.9%. CONCLUSIONS: The results suggest that a collaborative model of pharmacist and nurse-led type 2 DM intervention was effective in improving A1c outcomes and reducing healthcare utilization in the long term.

Breast Cancer Screening and Prevention.

Breast cancer is the most common cancer among U.S. women and its incidence increases with age. Endogenous estrogen exposure, proliferative benign breast disease, breast density, and family history may also indicate increased risk for breast cancer. Early detection with screening mammography reduces breast cancer mortality, but the net benefits vary by age. Assessing a patient's individual breast cancer risk can guide decisions regarding breast cancer screening. All women benefit from healthy behaviors which may reduce breast cancer risk. Some women at increased risk for breast cancer may benefit from risk-reducing medications. Use of screening measures remains suboptimal, especially for uninsured women.

Can Regionalization of Care Reduce Socioeconomic Disparities in Breast Cancer Survival?

BACKGROUND: Breast cancer patients of low socioeconomic status (SES) have worse survival than more affluent women and are also more likely to undergo surgery in low-volume facilities. Since breast cancer patients treated in high-volume facilities have better survival, regionalizing the care of low SES patients toward high-volume facilities might reduce SES disparities in survival. OBJECTIVE: We leverage a natural experiment in New York state to examine whether a policy precluding payment for breast cancer surgery for New York Medicaid beneficiaries undergoing surgery in low-volume facilities led to reduced SES disparities in mortality. RESEARCH DESIGN: A multivariable difference-in-differences regression analysis compared mortality of low SES (dual enrollees, Medicare-Medicaid) breast cancer patients to that of wealthier patients exempt from the policy (Medicare only) for time periods before and after the policy implementation. SUBJECTS: A total of 14,183 Medicare beneficiaries with breast cancer in 2006-2008 or 2014-2015. MEASURES: All-cause mortality at 3 years after diagnosis and Medicaid status, determined by Medicare administrative data. RESULTS: Both low SES and Medicare-only patients had better 3-year survival after the policy implementation. However, the decline in mortality was larger in magnitude among the low SES women than others, resulting in a 53% smaller SES survival disparity after the policy after adjustment for age, race, and comorbid illness. CONCLUSION: Regionalization of early breast cancer care away from low-volume centers may improve outcomes and reduce SES disparities in survival.

Prevalence and scope of advanced practice provider oncology care among Medicare beneficiaries with breast cancer.

PURPOSE: Advanced practice providers (APPs) have increasingly become members of the oncology care team. Little is known about the scope of care that APPs are performing nationally. We determined the prevalence and extent of APP practice and examined associations between APP care and scope of practice regulations, phase of cancer care, and patient characteristics. METHODS: We performed an observational study among women identified from Medicare claims as having had incident breast cancer in 2008 with claims through 2012. Outpatient APP care included at least one APP independently billing for cancer visits/services. APP scope of practice was classified as independent, reduced, or restricted. A logistic regression model with patient-level random effects was estimated to determine the probability of receiving APP care at any point during active treatment or surveillance. RESULTS: Among 42,550 women, 6583 (15%) received APP care, of whom 83% had APP care during the surveillance phase and 41% during the treatment phase. Among women who received APP care during a given year of surveillance, the overall proportion of APP-billed clinic visits increased with each additional year of surveillance (36% in Year 1 to 61% in Year 4). Logistic regression model results indicate that women were more likely to receive APP care if they were younger, black, healthier, had higher income status, or lived in a rural county or state with independent APP scope of practice. CONCLUSIONS: This study provides important clinical and policy-relevant findings regarding national practice patterns of APP oncology care. Among Medicare beneficiaries with incident breast cancer, 15% received outpatient oncology care that included APPs who were billing; most of this care was during the surveillance phase. Future studies are needed to define the degree of APP oncology practice and training that maximizes patient access and satisfaction while optimizing the efficiency and quality of cancer care.

Variation Among Primary Care Physicians in 30-Day Readmissions.

