Determinants of androgen deprivation therapy use for prostate cancer: role of the urologist

Abstract

Background: The use of androgen deprivation therapy for prostate cancer has been increasing, even in settings for which there is weak or no evidence of efficacy. This pattern suggests that factors other than the typical patient and tumor characteristics may be driving its use. We assessed the importance of the physician as a determinant of the use of androgen deprivation therapy in prostate cancer in a population-based, retrospective cohort study using the Surveillance, Epidemiology and End-Results-Medicare linked database.

Methods: Participants included 61 717 men with incident prostate cancer diagnosed from January 1, 1992, through December 31, 1999, and 1802 urologists providing care to them within 1 year of cancer diagnosis. Multilevel analyses were used to estimate and partition the variance in use of androgen deprivation therapy within 6 months of diagnosis between patient or tumor characteristics and urologist to examine the relative contribution of each component to androgen deprivation therapy.

Results: The percentage of the total variance in the use of androgen deprivation therapy attributable to the urologist was consistently higher than that attributable to tumor or patient characteristics. This pattern was most pronounced for patients diagnosed from January 1, 1997, through December 31, 1999, in which 22.56% of the total variance in use of androgen deprivation therapy was attributable to the urologist, 9.71% to tumor characteristics (stage or grade), and 4.29% to patient characteristics (age, ethnicity, socio-economic status, comorbidity, geographic region, or year of diagnosis).

Conclusions: Which urologist a patient sees may be more important in determining whether they will receive androgen deprivation therapy than tumor or patient characteristics.

Fig. 1

Rates of androgen deprivation therapy use for 153 individual urologists by rank, from lowest to highest, who cared for patients in the evidence-based group diagnosed with prostate cancer from 1997 through 1999. The rates were calculated by use of hierarchical generalized linear modeling, adjusted for patient and tumor characteristics. This model also accounts for differences in reliability of individual rates resulting from variations in the size of the panel of patients for each urologist. Each urologist-specific rate was therefore adjusted toward the mean of the overall rate as a factor of panel size (i.e., a urologist rate that is based on a large panel of patients will result in very little adjustment toward the mean rate, whereas a urologist rate that is based on a small panel will have more adjustment). This analysis was limited to urologists who saw at least five patients. The horizontal line represents the overall mean rate of androgen deprivation. Error bars represent 95% confidence intervals for the rates of individual urologists. Black error bars represent urologists that have rates statistically significantly (P value range = <.001 to .045) below the mean rate, dark gray bars represent urologists that have rates statistically significantly above the mean rate (P value range = .009 to .025), and light gray bars represent rates that are not different from the mean rate.

Fig. 2

Rates of androgen deprivation therapy use for 808 individual urologists by rank, from lowest to highest, who cared for patients in the uncertain-benefit group diagnosed with prostate cancer from 1997 through 1999. Rates were calculated by use of hierarchical generalized linear modeling, adjusted for patient and tumor characteristics. This model also accounts for differences in the reliability of individual rates resulting from variations in the size of the panel of patients for each urologist. Each urologist-specific rate was therefore adjusted toward the overall rate mean as a factor of panel size (i.e., a urologist rate that is based on a large panel of patients will result in very little adjustment toward the mean rate, whereas a urologist rate that is based on a small panel will have more adjustment). This analysis was limited to urologists who treated at least five patients. The horizontal line represents the overall mean rate of androgen deprivation. Error bars represent 95% confidence intervals for the rates of individual urologists. Black error bars represent urologists that have rates statistically significantly (P value range = <.001 to .049) below the mean rate, dark gray bars represent urologists that have rates statistically significantly above the mean rate (P value range = <.001 to .050), and light gray bars represent rates that are not different from the mean rate.