Editorial: Peer Influence and Opportunities for Physician Behavior Change

A large body of evidence demonstrates substantial area-level variations in intensity of care and health care spending in the United States. This variation is evident both across and within regions and exists for all types of care, including oncology care (1) and care identified to be of low value (2). Although the sources of variation have been long debated, recent evidence suggests that physicians’ beliefs, independent of organizational factors, are the key drivers in explaining area-level variations in health care spending (3). Physicians in the United States have substantial autonomy in decisions about care for patients, and thus their decisions are important drivers of health care utilization. Current alternate payment models target provider organizations in the hope that they create opportunities for physicians to influence and improve the value of care delivered by the organization. However, physician behavior is notoriously difficult to change, and relatively little evidence is available about the ability of physicians to directly influence the clinical decisions of their peers.

In this issue of the Journal, Pollack and colleagues used data from the Surveillance, Epidemiology, and End Results–Medicare program to assess the role of physician networks in explaining adoption of perioperative advanced imaging tests for women with breast cancer (4). In a creative analysis, they identified the operating surgeons for women diagnosed with nonmetastatic breast cancer during 2004 to 2009. They specified 2004 to 2006 as the baseline period, during which time magnetic resonance imaging (MRI) and positron emission tomography (PET), two tests with unproven benefits in this setting, were just being adopted. They characterized perioperative use of these tests for all surgeons in the baseline period and specifically identified surgeons who had not used one or the other test during that time. They next assigned each surgeon to a “peer group” or network of physicians who share patients and may thus communicate their beliefs and practice styles with each other. The peer groups were identified using methods from network science (5) that examined patient-sharing patterns of surgeons, medical oncologists, radiation oncologists, primary care physicians, and radiologists caring for breast cancer and noncancer patients. The authors hypothesized that among surgeons who did not use MRI or PET in the baseline period, those whose peer groups ordered more MRIs or PET scans during the baseline period would be more likely to adopt MRI or PET during the follow-up period (2007–2009). As predicted, women treated by surgeons whose peer physicians had the highest rates of MRI in the baseline period were more likely to receive MRI than women whose surgeons’ peers used fewer or no MRIs in the baseline period. Similarly, women in the follow-up period were more likely to undergo PET scans if their surgeons’ peers were in the highest category of baseline PET use, although if surgeons’ peers were in intermediate categories of baseline use, there was no association.

The increasing availability of rich encounter data from insurance claims has allowed researchers to identify physicians who are connected to each other by virtue of sharing patients. Physicians who interact in caring for patients are likely to share their experiences, beliefs, and ideas regarding clinical care. Such exchange of information has the potential to influence the practice patterns of their colleagues. Prior work has demonstrated that identifying relationships between physicians based on sharing of patients is a valid method for identifying meaningful relationships, such as advice seeking and giving/receiving referrals, between physicians, including primary care physicians, medical specialists, and surgical specialists (6).

An important consideration in interpreting the findings of this work is the extent to which peer effects can be distinguished from other contextual influences on a physician, such as a shared practice setting, shared financial incentives, use of common guidelines, and availability of new technologies. Although in this study data were not available regarding whether surgeons and other physicians in the peer groups worked in the same practice or attended tumor board or other meetings together, the authors attempted to address this concern by assigning each surgeon to a hospital and adjusting analyses for baseline levels of MRI or PET use at each surgeon’s hospital. Because surgeons’ practices are frequently hospital-based and because imaging is often available in hospitals, this is a reasonable approximation for identifying surgeons who practice together as well as the availability of new imaging technologies. Despite this adjustment, the association between surgeons’ peer groups and their likelihood of testing in the follow-up period persisted. In addition, the authors used a series of multilevel models to understand the proportion of variance explained by peer groups vs individual surgeons or hospitals. They found that peer groups accounted for variation that was not explained by hospitals or individual surgeons. These findings are consistent with other work suggesting that community-based networks of physicians such as those characterized by Pollack and colleagues reflect distinct constructs from hospital-based physician networks (7).

Another potential explanation for the findings by Pollack et al. (4) is that physicians tend to share patients with other physicians who are similar to them in terms of personal or practice characteristics and practice style. Such homophily has been previously documented in physician networks identified based on patient-sharing relationships (8). A strength of the current study is its linking of peer groups’ baseline use of MRI and PET to future adoption of these tests among surgeons who had not used them in the baseline period. One would expect that surgeons whose practice styles were most similar to baseline users would have also been using these tests in the baseline period.

The application of network methods has great potential to further our understanding of how physicians influence their peers. The findings by Pollack and colleagues (4) support the hypothesis that peer influence is a driver of physicians’ practice styles and raise the possibility that leveraging such influence may provide opportunities to limit the adoption and use of low-value care. Future work is needed to better understand the extent to which surgeon and other physician peer groups span local practice groups and how peer groups change over time, as well as whether there are important characteristics of peer groups or the physicians within them that are most influential and how these vary for different clinical scenarios. Research is also needed to identify the most effective strategies to leverage influential connections to promote physician behavior change. Identifying and studying the organizations that are most successful in alternate payment models, such as accountable care organizations and the Centers for Medicare and Medicaid Innovation Oncology Care Model, may provide additional insights into how physicians and other health care providers can work together to limit waste and provide better care at lower cost.

Funding

Dr. Keating has received funding from the National Cancer Institute to study the effects of physician networks and the spread of cancer care practices (1R01CA174468-01). She is also supported by K24CA181510 from the National Cancer Institute.

Notes

The funders had no role in the writing of the editorial or the decision to submit it for publication. The author has no conflicts of interest to disclose.