Development of a nomogram model predicting current bone scan positivity in patients treated with androgen-deprivation therapy for prostate cancer.
OBJECTIVE
To develop a nomogram predictive of current bone scan positivity in patients receiving androgen-deprivation therapy (ADT) for advanced prostate cancer; to augment clinical judgment and highlight patients in need of additional imaging investigations.


METHODS
A retrospective chart review of bone scan records (conventional (99m)Tc-scintigraphy) of 1,293 patients who received ADT at the Memorial Sloan-Kettering Cancer Center from 2000 to 2011. Multivariable logistic regression analysis was used to identify variables suitable for inclusion in the nomogram. The probability of current bone scan positivity was determined using these variables and the predictive accuracy of the nomogram was quantified by concordance index.


RESULTS
In total, 2,681 bone scan records were analyzed and 636 patients had a positive result. Overall, the median pre-scan prostate-specific antigen (PSA) level was 2.4 ng/ml; median PSA doubling time (PSADT) was 5.8 months. At the time of a positive scan, median PSA level was 8.2 ng/ml; 53% of patients had PSA <10 ng/ml; median PSADT was 4.0 months. Five variables were included in the nomogram: number of previous negative bone scans after initiating ADT, PSA level, Gleason grade sum, and history of radical prostatectomy and radiotherapy. A concordance index value of 0.721 was calculated for the nomogram. This was a retrospective study based on limited data in patients treated in a large cancer center who underwent conventional (99m)Tc bone scans, which themselves have inherent limitations.


CONCLUSIONS
This is the first nomogram to predict current bone scan positivity in ADT-treated prostate cancer patients, providing high predictive accuracy.
Southern Alberta Institute of Urology, University of Calgary , Calgary, AB , Canada.
Geoffrey T
GT
Gotto
Department of Quantitative Health Sciences, Cleveland Clinic Foundation , Cleveland, OH , USA.
Changhong
C
Yu
Urology Service, Department of Surgery, Memorial Sloan Kettering Cancer Center , New York, NY , USA.
Melanie
M
Bernstein
Urology Service, Department of Surgery, Memorial Sloan Kettering Cancer Center , New York, NY , USA.
James A
JA
Eastham
Department of Quantitative Health Sciences, Cleveland Clinic Foundation , Cleveland, OH , USA.
Michael W
MW
Kattan
androgen-deprivation therapy; bone scan positivity; nomogram; non-steroidal anti-androgens; prostatic neoplasms; radionuclide imaging