Background: Whether readmission rates vary by primary care physician (PCP) is unknown, although federal policy holds PCPs accountable for reducing readmissions. Objective: To determine whether 30-day readmission rates vary by PCP. Design: Retrospective cohort study using marginal models and multilevel logistic regression with 100% of data on Texas Medicare claims from 2008 to 2015. Setting: Texas. Participants: Patients discharged alive between 1 January 2008 and 30 November 2015 who had a PCP in the prior year and whose PCP had at least 50 admissions in the study period. Measurements: Readmission within 30 days of discharge. Follow-up visits with a PCP within 7 days of discharge were also measured. Results: Between 2012 and 2015, the mean risk-standardized rate of 30-day readmissions was 12.9%. Of 4230 PCPs, 1 had a readmission rate that was significantly higher than the mean and none had a significantly lower rate. The 10th and 90th percentiles of PCP readmission rates were 12.4% and 13.4%, respectively, each only 0.5 percentage point different from the mean. The 99th percentile of PCP readmission rates was 14.0%, 1.1 percentage points higher than the mean. Detecting a 1.1-percentage point difference from the mean adjusted readmission rate would require more than 3500 admissions per PCP per year. Limitations: Only fee-for-service Medicare patients in a single state were included. The authors could not account for confounders not included in Medicare databases or classify readmissions as avoidable. Conclusion: Variation in readmission rates among PCPs is very low. Programs holding PCPs accountable for readmissions may prove ineffective. Primary Funding Source: National Institutes of Health.

Housing discrimination and racial cancer disparities among the 100 largest US metropolitan areas.

BACKGROUND: Cancer contributes substantially to the life expectancy gap between US blacks and whites, and racial cancer disparities remain stubborn to eradicate. Disparities vary geographically, suggesting that they are not inevitable. METHODS: The authors examined the relationship between housing discrimination and the size of cancer disparities across large US metropolitan statistical areas (MSAs). MSA-level cancer disparities were measured using data from the US Centers for Disease Control and Prevention. Mortgage discrimination for each MSA was estimated using the Home Mortgage Disclosure Act database, and MSA racial segregation was determined using US Census data. Patterns of housing discrimination and cancer disparities were mapped, and the associations between these place-based factors and cancer disparities across MSAs were measured. RESULTS: Black-to-white cancer mortality disparities (rate ratios) varied geographically, ranging from 1.50 to 0.86; 88% of mortality ratios were >1, indicating higher mortality for blacks. In areas with greater mortgage discrimination, the gap between black and white cancer mortality rates was larger (correlation coefficient [r] = 0.32; P = .001). This relationship persisted in sex-specific analyses (males, r = 0.37; P < .001; females, r = 0.23; P = .02) and in models controlling for confounders. In contrast, segregation was inconsistently associated with disparities. Adjusting for incidence disparities attenuated, but did not eliminate, the correlation between mortgage discrimination and mortality disparities (r = 0.22-0.24), suggesting that cancer incidence and survival each account for part of the mortality disparity. CONCLUSIONS: Mortgage discrimination is associated with larger black-to-white cancer mortality disparities. Some areas are exceptions to this trend. Examination of these exceptions and of policies related to housing discrimination may offer novel strategies for explaining and eliminating cancer disparities.

The association of pharmacy fill synchronization with breast cancer endocrine therapy adherence.

BACKGROUND: One-third to one-half of patients prescribed adjuvant endocrine therapy are nonadherent during the recommended 5-year endocrine therapy course. This study investigated whether poor pharmacy synchronization of medication fills (requiring refills on different days) acts as a barrier to adherence. METHODS: A cohort of older women with stage 0 to III endocrine receptor-positive breast cancer in 2011 was identified from the Surveillance, Epidemiology, and End Result-Medicare claims-linked cancer registry. Women with endocrine therapy and at least 1 other medication fill were identified, and the 3-month synchronization of their fills was calculated as 1 minus the quotient of the number of pharmacy visits and the number of filled medications. Regression models were used to examine the association between synchronization (in quartiles adjusted for the number of medications) and adherence to endocrine therapy (defined as a medication possession ratio ≥80%) over the subsequent year. RESULTS: During the 3 months after the first endocrine therapy prescription, the study cohort of 3212 women had a mean of 8.6 pharmacy visits (standard deviation, 4.7) with a mean synchronization of 0.3 (standard deviation, 0.2). Those in the third (odds ratio, 1.29; 95% confidence interval, 1.04-1.59) and fourth (most) medication number-adjusted synchronization quartiles (odds ratio, 1.49; 95% confidence interval, 1.19-1.86) were more likely to be adherent than those in the least. Multivariate model predictions showed that the proportion of patients who were adherent over 1 year varied from 68.9% in the least synchronized quartile to 76.6% in the most synchronized one. CONCLUSIONS: Prescription refill synchronization is strongly associated with adherence to endocrine therapy. Efforts to improve adherence should address this.

