National attention has focused on the impact of integrated urology/radiation oncology practice models on treatment choice for men with prostate cancer (PCa). We examined temporal treatment trends in Louisiana during a period in which an integrated prostate cancer center (IPCC) formed in a local health care market. Using data from the Surveillance, Epidemiology, and End Results (SEER) Program, we identified 10,945 men in Louisiana with non-metastatic PCa diagnosed between January 1, 2004 and December 31, 2007. We classified treatment according to SEER variables as external beam radiation therapy (EBRT), radical prostatectomy (RP), brachytherapy (BRT), combined external beam and brachytherapy (COMBO), or expectant management (EM). In June 2006, an IPCC was established in Shreveport-Bossier City, a health service area (HSA) with 3 pre-existing hospital-based radiotherapy centers. An HSA is defined as a cluster of contiguous counties which are self-contained with respect to hospital care. We examined differences in temporal treatment trends between Shreveport and the remaining 16 HSAs within Louisiana. We performed multivariable logistic regression with the outcome variable dichotomized as EBRT vs other treatment, adjusted for HSA, diagnosis year, AJCC stage, Gleason sum, age, race, marital status, and the interaction of HSA with year. In the Shreveport-Bossier City HSA, EBRT use increased 15.1% (from 18.3% of men in 2004 to 33.4% of men in 2007), RP use increased 3.4% (37.2% to 40.6%), BRT declined 3.9% (6.3% to 2.4%), COMBO declined 0.4% (0.8% to 0.4%), and EM declined 14.1% (37.4% to 23.3%). In the remaining HSAs in Louisiana, EBRT use increased 3.4% (16.6% to 20.0%), RP use increased 2.7% (33.7% to 36.4%), BRT declined 2.3% (12.1% to 9.8%), COMBO decreased 0.3% (3.1% to 2.8%), and EM declined 3.5% (34.5% to 30.9%). Relative to the remaining HSAs in Louisiana, EBRT use in Shreveport increased by an additional 11.7%. In multivariable regression, the differential increase in EBRT between Shreveport and the remaining HSAs in Louisiana was significant (p = 0.03 for interaction of HSA with year). Other characteristics significantly associated with a higher likelihood of EBRT included stage T3 (p<0.001), Gleason 8-10 (p = 0.006), age > 55 years (p<0.001), and black race (p = 0.004). In Louisiana between 2004 and 2007, EBRT increased more than RP, and other treatments declined. EBRT increased more dramatically in an HSA in which an IPCC was established, largely at the expense of expectant management. However, further research is required to disentangle whether the observed treatment patterns result from integrated practice models, the opening of a new free-standing facility, or other important unmeasured factors.