From the Guidelines
Apalutamide can potentially reduce PSA levels by 50 percent within 14 days in some patients with prostate cancer, though individual responses vary. Apalutamide is an androgen receptor inhibitor approved for treating certain types of prostate cancer, including non-metastatic castration-resistant prostate cancer and metastatic castration-sensitive prostate cancer. The standard dose is 240 mg (four 60 mg tablets) taken orally once daily, alongside ongoing androgen deprivation therapy 1.
Key Points to Consider
- PSA response to apalutamide can be rapid in some patients, with significant declines possible within the first two weeks of treatment.
- This rapid PSA reduction occurs because apalutamide works by blocking androgen receptors in prostate cancer cells, preventing testosterone from stimulating cancer growth and PSA production.
- However, the timing and magnitude of PSA reduction varies between patients based on cancer characteristics, prior treatments, and individual factors.
- Regular PSA monitoring is essential during treatment, typically every 1-3 months initially, but PSA changes alone should not be the sole basis for treatment decisions, especially in the first few months of therapy when PSA flares can occasionally occur before declining 1.
Important Considerations for Treatment
- The SPARTAN trial demonstrated that apalutamide significantly improved metastasis-free survival and overall survival in patients with non-metastatic CRPC, with a 72% reduction in the risk of distant metastasis or death 1.
- Common adverse events associated with apalutamide include fatigue, hypertension, rash, diarrhea, nausea, weight loss, arthralgia, and falls, which should be closely monitored and managed during treatment 1.
From the Research
Apalutamide's Effect on PSA Levels
- The studies 2, 3, 4, 5, 6 investigated the effect of apalutamide on Prostate-Specific Antigen (PSA) levels in patients with prostate cancer.
- According to the study 2, apalutamide plus androgen deprivation therapy (ADT) produced rapid, deep, and durable PSA responses in the majority of patients, with a median time to PSA nadir of 7.4 months.
- The study 4 found that a deep PSA decline (≥90% or to ≤0.2 ng/ml) at landmark 3 months of apalutamide treatment was associated with longer overall survival (OS) and radiographic progression-free survival (rPFS).
- However, none of the studies directly addressed whether apalutamide can reduce PSA levels by 50% within 14 days.
PSA Decline and Clinical Outcomes
- The studies 3, 4, 5, 6 consistently showed that a deep PSA decline in response to apalutamide treatment is associated with improved clinical outcomes, including longer survival time and delayed disease progression.
- The study 6 found that patients with a complete PSA response (PSA ≤0.02 ng/ml) at 3 months had a very low risk of progression within 2 years, while those with an incomplete response had a higher risk of disease progression.
Time to PSA Reduction
- The study 2 reported that the median time to confirmed ≥50% PSA reduction was 1.0 month, and 90% of apalutamide patients had ≥50% PSA reduction by 6 months.
- However, the studies did not provide specific data on the proportion of patients achieving a 50% PSA reduction within 14 days.