Temporal trends and regional variation in the utilization of low-value breast cancer care: has the Choosing Wisely campaign made a difference?

PURPOSE: Since 2012, about 80 specialty societies have released Choosing Wisely (CW) recommendations aimed at reducing the use of low-value, unproven, or ineffective medical services. The extent to which these recommendations have influenced the behavior of physicians and patients remains largely unknown. METHODS: Using MarketScan Commercial Claims and Medicare Supplemental and Coordination of Benefits databases, we identified annual cohorts of women with incident, early-stage breast cancer and estimated the prevalence of four initial treatment and six surveillance metrics deemed as low-value breast cancer care by CW. Multivariable logistic regressions were subsequently used to estimate temporal trends and regional variation in the use of these metrics, with a special focus on the year of CW's publication. RESULTS: There were 122,341 women identified as undergoing treatment for incident breast cancer between 2010 and 2014. Two of the four low-value initial treatment metrics and four of the six low-value surveillance metrics declined significantly over time. The temporal trend of declining use, however, preceded the release of CW's guidelines. Declines ranged from 11.0% for follow-up mammography to 40.6% for receipt of surgical biopsy without an attempted needle biopsy. There were marked regional differences in use of low-value breast cancer care for all metrics, much of which persisted after publication of CW. CONCLUSIONS: With two notable exceptions, use of low-value breast cancer care has declined steadily since 2010. The declines, however, were not accelerated by the publication of CW recommendations.

The relationship between patient and tumor characteristics, patterns of breast cancer care, and 5-year survival among elderly women with incident breast cancer.

PURPOSE: To examine the relationship between patient and tumor characteristics, patterns of breast cancer care, and 5-year survival among a population-based cohort of elderly women with incident breast cancer, with a special focus on identifying sources of socioeconomic (SES) disparities in outcomes. METHODS: We identified women with newly diagnosed breast cancer in 2006-2009 from the Surveillance and Epidemiology End Result study linked with Medicare claims. A Classification and Regression Tree (CART) model was applied to 13 individual indicators of neoadjuvant and adjuvant breast cancer treatment, tumor characteristics, and patient sociodemographic variables to identify patterns with the greatest discriminant value in predicting 5-year survival. We subsequently examined the extent to which these patterns varied by the patient's SES. RESULTS: Survival probabilities associated with the 18 unique CART-identified patterns ranged from 22 to 87%. The number of positive axillary nodes was the best single discriminator between high and lower survival outcomes. The most common discriminant factor among patterns with poor (< 25%) survival was the absence of radiation treatment, followed by the presence of comorbidities, tumor size > 2 cm, and no breast surgery. Relative to high SES women, poor women were nearly four times (12.3% vs. 3.2%, p < 0.001) as likely to be classified in the pattern associated with worse survival, and less likely (31.7% vs. 52.9%, p = 0.04) to receive the pattern associated with the greatest survival. CONCLUSIONS: Greater adoption of effective patterns of care could improve survival of elderly women with incident breast cancer overall, and reduce SES disparities therein.

Socioeconomic status and breast cancer treatment.

