Abstract
Purpose: 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.Materials and methods: A retrospective chart review of bone scan records (conventional 99mTc-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 99mTc bone scans, which themselves have inherent limitations.Conclusion: This is the first nomogram to predict current bone scan positivity in ADT-treated prostate cancer patients, providing high predictive accuracy.
Highlights
Between 15 and 40% of patients treated for localized prostate cancer will experience biochemical recurrence (BCR), as shown by rising prostate-specific antigen (PSA) levels [1]
Five variables were included in the nomogram: number of previous negative bone scans after initiating Androgendeprivation therapy (ADT), PSA level, Gleason grade sum, and history of radical prostatectomy and radiotherapy
The nomogram model presented in this study is the first analytical tool developed to predict current bone scan positivity in prostate cancer patients treated with ADT
Summary
Between 15 and 40% of patients treated for localized prostate cancer will experience biochemical recurrence (BCR), as shown by rising prostate-specific antigen (PSA) levels [1]. Castration-resistant prostate cancer (CRPC) is defined as disease progression, typically identified by rising PSA levels and/or worsening disease according to imaging, despite castration levels of testosterone; most patients with CRPC will eventually develop metastatic (M1) disease [3]. The axial skeleton is the most common site of systemic metastasis in patients with prostate cancer [4]. Bone imaging can provide important information on the clinical status of asymptomatic patients with rising PSA levels. Novel therapies, some of which provide benefits for patients with asymptomatic M1 CRPC, have recently been developed and approved [8, 9]
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