Results
Table 1 compares patient demographics between the two cohorts. By the nature of age-based eligibility requirements, Medicare patients were older at diagnosis (mean age 75 vs 64 in i3 men). The predominant race in both Medicare and i3 patients was Caucasian. A plurality of patients in both cohorts resided in southern states. As expected, given the age distribution, i3 patients received surgery at a higher proportion than Medicare patients, whereas Medicare patients received more radiation.
Figure 1a and b depict the temporal trends in the type of primary treatment between each cohort. In the i3 population, the use of RP increased over time from 33% in 2002 to 48% by 2006; the use of EBRT remained stable at ~20%. Of those undergoing RP, only 0.8% had minimally invasive surgery (that is, laparoscopic/robotic) in 2002, which had increased to 40.8% by 2006. Despite the use of EBRT remaining stable, there was an increase in the use of IMRT from 21.8 to 71.1% during this time period. The use of BT remained stable at ~10% in the i3 cohort. Conversely, the use of RP (~12%) and EBRT (~31%) in the Medicare cohort remained stable during the study period. Similar to the i3 cohort, the utilization of minimally invasive surgery (0–35%) and IMRT (0–74.8%) increased in the Medicare sample from 1998 to 2006. There was an increase in the use of BT in Medicare patients from 4.6 to 12.6% over time. In both cohorts there was a decrease in the utilization of WW/AS; however, this was more pronounced in the i3 cohort. There was a decreased use of PADT in both cohorts. There was also limited utilization of newer radiation technologies such as cyberknife and proton beam therapy in both cohorts.
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Figure 1.
(a) Variation in primary treatment of prostate cancer over time in the i3 registry. (b) Variation in primary treatment of prostate cancer over time in the Medicare sample.
Variation in the use of neoadjuvant/adjuvant (neo/adjuvant) ADT around the time of primary prostate cancer treatment was observed between the Medicare and i3 cohorts over time (Figure 2). In general, men in i3 received neo/adjuvant ADT at a lower proportion than men in Medicare, regardless of the type of primary treatment (that is, RP, EBRT and cryotherapy). The use of neo/adjuvant ADT with primary EBRT reached its highest incidence in 2004, and then declined through the end of the study period in both cohorts. The use of neo/adjuvant ADT for RP, BT and cryotherapy declined over the entire study period.
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Figure 2.
(a) Variation in the use of neoadjuvant/adjuvant treatment in prostate cancer over time in the i3 registry. (b) Variation in the use of neoadjuvant/adjuvant treatment in prostate cancer over time in the Medicare sample.
Figure 3 shows the trends of adjuvant EBRT following RP over time in both i3 and Medicare cohorts. In both cohorts, the utilization of adjuvant radiation therapy is quite low; in Medicare it is ~6.5% and in i3 ~5%. There was an increasing trend in the use of adjuvant EBRT in the i3 men, whereas relatively stable incidence in Medicare men over time was observed. In the years directly comparable between Medicare and i3 (2002–2006), the trends differed the most between 2003 and 2004. During these years, incidence of adjuvant EBRT increased in i3 men and decreased in Medicare men.
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Figure 3.
Variation in the use of adjuvant external-beam radiation therapy following radical prostatectomy over time in both i3 and Medicare samples.
Figure 4 demonstrates the geographic variation in prostate cancer treatment (that is, RP, radiation therapy and primary ADT) by urologist and radiation oncologist density in three distinct regions of the United States: California, New England and Florida. Proportion receiving each treatment is categorized into quintiles, with lighter shades representing lower quintiles and darker shades higher quintiles. In New England, the counties with the highest urologist density had lower proportions receiving RP or PADT. Conversely, the counties with the highest density of radiation oncologist received higher proportions of radiation therapy. In California and Florida, there did not seem to be any discernable pattern between treatment received and urologist or radiation oncologist density. In the hierarchical multivariable analysis of those counties with at least 30 prostate cancer patients, age, comorbidity, urologist density, income level and year of diagnosis were significant predictors of the treatment (Table 2).
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Figure 4.
Geographic variation in prostate cancer treatment by urologist and radiation oncologist density in California, Florida and the Northeast.