PURPOSE: Evidence suggests substantial disparities in breast cancer survival by socioeconomic status (SES). We examine the extent to which receipt of newer, less invasive, or more effective treatments-a plausible source of disparities in survival-varies by SES among elderly women with early-stage breast cancer. METHODS: Multivariate regression analyses applied to 11,368 women (age 66-90 years) identified from SEER-Medicare as having invasive breast cancer diagnosed in 2006-2009. Socioeconomic status was defined based on Medicaid enrollment and level of poverty of the census tract of residence. All analyses controlled for demographic, clinical health status, spatial, and healthcare system characteristics. RESULTS: Poor and near-poor women were less likely than high SES women to receive sentinel lymph node biopsy and radiation after breast-conserving surgery (BCS). Poor women were also less likely than near-poor or high SES women to receive any axillary surgery and adjuvant chemotherapy. There were no significant differences in use of aromatase inhibitors (AI) between poor and high SES women. However, near-poor women who initiated hormonal therapy were more likely to rely exclusively on tamoxifen, and less likely to use the more expensive but more effective AI when compared to both poor and high SES women. CONCLUSIONS: Our results indicate that SES disparities in the receipt of treatments for incident breast cancer are both pervasive and substantial. These disparities remained despite women's geographic area of residence and extent of disease, suggesting important gaps in access to effective breast cancer care.

Prevalence and Consequences of Axillary Lymph Node Dissection in the Era of Sentinel Lymph Node Biopsy for Breast Cancer.

BACKGROUND: Despite clear guidelines for its use and wide adoption, no population-based study has examined the extent to which patients with early stage breast cancer are benefiting from sentinel lymph node biopsy (SLNB) by being spared a potentially avoidable axillary lymph node dissection (ALND) and its associated morbidity. OBJECTIVE: Examine variation in type of axillary surgery performed by surgeon volume; investigate the extent and consequences of potentially avoidable ALND. RESEARCH DESIGN/SUBJECTS: Observational study of older women with pathologically node-negative stage I-II invasive breast cancer who underwent surgery in a SEER state in 2008-2009. MEASURES: Surgeon annual volume of breast cancer cases and type of axillary surgery were determined by Medicare claims. An estimated probability of excess lymphedema due to ALND was calculated. RESULTS: Among 7686 pathologically node-negative women, 49% underwent ALND (either initially or after SLNB) and 25% were operated on by low-volume surgeons. Even after adjusting for demographic and tumor characteristics, women treated by higher volume surgeons were less likely to undergo ALND [medium volume: odds ratio, 0.69 (95% confidence interval, 0.51-0.82); high volume: odds ratio, 0.59 (95% confidence interval, 0.45-0.76)]. Potentially avoidable ALND cases were estimated to represent 21% of all expected lymphedema cases. CONCLUSIONS: In this pathologically node-negative population-based breast cancer cohort, only half underwent solely SLNB. Patients treated by low-volume surgeons were more likely to undergo ALND. Resources and guidelines on the appropriate training and competency of surgeons to assure the optimal performance of SLNB should be considered to decrease rates of potentially avoidable ALND and lymphedema.

Effect of hospital volume on processes of breast cancer care: A National Cancer Data Base study.

BACKGROUND: The purpose of this study was to examine variations in delivery of several breast cancer processes of care that are correlated with lower mortality and disease recurrence, and to determine the extent to which hospital volume explains this variation. METHODS: Women who were diagnosed with stage I-III unilateral breast cancer between 2007 and 2011 were identified within the National Cancer Data Base. Multiple logistic regression models were developed to determine whether hospital volume was independently associated with each of 10 individual process of care measures addressing diagnosis and treatment, and 2 composite measures assessing appropriateness of systemic treatment (chemotherapy and hormonal therapy) and locoregional treatment (margin status and radiation therapy). RESULTS: Among 573,571 women treated at 1755 different hospitals, 38%, 51%, and 10% were treated at high-, medium-, and low-volume hospitals, respectively. On multivariate analysis controlling for patient sociodemographic characteristics, treatment year and geographic location, hospital volume was a significant predictor for cancer diagnosis by initial biopsy (medium volume: odds ratio [OR] = 1.15, 95% confidence interval [CI] = 1.05-1.25; high volume: OR = 1.30, 95% CI = 1.14-1.49), negative surgical margins (medium volume: OR = 1.15, 95% CI = 1.06-1.24; high volume: OR = 1.28, 95% CI = 1.13-1.44), and appropriate locoregional treatment (medium volume: OR = 1.12, 95% CI = 1.07-1.17; high volume: OR = 1.16, 95% CI = 1.09-1.24). CONCLUSIONS: Diagnosis of breast cancer before initial surgery, negative surgical margins and appropriate use of radiation therapy may partially explain the volume-survival relationship. Dissemination of these processes of care to a broader group of hospitals could potentially improve the overall quality of care and outcomes of breast cancer survivors. Cancer 2017;123:957-66. © 2016 American Cancer Society.

