Study Identifies Patterns of Peer Pressure With Advanced Imaging in Breast Cancer

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A research study by scientists at Yale and Johns Hopkins has found that surgeons are influenced by their peers when it comes to the use of new imaging technologies.

A research study by scientists at Yale and Johns Hopkins has found that surgeons are influenced by the practice style of their peers when it comes to the use of new imaging technologies, such as magnetic resonance imaging (MRI) and positron emission tomography (PET), in patients with breast cancer.

Concerns over the use of unnecessary healthcare services resulted in the launch of the Choosing Wisely campaign in 2012 by the American Board of Internal Medicine Foundation (ABIM), which aimed to arm physicians with information that can help them be stewards of high-value services in their organization. Subsequently, several medical organizations partnered with ABIM to develop specific recommendations relevant to their specialty that can help providers avoid the use of low-value services.

One such recommendation by the American Society of Clinical Oncology, states:

Don’t perform PET, CT, and radionuclide bone scans in the staging of early breast cancer at low risk for metastasis.

The American Society of Brest Surgeons recommends:


Don’t routinely order breast MRI in new breast cancer patients.

Physician decision to provide care is often influenced by a combination of patient demand, clinical evidence, their personal preference, and health system factors. However, when it comes to the adoption of innovative technologies, physicians are often influenced by the “social contagion,” the authors wrote. The objective of the current study was to understand the factors that influence the use of these expensive imaging modalities in practice.

“Our study adds a new wrinkle to the literature. We found that physicians, like any other group of interconnected individuals, are also susceptible to the social influence of their physician peers,” Cary P. Gross, MD, professor of medicine and director of Yale’s Cancer Outcomes Public Policy and Effectiveness Research Center, said in a statement.

The analysis included a linked Surveillance, Epidemiology, and End Results—Medicare database to sort physicians into peer groups of those who shared patients during a baseline period when PET and MRI were starting to disseminate into practice (2004 to 2006). Their potential impact was estimated during a follow-up period (2007 to 2009). For surgeons whose patients did not receive MRI/PET during baseline (non-early adopters), the effect of their peer group’s baseline use on their use of MRI/PET during the follow-up period was examined.

The final sample for analysis included 1369 surgeons sorted across 296 peer groups who treated 14,542 women diagnosed with breast cancer during the baseline period and 12,549 diagnosed with breast cancer during the follow-up period.

For MRI, there were 6424 women diagnosed in the follow-up period assigned to 986 non-early-adopting surgeons. The authors observed the following:

  • During baseline, 9.3% of women received an MRI, varying across peer groups from 0% to 81%.
  • Women assigned to surgeons whose peers had the highest rate of baseline MRI use were more likely to receive MRI (24.9%) compared with women whose surgeons’ peers did not use MRI (10.1%; adjusted odds ratio [OR], 2.47; 95% CI, 1.39 to 4.39).
  • Physician peers were associated with uptake of PET imaging (OR for highest vs lowest baseline peer group PET use, 2.04; 95% CI, 1.24 to 3.36).

“Peer influence can be a conduit that helps to increase the use of medical approaches that are not based on sound evidence—or alternatively, this social contagion might also be used to promote best practices among physicians,” Gross said.


Pollack CE, Soulos PR, Herrin J, et al. The impact of social contagion on physician adoption of advanced imaging tests in breast cancer. J Natl Cancer Inst. 2017;109(8). doi: 10.1093/jnci/djw330.