Peer Influence May Lead to Subsequent Physician Adoption


In this study, researchers looked at the adoption and use of bevacizumab in order to identify opportunities to increase use of high-value therapies.

Oncologists’ adoption and use of bevacizumab (Avastin) in the years after its approval was greater if their peer physicians were earlier adopters, according to an investigation published in JAMA Network Open

As organizations continue to strive toward better care at lower costs, interventions that influence physician ties may help to promote adoption of high-value use of new cancer treatments and unemployment of low-value therapies.

“These findings offer a crucial new insight into why there may be large regional variations in physicians’ use of new therapies,” Damon Centola, PhD, said in an accompanying editorial. “They suggest that patterns of regional variation may be due to social norms within physicians’ local medical communities that endorse some treatment practices and prohibit others.” 

Starting in 2005 to 2006, researchers examined the prescription behavior of 829 oncologists across 432 practices and 405 distinct communities over the course of 4 years. Of the cohort of 44,012 patients in these communities, 34,750 patients with colorectal, lung, breast, kidney, ovarian, and brain cancer were treated with chemotherapy during 2005 to 2006 and 9,262 patients had never received treatment with bevacizumab before 2007.

The rate of bevacizumab (Avastin) use compared to other chemotherapy in 2007 to 2010 by tertile of use (bevacizumab for <4.4%, 4.4%-6.2%, and >6.2% of all patients receiving chemotherapy) among their physician’s peers in 2005 to 2006 was 10.0%, 9.5%, and 13.6%, respectively. After adjustment, the use of bevacizumab in 2007 to 2010 was greater among physicians in communities that had the highest rates of bevacizumab use in 2005 to 2006 relative to those whose peers were in the lowest tertile of bevacizumab use in 2005 to 2006 (adjusted odds ratio, 1.64; 95% CI, 1.20-2.25).

“This suggests that the adoption of bevacizumab is a complex contagion (i.e., needing social reinforcement) rather than a simple contagion (i.e., needing simple informational contact only),” the authors wrote.

With the expansion of new oncologic therapies, many of which have very high prices and modest or limited benefits, it is increasingly important for policy makers to ensure that physicians are influenced to deliver high-value care. Moreover, cancer drugs are frequently off label, where benefits may be less clear.

Current efforts to advance delivery of high-value care, such as the Oncology Care Model and other alternative payment models, target physician organizations, a method that partially relies on the development of practice norms that emerge in response to these incentives. 

However, physician behavior is difficult to change according to the researchers and understanding the physicians to target is crucial. “For example, academic detailing has potential to influence clinician behavior, especially if targeted to key opinion leaders who are perceived as influential experts by their peers,” the authors wrote. “Other evidence suggests that in decentralized networks, social influence can generate learning dynamics that improve the performance of the group, which could potentially slow adoption of low-value therapies or those lacking sufficient evidence.”

Given the complexity of this topic, future research is necessary, however this data yields unique information that sheds new light on the subject. 


1. Keating NL, O’Malley AJ, Onnela J, Gray SW, Landon BE. Association of Physician Peer Influence With Subsequent Physician Adoption and Use of Bevacizumab. JAMA Network Open. doi:10.1001/jamanetworkopen.2019.18586.

2. Centola D. Physician Networks and the Complex Contagion of Clinical Treatment. JAMA Network Open. doi:10.1001/jamanetworkopen.2019.18585.

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