Baseline circulating tumor cell count as a prognostic marker of PSA response and disease progression in metastatic castrate sensitive prostate cancer (SWOG S1216).

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 CTC count, an FDA-cleared assay in metastatic castrate resistant PC (mCRPC), is a relevant biomarker in mCSPC.