ASCO20: Predicting Outcomes in Metastatic Prostate Cancer With CTC Counts
Posted: Tuesday, June 2, 2020
The CellSearch circulating tumor cell (CTC) count, a biomarker cleared by the U.S. Food and Drug Administration in metastatic castrate-resistant prostate cancer, may prove to be a useful in predicting outcomes in metastatic castrate-sensitive prostate cancer as well, according to initial results of the prospective phase III SWOG S1216 trial, presented during the ASCO20 Virtual Scientific Program (Abstract 5506). Reliable predictors of clinical outcomes are needed for this patient subgroup, noted lead author Amir Goldkorn, MD, of USC’s Norris Comprehensive Cancer Center, Los Angeles, and colleagues.
“Baseline CTC count may serve as a valuable prognostic marker to discriminate men likely to respond favorably to hormonal therapies from those who may benefit from early alternate interventions,” the researchers commented.
The team gathered baseline CTC samples, 523 in total between 2014 and 2017. Ultimately, CTC count at the start of treatment for metastatic castrate-sensitive prostate cancer was prognostic of two prespecified trial intermediate endpoints: 7-month prostate-specific antigen (PSA) response (intermediate endpoint for overall survival) and progression-free survival at 2 years.
“Adjusting for disease burden (minimal vs. extensive) and ADT status (already initiated or not) at the time of CTC measurement, men with undetectable CTCs [at baseline] were 6.1-fold more likely to attain a 7-month PSA of ≤ 0.2ng/mL (P < .001) and 3.7-fold more likely to achieve a progression-free survival of more than 2 years (P < .001) compared with men with baseline CTCs ≥ 5,” noted Dr. Goldkorn and co-investigators.
Also, they specified, CTCs were detected in 38% of men in the 7-month PSA analysis (n = 264), with a median of 4 CTCs in those with detectable CTCs. In the progression-free survival analysis (n = 336), CTCs were detected in 37% of men, with a median of 3 CTCs in those with detectable CTCs.
Disclosure: The study authors’ disclosure information can be found at coi.asco.org.
