Armstrong AJ, et al. - In a prospectively defined analysis plan of a clinical trial, researchers clinically evaluated the automated Bone Scan Index (aBSI) as an independent prognostic determinant of overall survival (OS) in men with metastatic castration-resistant prostate cancer (mCRPC). The aBSI was shown to be significantly related to overall survival. In a multivariable survival model, aBSI showed an independent association with overall survival. Significant association with additional clinical end points was also demonstrated. Overall, the prognostic utility of the aBSI as an objective imaging biomarker in the design as well as the eligibility of clinical trials of systemic therapies for patients with mCRPC was supported in this largest prospectively analyzed study to validate the aBSI as an independent prognostic imaging biomarker of survival in mCRPC.

Methods

• Researchers undertook this prospectively planned analysis of the aBSI in a phase 3 multicenter randomized, double-blind, placebo-controlled clinical trial of tasquinimod (10TASQ10) including men with bone metastatic chemotherapy-naïve CRPC who were recruited at 241 sites in 37 countries between March 2011 and August 2015.
• Prior to unmasking of the 10TASQ10 study, the statistical analysis plan to clinically assess the aBSI was prospectively defined and locked.
• Between May 25, 2016, and June 3, 2017, the analysis of aBSI was carried out.
• They examined the associations of baseline aBSI with OS, radiographic progression-free survival (rPFS), time to symptomatic progression, and time to opiate use for cancer pain.

Results

• A total of 721 subjects were evaluable for the aBSI, among the total 1245 men enrolled.
• The mean (SD) age (available for 719 men) was noted to be 70.6 (8.0) years (age range, 47-90 years).
• The aBSI population was representative of the total study population based on baseline characteristics.
• The aBSI (median, 1.07; range, 0-32.60) was shown to be significantly related to OS (hazard ratio [HR], 1.20; 95% CI, 1.14-1.26; P < .001).
• By aBSI quartile (lowest to highest), the observed median OS was 34.7, 27.3, 21.7, and 13.3 months, respectively.
• Compared with the manual lesion counting (C index, 0.60) (P=.03), significantly higher discriminative ability was shown by the aBSI (C index, 0.63) in prognosticating OS.
• An independent association of a higher aBSI with OS was shown in a multivariable survival model (HR, 1.06; 95% CI, 1.01-1.11; P=.03).
• A higher aBSI was also found to be independently related to time to symptomatic progression (HR, 1.18; 95% CI, 1.13-1.23; P < .001) and time to opiate use for cancer pain (HR, 1.21; 95% CI, 1.14-1.30; P < .001).