Comparing the ability of clinicians and a nomogram model at predicting future 99mTc-bone scan (BS) positivity in patients (pts) with rising prostate-specific antigen (PSA) following radical prostatectomy (RP) for prostate cancer (PCa).

Abstract

4652 Background: Nomograms that assist clinicians in predicting which PCa pts have a high risk of developing M1 disease have been developed, but clinicians still tend to use their own judgment of risk when managing individual pts. This is the first study to compare the ability of clinicians vs a nomogram at predicting future BS positivity in pts with PCa. Only androgen deprivation therapy- (ADT-) naive post-RP pts were considered, as there are currently no nomograms for predicting M1 disease in pts receiving ADT. The Slovin nomogram (Slovin et al. Clin Cancer Res 2005; 11: 8669-8673) was chosen based on considerations of the numbers of pts analyzed and the follow-up intervals used in its development. Methods: During an advisory board in June 2011, 24 PCa experts were given details of 25 ADT-naive post-RP PCa pts with biochemical recurrence who were randomly selected from the Cleveland Clinic Database of 759 pts. The predicted 1-yr from today probability of freedom from metastasis was generated using the Slovin nomogram and estimated by the clinicians. The predictive accuracy was quantified using the concordance index (C-index). Results: All pts were Caucasian and median age was 62 yrs. Median PSA level at biochemical recurrence was 1.2 ng/mL and PSADT varied between 1.3 and 11.7 months. The data used for each of the pts was acquired between 4 and 133 months after the RP procedure. Eight pts had a positive BS within 1 yr. Considerable variation between the clinicians’ predictions for each pt was observed. The nomogram gave a higher C-index compared to the clinicians (0.812 and 0.628, respectively; p=0.003). The clinicians typically overestimated the risk of developing M1 disease. The nomogram outperformed all of the clinicians (C-index range: 0.47 to 0.75). Urologists predictions were superior to those of oncologists (p=0.048). Conclusions: The Slovin nomogram was more accurate than expert clinicians in predicting 1-yr BS positivity. We suggest nomograms should become an integral part of the clinical decision process in the PCa setting.