Socioeconomic Disparities in Mortality Among Women With Incident Breast Cancer Before and After Implementation of Medicare Part D.

BACKGROUND: Breast cancer patients exhibit survival disparities based on socioeconomic status (SES). Disparities may be attributable to access to expensive oral endocrine agents. OBJECTIVES: Define recent socioeconomic disparities in breast cancer survival and determine whether these improved after implementation of the Medicare Part D program. DESIGN: Difference-in-difference natural experiment of women diagnosed and treated before or after implementation of Medicare Part D. SUBJECTS: Female Medicare beneficiaries with early-stage breast cancer: 54,772 diagnosed in 2001 and 46,371 in 2007. MEASURES: SES was based on Medicaid enrollment and zip code per capita income, all-cause mortality from Medicare, and cause of death from National Death Index. RESULTS: Among women diagnosed pre-Part D, 40.5% of poor beneficiaries had died within 5 years compared with 20.3% of high-income women (P<0.0001). Post-Part D, 33.6% of poor women and 18.4% of high-income women died by 5 years. After adjustment for potential confounders, improvement in all-cause mortality post-Part D was greater for poorer women compared with more affluent women (P=0.002). However, absolute improvement in breast cancer-specific mortality was 1.8%, 1.2%, and 0.8% (P=0.88 for difference in improvement by SES), respectively for poor, near-poor, and high-income women, whereas analogous improvement in mortality from other causes was 5.1%, 3.8%, and 0.9% (P=0.067 for difference in improvement by SES). CONCLUSIONS: Large survival disparities by SES exist among breast cancer patients. The Part D program successfully ameliorated SES disparities in all-cause mortality. However, improvement was concentrated in causes of death other than breast cancer, suggesting remaining gaps in care.

Geographic Variation of Adjuvant Breast Cancer Therapy Initiation in the United States: Lessons From Medicare Part D.

Background: Drug utilization under Medicare Part D varies significantly by geographic region. This study examined the extent to which geographic variation in Part D plan characteristics contributes to the variation in choice of initial endocrine therapy agent among women with incident breast cancer. Methods: Two-stage multivariate regression analyses were applied to the 16,541 women identified from Medicare claims as having incident breast cancer in 2006-2007. The first stage determined the effect of state of residence on the probability of having an aromatase inhibitor (AI), as opposed to tamoxifen, as initial endocrine therapy. The second stage provided estimates of the impact of state-specific Part D plan characteristics on variation in choice of initial therapy. Results: There was substantial residual geographic variation in the likelihood of using an AI as initial endocrine therapy, despite controlling for socioeconomic status, breast cancer treatment, and other factors. Regression-adjusted probabilities of starting an AI ranged from 57.3% in Wyoming to 92.6% in the District of Columbia. Results from the second stage revealed that variation in characteristics of Part D plans across states explained approximately one-third (30%) of the state-level variability in endocrine therapy. A higher number of plans with cost-sharing above the mean, greater spread in deductibles, and a greater spread in monthly drug premiums were associated with lower adjusted state probabilities of initiating an AI. In contrast, a higher number of drug plans with monthly premiums above the state mean and higher mean cost-sharing (in dollars) were both positively associated with likelihood of starting on an AI. Conclusions: Study findings suggest that variation in benefit design of Part D plans accounts for an important share of the large and persisting variability in use of AIs-the preferred oral therapy for breast cancer.

Breast Cancer Screening and Prevention.

This issue provides a clinical overview of breast cancer screening and prevention, focusing on risk assessment, screening, prevention, and practice improvement. The content of In the Clinic is drawn from the clinical information and education resources of the American College of Physicians (ACP), including MKSAP (Medical Knowledge and Self-Assessment Program). Annals of Internal Medicine editors develop In the Clinic in collaboration with the ACP's Medical Education and Publishing divisions and with the assistance of additional science writers and physician writers.

