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Bone Scan Index as an imaging biomarker to predict overall survival in the Zeus/SPCG11 study.
Background: The Zeus/SPCG11 study is a randomized controlled clinical trial with the aim to assess the efficacy of zoledronic acid (ZA) in preventing bone metastases in high-risk prostate cancer (PCa) patients. Bone Scan Index (BSI) reflects the tumour burden in bone calculated from bone scintigraphy, and has recently been validated as an imaging biomarker in metastatic PCa patients. The purpose of this study was to investigate if change in BSI during treatment may serve as a useful imaging biomarker to predict clinical outcome in the Zeus/SPCG11 study population. Methods: We retrospectively selected as our BSI-study cohort all patients with bone scan image data of sufficient quality to allow for both baseline and 48-months follow-up BSI-assessments. BSI data was obtained by using the automated quantification software EXINI boneBSI, in a blind fashion, without knowledge of any clinical data or treatment randomization. Clinical data on age, overall survival (OS) and prostate-specific antigen (PSA) concentration in blood at baseline and upon follow-up was collected separately. Association between clinical data and BSI change during treatment was evaluated using Cox proportional-hazards regression models, Kaplan-Meier estimates of the survival function and Log rank test. Discrimination between prognostic variables was assessed using the concordance index (C-index). Results: The 176 patients who fulfilled the inclusion criteria presented showed baseline characteristics similar to those of the final total Zeus/SPCG11 study population (N = 1,433)(p= 0.83). In our BSI-study cohort (N = 176), patients with a BSI change < 0.3 had a significantly longer median survival time compared to patients with BSI increase of > 0.3 (32.3 months and 18.2 months respectively) (p < 0.001). In the Cox analysis BSI change from baseline to follow-up was significantly associated with OS (p < 0.01 and C-index = 0.6) while age and PSA change were not significantly associated with OS. Conclusions: BSI change during treatment was associated with OS in high-risk PCa patients from the Zeus/SPCG11 study. BSI may be a useful imaging biomarker in future clinical trials involving PCa patients with bone metastases.
Abstracts by Mariana Reza:
Bone scan index as a biomarker to predict outcome in real-life mCRPC patients on abiraterone acetate: A multicenter study.Meeting: 2015 Genitourinary Cancers Symposium | Abstract No: 217
Quantitative imaging by automated bone scan index (BSI) as a response biomarker in standard clinical care of patients with metastatic castration-resistant prostate cancer (mCRPC) treated with enzalutamide.Meeting: 2015 Genitourinary Cancers Symposium | Abstract No: 288