Wide variation in the diffusion of a new technology: Practice-based trends in intensity-modulated radiation therapy (IMRT) use in the state of Michigan, with implications for IMRT use nationally

Purpose: To characterize the adoption and variation of intensity-modulated radiation therapy (IMRT) use in the state of Michigan. Methods: As a certificate-of-need state, Michigan requires every radiation oncology facility to report the number of externalbeam and IMRT treatments delivered annually. We examined the percentage of treatments delivered using IMRT across centers from 2005 to 2012. We constructed a repeated-measures longitudinal linear regression model to evaluate bivariable and multiple variable associations with IMRT use. Results: The median proportion of treatments delivered with IMRT rose from 16% in 2005 to 42% in 2012. All treatment centers in the state of Michigan possessed the capacity to deliver IMRT as of 2009. The fraction of treatments delivered with IMRT varied between 23% and 96% (standard deviation, 19%) in the lowest- and highest-use centers in 2012. Higher IMRT use was significantly associated with freestanding facilities and year of treatment, with a trend toward higher IMRT use in academic centers and low-volume facilities. Conclusion: IMRT use grew significantly across the state of Michigan over time, with four-fold variability among centers, which was related to facility characteristics. These data provide no indication of an ideal or appropriate level of IMRT use. Rather, the wide variation in IMRT use among centers indicates a lack of consensus regarding the situations in which IMRT provides significant clinical benefit. This supports further research and interventions to ensure that patients receive appropriate care, regardless of where they are treated.