title: The Impact of Social Contagion on Physician Adoption of Advanced Imaging Tests in Breast Cancer.
abstract: Magnetic resonance imaging (MRI) and positron emission tomography (PET) scans are widely used in breast cancer practice despite unproven benefits. We examined the extent to which social contagion is associated with adoption of these imaging modalities.
  
  
  
  We used Surveillance, Epidemiology, and End Results-Medicare to construct peer groups of physicians who shared patients during a baseline period when these imaging modalities were starting to disseminate into practice (2004-2006) and determined the potential impact of these peer groups during a follow-up period (2007-2009). For non-early-adopting surgeons (whose patients did not receive MRI/PET during baseline), we used hierarchical logistic regression models to examine the effect of their peer group's baseline use on their use of MRI/PET during the follow-up period, adjusting for patient characteristics and hospital MRI/PET use.
  
  
  
  For MRI, there were 6424 women diagnosed in the follow-up period assigned to 986 non-early-adopting surgeons. 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 compared with women whose surgeons' peers did not use MRI (24.9% vs 10.1%, adjusted odds ratio [OR] = 2.47, 95% confidence interval [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).
  
  
  
  The phenomenon of social contagion may offer opportunities to better understand how new approaches to cancer care disseminate into clinical practice.
authors.affiliation: Johns Hopkins School of Medicine, Baltimore, MD, USA.|Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
authors.forename: Craig E
authors.initials: CE
authors.lastname: Pollack
authors.affiliation: Cancer Outcomes, Public Policy and Effectiveness Research (COPPER) Center, Yale Cancer Center and Yale School of Medicine, New Haven, CT, USA.|Section of General Internal Medicine, Yale School of Medicine, New Haven, CT, USA.
authors.forename: Pamela R
authors.initials: PR
authors.lastname: Soulos
authors.affiliation: Cancer Outcomes, Public Policy and Effectiveness Research (COPPER) Center, Yale Cancer Center and Yale School of Medicine, New Haven, CT, USA.|Section of Cardiology, Yale School of Medicine, New Haven, CT, USA.|Health Research and Educational Trust, Chicago, Illinois, USA.
authors.forename: Jeph
authors.initials: J
authors.lastname: Herrin
authors.affiliation: Cancer Outcomes, Public Policy and Effectiveness Research (COPPER) Center, Yale Cancer Center and Yale School of Medicine, New Haven, CT, USA.|Department of Internal Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences, Yale School of Medicine, New Haven, CT, USA.
authors.forename: Xiao
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Sociology and Yale Institute for Network Science and Human Nature Lab Yale University, New Haven, CT, USA.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Christakis
authors.affiliation: Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, USA.
authors.forename: Howard P
authors.initials: HP
authors.lastname: Forman
authors.affiliation: Cancer Outcomes, Public Policy and Effectiveness Research (COPPER) Center, Yale Cancer Center and Yale School of Medicine, New Haven, CT, USA.|Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT, USA.
authors.forename: James B
authors.initials: JB
authors.lastname: Yu
authors.affiliation: Cancer Outcomes, Public Policy and Effectiveness Research (COPPER) Center, Yale Cancer Center and Yale School of Medicine, New Haven, CT, USA.|Department of Surgery, Yale School of Medicine, New Haven, CT, USA.|Yale Cancer Center, New Haven, CT, USA.
authors.forename: Brigid K
authors.initials: BK
authors.lastname: Killelea
authors.affiliation: Cancer Outcomes, Public Policy and Effectiveness Research (COPPER) Center, Yale Cancer Center and Yale School of Medicine, New Haven, CT, USA.|Department of Chronic Disease Epidemiology, Yale School of Public Health, New Haven, CT, USA.
authors.forename: Shi-Yi
authors.initials: SY
authors.lastname: Wang
authors.affiliation: Cancer Outcomes, Public Policy and Effectiveness Research (COPPER) Center, Yale Cancer Center and Yale School of Medicine, New Haven, CT, USA.|Section of General Internal Medicine, Yale School of Medicine, New Haven, CT, USA.
authors.forename: Cary P
authors.initials: CP
authors.lastname: Gross
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D033181:Information Dissemination / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D010379:Peer Group; D000067074:Peer Influence; D049268:Positron-Emission Tomography / Q000706:statistics & numerical data*; D010818:Practice Patterns, Physicians'; D012189:Retrospective Studies; D018426:SEER Program; D066231:Surgeons