Shared-patient physician networks and their impact on the uptake of genomic testing in breast cancer

Background: Factors influencing the adoption of genomic testing are poorly understood, which may lead to inequitable and suboptimal treatment in cancer patients. Oncotype DX (ODX) is one of the first and most widely used genomic assays to stratify risk in women with early-stage breast cancer (BC). Physician networks have emerged as a significant and modifiable driver of emerging medical technology adoption. Objective: To investigate the association between physician network connections and the use of ODX testing. Methods: A retrospective study of women diagnosed with BC using SEER-Medicare from 2008 to 2012 was used. Medical oncologists were “connected” if they shared two or more patients during the early-adoption period (2008–2009). Parallel physician- and patient-level analyses employed logistic mixed models to determine the impact of being “connected” to an early-adopting oncologist on ODX use in 2011–2012. Results: 24,463 women met study criteria; 12,874 were diagnosed with BC in the early-adoption time period. 2129 medical oncologists treated these patients from 2008 to 2009. Medical oncologists had a median number of peer connections of 4 (IQR: 2–7). Peer connection to an early-adopting provider in 2008–2009 was associated with a 1.7-fold increase in providers’ adopting ODX (95% CI: 1.1–2.6) and a 1.5-fold increase in their patients receiving ODX (95% CI: 1.1–2.0) in 2010–2012. Conclusions: Peer connectedness to an early-adopting physician predicts ODX adoption in both physician-level and patient-level analyses. Provider networks may provide a potent and modifiable means to modulate the diffusion of emerging medical technologies. Efforts to increase testing, where appropriate, may benefit from peer-to-peer-based connection strategies.