Circulating tumor cell (CTC) count, measured via liquid biopsy, could be an important prognostic biomarker for metastatic hormone-sensitive prostate cancer (mHSPC), according to a report published in JAMA Network Open.
The researchers evaluated data from the SWOG S1216 clinical trial, involving 1,313 participants, to investigate the association between baseline CTC count and overall survival (OS), progression-free survival (PFS), and prostate-specific antigen (PSA) response.
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CTCs were measured at the start of systemic hormonal therapy for mHSPC, using an FDA-cleared liquid biopsy platform. CTC counts were categorized as 0, 1–4, or 5 or more CTCs per 7.5 mL of blood. Patients with 5 or more CTCs per 7.5 mL had a significantly worse prognosis than those with fewer CTCs – median OS was 27.9 months, compared with 56.2 months for those with 1–4 CTCs; median OS was not reached for patients with 0 CTCs. Similarly, CTC count was associated with PFS, where patients with 5 or more CTCs per 7.5 mL had a median PFS of 11.3 months, compared with 59.9 months for patients with 0 CTCs.
CTC count also correlated with PSA response, with patients exhibiting higher CTC counts being significantly less likely to achieve a complete PSA response. The addition of CTC count to known prognostic factors improved the predictive accuracy for 3-year survival (area under the curve, 0.79).
The report concludes, “This prognostic ability may be of particular benefit in the slate of new clinical trials being launched to test standard mHSPC treatment versus intensified triple therapy (ADT, ARSI, chemotherapy) or other novel combinations. In this new generation of trials, elevated CTC count may serve as a valuable baseline biomarker to enrich the study cohorts for men most likely to benefit from these more aggressive therapeutic strategies.”
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