Cabazitaxel, a third-generation taxane, was established as third-line therapy for men with metastatic castration-resistant prostate cancer (mCRPC) by the open-label, phase 4 CARD trial. As a correlative study, Dr. Johann S. De Bono and colleagues presented data during the 2021 American Society of Clinical Oncology Genitourinary Cancers Symposium on circulating tumor cells (CTCs) measured in the blood samples of men in the CARD trial at screening and cycle 2 of therapy. They found that high baseline CTC counts were associated with lower survival, while a reduction in CTC counts during therapy was associated with improved progression-free survival.
Of the 255 patients enrolled, a total of 237 (92.9%) men at screening and 213 (83.5%) at cycle 2 had evaluable samples. Over 80% of patients had one or more detectable CTCs at both timepoints (median 4.1 at screening and 5.2 at cycle 2), and the number of CTCs correlated with other serum measurements, including lactate dehydrogenase, alkaline phosphatase, and prostate-specific antigen. Notably, a reduction from a high to low category of CTCs correlated with objective tumor response. The findings suggest CTCs may have some prognostic value for patients with mCRPC both at baseline and by following changes during therapy.
J Clin Oncol 39, 2021 (suppl 6; abstr 161)
de Wit R, de Bono J, Sternberg CN, et al. Cabazitaxel versus Abiraterone or Enzalutamide in Metastatic Prostate Cancer. N Engl J Med. 2019 Dec 26;381(26):2506-2518.