"The study confirmed that the onset and depth of PSA reductions observed after initiating treatment with apalutamide are indeed associated with the outcomes most important to us clinically, including metastasis-free survival and overall survival," said Dr. Jeffrey J. Tosoian, an assistant professor in the division of urologic oncology at Vanderbilt University Medical Center in Nashville, Tennessee.
"PSA levels early in the course treatment with apalutamide can provide important information regarding longer-term outcomes, further supporting the use of PSA testing to monitor treatment response," Dr. Tosoian, who was not involved in the study, told Reuters Health by email.
As reported in European Urology, Dr. Fred Saad of the University of Montreal in Quebec, Canada, and colleagues analyzed data from the placebo-controlled SPARTAN trial. They compared 806 patients with nmCRPC who received apalutamide plus ADT with 401 demographically and clinically matched patients who received placebo plus ADT.
While PSA increased in most placebo-treated patients, at six months, those treated with 240 mg per day of apalutamide showed rapid, deep reduction in PSA, including a 50% or greater PSA drop in 90% of treated patients at a median of 1.0 month and a 90% PSA drop in 57% of treated patients at a median of 1.9 months.
The median time to PSA nadir was 7.4 months from the start of apalutamide treatment, and PSA reductions were similar across molecular subtypes.
A 90% or greater drop in PSA was strongly and inversely associated with the risk of metastasis (hazard ratio, 0.41; P<0.001) or death (HR, 0.45; P<0.001).
Dr. Bilal A. Siddiqui, an assistant professor of genitourinary medical oncology at The University of Texas MD Anderson Cancer Center in Houston, said, "The strength of this study is its reporting of PSA kinetics and responses in molecular subtypes from a large, randomized phase III trial."
He noted, though, that the study's post hoc design is a weakness that makes the findings inconclusive.
"Not every patient had available tissue for molecular analysis; the role of the molecular subtypes in this disease state was not well defined," added Dr. Siddiqui, who was not involved in the study. "Also, nmCRPC is defined based on conventional scans, and this disease state will change with the growing adoption of PSMA PET (prostate-specific membrane antigen positron-emission tomography) scans for more sensitive disease detection."
"For the practicing clinician, apalutamide, enzalutamide, and darolutamide have similar efficacy and acceptable safety," he explained. "Therefore, the approach for selecting a drug is based on careful consideration of individual safety profiles, drug-drug interactions, and cost considerations."
Dr. Shiuan Chen, professor and chair of the department of cancer biology at City of Hope Comprehensive Cancer Center in Duarte, California, said, "Patients have the choice of different androgen-receptor antagonists for their treatment."
"It is important to compare the results generated from apalutamide with those of the two other drugs," Dr. Chen, who also was not involved in the study, told Reuters Health by email. "Patients and clinicians should pay attention to the side effects associated with the use of apalutamide."
Janssen Research & Development sponsored the study and was involved in all aspects of it, including manuscript preparation. The authors report financial ties to the company, which makes apalutamide.
Dr. Saad did not respond to requests for comment.
SOURCE: https://bit.ly/3sqXBDj European Urology, online December 13, 2021.
By Lorraine L. Janeczko
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