Perceived Neighborhood Quality and Cancer Screening Behavior: Evidence from the Survey of the Health of Wisconsin.

Socioeconomic disparities in colorectal and breast cancer screening persist, partially accounting for disparities in cancer outcomes. Some neighborhood characteristics--particularly area level socioeconomic factors--have been linked to cancer screening behavior, but few studies have examined the relationship between perceived neighborhood quality and screening behavior, which may provide more insight into the ways in which neighborhood environments shape cancer related behaviors. This study examines the relationship between several aspects of the perceived neighborhood environment and breast and colorectal cancer screening behavior among a population-based sample of Wisconsin residents. A sub-goal was to compare the relevance of different perceived neighborhood factors for different screening tests. This is a cross-sectional study of 2008-2012 data from the Survey of the Health of Wisconsin, a population-based annual survey of Wisconsin residents. An average risk sample of Black, Hispanic and White women age 50 and older (n = 1265) were selected. Survey regression analyses examined predictors of screening, as well as adherence to screening guidelines. Models controlled for individual socio-demographic information and insurance status. Perceptions of social and physical disorder, including fear of crime and visible garbage, were associated with screening rates. Findings emphasize the particular importance of these factors for colorectal cancer screening, indicating the necessity of improving screening rates in areas characterized by social disorganization, crime, and physical disorder. Additional work should be done to further investigate the pathways that explain the linkage between neighborhood conditions, perceived neighborhood risks and cancer screening behavior.

Breast and Colorectal Cancer Survival Disparities in Southeastern Wisconsin.

BACKGROUND: Cancer health disparities by race, ethnicity, socioeconomic status, and geography are a top public health priority. Breast and colorectal cancer, in particular, have been shown to exhibit significant disparities and contribute a large proportion of morbidity and mortality from cancer. In addition, breast and colorectal cancer offer targets for prevention and control, including nutrition, physical activity, screening, and effective treatments to prolong and enhance the quality of survival. However, despite the investment of significant time and resources over many years, breast and colorectal cancer disparities persist, and in some cases, may be growing. METHODS: This paper examines breast and colorectal cancer survival disparities in an 8-county region in southeastern Wisconsin, including the City of Milwaukee. Cox proportional hazards models were used to examine survival trends, and a new adaptation of adaptive spatial filtering--a disease mapping method--was used to examine spatial patterns of survival. RESULTS: Disparities by race and ethnicity are revealed, and spatial analyses identify specific areas within the study region that have lower than expected survival rates. CONCLUSIONS: Cancer control efforts in southeastern Wisconsin should focus on black/African American and Hispanic/Latina women to reduce breast cancer survival disparities, and black/African American populations to reduce colorectal cancer disparities. Evidence indicates that targeted interventions may be needed to serve populations in the Milwaukee and Kenosha metropolitan areas, as well as areas of Walworth, Ozaukee, and Waukesha counties.

Identifying patterns of breast cancer care provided at high-volume hospitals: a classification and regression tree analysis.

There is a growing body of literature linking hospital volume to outcomes in breast cancer. However, the mechanism through which volume influences outcome is poorly understood. The purpose of this study was to examine the relationship between hospital volume of breast cancer cases and patterns of processes of care in a population-based cohort of Medicare patients. A previously described and validated algorithm was applied to Medicare claims for newly diagnosed breast cancer cases in 2003 to identify potential subjects. Breast cancer patients were recruited to participate in a survey study examining breast cancer outcomes, and data were merged with Medicare claims and state tumor registries. Hospital volume was divided into tertiles. A Classification and Regression Tree (CART) model was performed to look for statistically significant relationships between patterns of processes of care and hospital volume. Using CART analysis, eight patterns of care were identified that differentiated breast cancer care at high- versus low-volume hospitals. Sentinel lymph node dissection (SLND) was the single process of care that demonstrated the greatest differentiation across hospitals with differing volumes. Four patterns of care significantly predicted that a patient was less likely to be treated at a high-volume hospital. Our study demonstrates differences in patterns of processes of care between low- and high-volume hospitals. Hospital volume was associated with several patterns of care that reflect the most current standards of care, particularly SLND. Greater adoption of these patterns by low-volume hospitals could improve the overall quality of care for breast cancer.