Abstract P4-09-08: Shared-patient physician networks and their impact on the uptake of genomic testing in early-stage breast cancer
Authors: Rotter J , Wilson L , Greiner M , Pollack C , Dinan M 
Published: May 2019

Abstract
Background: Oncotype DX (ODX) or 21-gene recurrence score genomic testing is used to stratify risk and determine appropriate treatment in women with early-stage breast cancer (BC). Diffusion of ODX by way of physician networks has not been studied.
Objective: To determine the association between physician network connections, defined by shared patients, and the use of ODX testing.
Methods: SEER-Medicare claims from 2008-2012 were used to identify a cohort of woman with a diagnosis of BC from registry/ICD codes, continuously enrolled in Medicare fee-for-service Part A and B one year prior to and one year following diagnosis. We identify receipt of ODX from the associated CPT code, claim reimbursement, and performing NPI. To look at the influence of network connections on ODX use, we split the study into two time periods: early adoption from 2008-2009, and late from 2010-2012. Medical oncologists with a BC-related claim in the cohort above, and any rendered BC-related service are considered 'connected' if they shared two or more BC patients. Analyses describe these connections and explore the association between connectedness to an early adopting medical oncologist and ODX use in parallel physician and patient-level analyses using generalized linear mixed models with a hospital referral region-specific random effect. Models control for physician and patient-level characteristics where applicable.
Results:24,463 women met study criteria; 12,874 were diagnosed with BC in the early adoption time period (1,790 received ODX) and 11,589 were diagnosed in the late period (2,334 received ODX). 2,073 medical oncologists treated these patients from 2008-2009. The mean number of BC patients treated per medical oncologist was 86.8 during the early adoption period, and medical oncologists had a median number of peer connections of 11 (IQR: 7-18). Early adopting medical oncologists had higher numbers of peer connections and higher average patient counts than non-early adopters. A higher percentage of female medical oncologists were early adopters (39%) then male medical oncologists (33%) (p&lt;0.02). Among non-early adopting oncologists, peer connection to at least two early adopting providers in 2008-2009 is associated with a 3.2 (95% CI: 2.0-4.9) times increase in the odds of ordering ODX in 2010-2012 after adjustment for physician gender and time in practice. In patient-level models with controls for physician and patient characteristics, seeing a medical oncologist with connections to at least two early adopting physicians is associated with a 1.6 times (95% CI: 1.1-2.2) increase in the odds of receiving ODX testing in 2010-2012.
Conclusions: We observe a positive adjusted association between connectedness to an early-adopting physician and ODX prescribing/use in both physician-level and patient-level analyses. These results suggest that provider networks may help diffuse new technologies, and that BC genomic testing is likely to be an area of shared practices between providers. Efforts to increase testing, where appropriate, may benefit from a range of peer-to-peer connection strategies.
Citation Format: Rotter J, Wilson L, Greiner M, Pollack C, Dinan M. Shared-patient physician networks and their impact on the uptake of genomic testing in early-stage breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-09-08.