Publication
Baseline Circulating Tumor Cell Count as a Prognostic Marker of PSA Response and Disease Progression in Metastatic Castrate-Sensitive Prostate Cancer (SWOG S1216)
Publisher:
American Association for Cancer Research (AACR)
Date:
26-01-2021
DOI:
10.1158/1078-0432.CCR-20-3587
Abstract: In metastatic castrate-sensitive prostate cancer (mCSPC), combined androgen axis inhibition is a standard of care. Noninvasive biomarkers that guide initial therapy decisions are needed. We hypothesized that CellSearch circulating tumor cell (CTC) count, an FDA-cleared assay in metastatic castrate-resistant prostate cancer (mCRPC), is a relevant biomarker in mCSPC. SWOG S1216 is a phase III prospective randomized trial of androgen deprivation therapy (ADT) combined with orteronel or bicalutamide for mCSPC. CellSearch CTC count was measured at registration (baseline). Prespecified CTC cut-off points of 0, 1–4, and ≥5 were correlated with baseline patient characteristics and, in a stratified subs le, were also correlated with two prespecified trial secondary endpoints: 7-month PSA ≤0.2 ng/mL versus 0.2–4.0 versus & .0 (intermediate endpoint for overall survival) and progression-free survival (PFS) ≤ versus & years. A total of 523 patients submitted baseline s les, and CTCs were detected (median 3) in 33%. Adjusting for two trial stratification factors (disease burden and timing of ADT initiation), men with undetectable CTCs had nearly nine times the odds of attaining 7-month PSA ≤ 0.2 versus & 4.0 [OR 8.8, 95% confidence interval (CI), 2.7–28.6, P & 0.001, N = 264] and four times the odds of achieving & 2 years PFS (OR 4.0, 95% CI, 1.9–8.5, P & 0.001, N = 336) compared with men with baseline CTCs ≥5. Baseline CTC count in mCSPC is highly prognostic of 7-month PSA and 2-year PFS after adjusting for disease burden and discriminates men who are likely to experience poor survival outcomes.
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