From the Guidelines
A low PSA level in a patient with known metastatic prostate cancer is associated with improved survival, particularly if the PSA value is ≤4 ng/mL after 7 months of androgen deprivation therapy (ADT) 1. This association is crucial for managing patients with metastatic disease at presentation. The primary treatment for such patients is ADT, which can be administered through various options, including orchiectomy, LHRH agonist, LHRH antagonist, or a combination of these with docetaxel or abiraterone 1. When considering the implications of a low PSA in this context, it's essential to differentiate between a favorable response to treatment and potential progression to a more aggressive form of the disease. Key considerations include:
- The timing and magnitude of PSA reduction in response to ADT
- The presence of symptoms or signs suggestive of disease progression
- The results of comprehensive imaging studies, such as CT, bone scan, and possibly PSMA PET
- Laboratory tests, including chromogranin A, neuron-specific enolase, and a complete metabolic panel, to assess for neuroendocrine features or dedifferentiation In patients with asymptomatic, castration-naïve, metastatic prostate cancer, intermittent ADT may be considered if PSA falls below certain thresholds, such as <4 ng/mL, with the awareness of a possible small trade-off in overall survival for improved quality of life during the off cycle 1. However, the decision to adjust treatment should be based on the most recent and highest quality evidence, prioritizing the patient's morbidity, mortality, and quality of life. Given the complexity of managing metastatic prostate cancer, a multidisciplinary approach, including urology, medical oncology, and radiation oncology, is recommended to tailor treatment to the individual patient's needs and disease characteristics.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Implications of a Low PSA in Metastatic Prostate Cancer
- A low PSA level in patients with metastatic prostate cancer may not necessarily be associated with better overall survival, as seen in a study where no significant differences in OS were observed among patients with different PSA levels 2.
- However, patients with high PSA levels had significantly shorter PSA progression-free survival (PFS) for first-line androgen deprivation therapy (ADT) 2.
- In contrast, patients with high PSA levels had significantly longer PFS when treated with antiandrogen withdrawal (AW) and alternative antiandrogen (AA) therapies after developing castration-resistant prostate cancer (CRPC) 2.
- The magnitude of PSA decline after treatment with enzalutamide was strongly associated with better clinical and patient-reported outcomes in men with metastatic castration-resistant prostate cancer 3.
- A study suggested that intense androgen-deprivation therapy with abiraterone acetate plus leuprolide acetate may result in improved clinical outcomes in patients with localized high-risk prostate cancer by suppressing tissue androgens more effectively 4.
- Patients with very low PSA levels (< 10 ng/mL) at death had lower rates of imaging within 6 months of death, lower treatment rates, and worse clinical outcomes, suggesting that imaging may be underutilized in this patient population 5.
Clinical Considerations
- The prognostic significance of initial PSA level for metastatic prostate cancer remains uncertain, and more research is needed to understand the implications of a low PSA level in this patient population.
- PSA decline after treatment is a valuable prognostic marker, and greater degrees of PSA decline are associated with longer overall survival and better clinical outcomes 3.
- The use of imaging in patients with very low PSA levels may be underutilized, and clinicians should consider routine imaging in this patient population to improve clinical outcomes 5.