Variation in the use of intensity-modulated radiation therapy (IMRT) in the state of Michigan: 2005-2010.

Abstract

219 Background: Interest is growing in value in health care, defined as better outcomes at lower costs. A primary driver of cost in radiation oncology is the use of IMRT. We examined the patterns and correlates of use of IMRT across Michigan using publicly available data. Methods: As a certificate of need state, Michigan requires every radiation oncology facility to report yearly the number of external beam and IMRT treatments delivered. Data for 2005-2008 were obtained through a Freedom of Information Act request of the Michigan Department of Community Health, while 2009-2010 data were available at its website. Percentage of external beam treatments delivered using IMRT (IMRT%) was examined across centers over time and repeated-measures longitudinal linear regression was used to identify factors associated with use. Results: During 2005-2010, 48 to 65 centers reported data. Median IMRT% (range) rose steadily during the study period: 2005 16% (0-64); 2006 21% (0-57); 2007 27% (0-79); 2008 37% (7-85); 2009 41% (0-87) 2010 45% (7-100). There was also significant between-center variation (see table). Regression modeling demonstrated that IMRT% was associated with year (+6.7% per year, p<0.0001), facility type (+7.1% freestanding versus hospital, p<0.11), facility annual volume (+5.0% high volume: 7,000+ versus low: <7,000, p=0.01) and the interaction between year and volume (low volume +2.4% per year versus high volume p<0.02). The significant interaction between year and volume suggests that the greatest IMRT% growth was in low volume centers (6.7% per year versus 4.3% per year for high volume). Conclusions: IMRT utilization has grown steadily across Michigan between 2005 and 2010. There is significant variation in its use that appears to be related in part to facility characteristics. The newly established Michigan Radiation Oncology Quality Collaborative (MROQC) is beginning to explore the use of IMRT in patients with breast and lung cancer statewide to identify those groups of patients where improved outcomes may justify its higher cost. [Table: see text]