PURPOSE: Circulating tumor cell (CTC) enumeration has not been prospectively validated in standard first-line docetaxel treatment for metastatic castration-resistant prostate cancer.
We assessed the prognostic value of CTCs for overall survival (OS) and disease response in S0421, a phase III trial of docetaxel plus prednisone with or without atrasentan.
PATIENTS AND METHODS: CTCs were enumerated at baseline (day 0) and before cycle two (day 21) using CellSearch. Baseline counts and changes in counts from day 0 to 21 were evaluated for association with OS, prostate-specific antigen (PSA), and RECIST response using Cox regression as well as receiver operator characteristic (ROC) curves, integrated discrimination improvement (IDI) analysis, and regression trees.
RESULTS: Median day-0 CTC count was five cells per 7.5 mL, and CTCs < versus ≥ five per 7.5 mL were significantly associated with baseline PSA, bone pain, liver disease, hemoglobin, alkaline phosphatase, and subsequent PSA and RECIST response. Median OS was 26 months for < five versus 13 months for ≥ five CTCs per 7.5 mL at day 0 (hazard ratio [HR], 2.74 [adjusting for covariates]). ROC curves had higher areas under the curve for day-0 CTCs than for PSA, and IDI analysis showed that adding day-0 CTCs to baseline PSA and other covariates increased predictive accuracy for survival by 8% to 10%. Regression trees yielded new prognostic subgroups, and rising CTC count from day 0 to 21 was associated with shorter OS (HR, 2.55).
CONCLUSION: These data validate the prognostic utility of CTC enumeration in a large docetaxel-based prospective cohort. Baseline CTC counts were prognostic, and rising CTCs at 3 weeks heralded significantly worse OS, potentially serving as an early metric to help redirect and optimize therapy in this clinical setting.
Goldkorn A, Ely B, Quinn DI, Tangen CM, Fink LM, Xu T, Twardowski P, Van Veldhuizen PJ, Agarwal N, Carducci MA, Monk JP 3rd, Datar RH, Garzotto M, Mack PC, Lara P Jr, Higano CS, Hussain M, Thompson IM Jr, Cote RJ, Vogelzang NJ. Are you the author?
University of Southern California Keck School of Medicine and Norris Comprehensive Cancer Center, Los Angeles; City of Hope, Duarte; Philip C. Mack and Primo Lara Jr, University of California, Davis, Sacramento, CA; Southwest Oncology Group Statistical Center; Puget Sound Oncology Consortium, Seattle Cancer Care Alliance, and University of Washington, Seattle, WA; Nevada Cancer Institute; Comprehensive Cancer Centers of Nevada and US Oncology Research, Las Vegas, NV; University of Kansas Cancer Center, Westwood, KS; University of Utah Huntsman Cancer Institute, Salt Lake City, UT; Johns Hopkins Kimmel Cancer Center and Eastern Cooperative Oncology Group, Baltimore, MD; Ohio State University and Cancer and Leukemia Group B, Columbus, OH; University of Miami Miller School of Medicine, Miami, FL; Portland Veterans Affairs Medical Center, Portland, OR; University of Michigan Comprehensive Cancer Center, Ann Arbor, MI; and University of Texas Health Science Center at San Antonio, San Antonio, TX.
Reference: J Clin Oncol. 2014 Apr 10;32(11):1136-42.