Abstract
.A clinical validation of the bone scan lesion area (BSLA) as a quantitative imaging biomarker was performed in metastatic castration-resistant prostate cancer (mCRPC). BSLA was computed from whole-body bone scintigraphy at baseline and week 12 posttreatment in a cohort of 198 mCRPC subjects (127 treated and 71 placebo) from a clinical trial involving a different drug from the initial biomarker development. BSLA computation involved automated image normalization, lesion segmentation, and summation of the total area of segmented lesions on bone scan AP and PA views as a measure of tumor burden. As a predictive biomarker, treated subjects with baseline BSLA had longer survival than those with higher BSLA ( and ). As a surrogate outcome biomarker, subjects were categorized as progressive disease (PD) if the BSLA increased by a prespecified 30% or more from baseline to week 12 and non-PD otherwise. Overall survival rates between PD and non-PD groups were statistically different ( and ). Subjects without PD at week 12 had longer survival than subjects with PD: median 398 days versus 280 days. BSLA has now been demonstrated to be an early surrogate outcome for overall survival in different prostate cancer drug treatments.
Highlights
New drugs are under development for metastatic castration-resistant prostate cancer, and there is a need for biomarkers to identify target populations and for early evaluation of treatment effects as an alternative to overall survival, which leads to long studies and is becoming problematic due to subject crossover and contamination from multiple therapies
The Prostate Cancer Working Group 2 (PCWG2) developed visually based criteria for assessing disease progression on bone scans based on counting new lesions.[8]
A prespecified 30% increase in bone scan lesion area (BSLA) from baseline to week 12 was used to identify subjects with progressive disease (PD)
Summary
Whole-body bone scintigraphy is the accepted standard imaging modality for detection of bone metastases and assessment of treatment outcomes. Response evaluation criteria in solid tumors, the standard guideline used to assess outcomes in solid tumor malignancies, treats bone lesions as “nonmeasurable” and is of limited usefulness in the setting of prostate cancer treatments.[7] the Prostate Cancer Working Group 2 (PCWG2) developed visually based criteria for assessing disease progression on bone scans based on counting new lesions.[8] PCWG2 does address the significance of changes in intensity, size, or area of individual lesions, all of which are limited by the challenges of subjective, visual lesion detection
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