Practice Patterns and Predictors of Followup Imaging after a Negative Bone Scan in Men with Castration Resistant Prostate Cancer: Results from the SEARCH Database

PurposeWe investigated imaging practice patterns in men with nonmetastatic (M0) castration resistant prostate cancer.Materials and MethodsWe analyzed data on 247 patients with documented M0 CRPC from the SEARCH database. Patients were selected regardless of primary treatment modality and all had a negative bone scan after a castration resistant prostate cancer diagnosis. Cox models were used to test associations of time to a second imaging test with several demographic and clinical factors.ResultsDuring a median followup of 29.0 months (IQR 12.9–43.5) after a post-castration resistant prostate cancer bone scan was negative, 190 patients (77%) underwent a second imaging test. On univariable analysis patients with higher prostate specific antigen (HR 1.13, p = 0.016), shorter prostate specific antigen doubling time (HR 0.79, p <0.001) and faster prostate specific antigen velocity (HR 1.01, p <0.001) were more likely to undergo a second imaging test. Treatment center was also a significant predictor of a second imaging test (p = 0.010). No other factor was a significant predictor. Results were similar on multivariable analysis. It was estimated that approximately 20% of men with a prostate specific antigen doubling time of less than 3 months did not undergo an imaging test in the first year after a post-castration resistant prostate cancer negative bone scan. However, 50% of patients with prostate specific antigen doubling time 15 months or greater underwent a second imaging test in the first year.ConclusionsClinicians use some known predictors of positive imaging tests to determine which patients with M0 castration resistant prostate cancer undergo a second imaging test . However, there may be under imaging in those at high risk and over imaging in those at low risk. Further studies are needed to identify risk factors for metastasis and form clear imaging guidelines in patients with M0 castration resistant prostate cancer.