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What is PSA?

Updated

Prostate-Specific Antigen (PSA) is a protein produced by both normal and malignant cells of the prostate gland, commonly measured through a blood test. It is primarily used to screen for prostate cancer, monitor treatment effectiveness, and detect recurrence of the disease. PSA testing is a crucial tool for early detection of prostate cancer. Elevated levels of PSA in the blood can indicate the presence of prostate cancer, although other conditions such as benign prostatic hyperplasia (BPH) and prostatitis can also cause increased PSA levels. Specific PSA thresholds guide clinical decisions. For example, PSA concentrations of ≤ 4.1 μg/L for men under 65 and ≤ 3.7 μg/L for men 65 and older can exclude advanced prostate cancer in patients without glandular inflammation. Conversely, PSA levels > 5.7 μg/L for men under 65 and > 6.1 μg/L for men 65 and older suggest the need for a biopsy.

Various factors can influence PSA levels and the likelihood of undergoing PSA testing. For example, men with a history of ischemic heart disease (IHD) are more likely to have been tested for PSA compared to those without IHD. PSA levels are used to monitor the effectiveness of prostate cancer treatments. A significant decline in PSA levels during treatment with apalutamide and androgen deprivation therapy (ADT) is associated with longer survival and improved outcomes in patients with metastatic castration-sensitive prostate cancer. After treatments like radical prostatectomy or radiation therapy, specific PSA thresholds are used to define biochemical recurrence. A PSA level of ≥ 0.2 ng/mL is commonly used to report biochemical relapse after radical prostatectomy, while a threshold of 2 ng/mL above the post-treatment nadir is used for external beam radiotherapy or brachytherapy. False positive findings can occur in PSA testing, particularly with advanced imaging techniques like PET/CT scans using PSMA-targeting radiopharmaceuticals, which can complicate the interpretation of PSA levels post-treatment.

Further Reading:

  1. Panzone, J., Welch, C., Wu, M. S., Jacob, J. M., Shapiro, O., Basnet, A., Gennady Bratslavsky, & Goldberg, H. (2022). What is the impact of ischemic heart disease on PSA testing? Journal of Clinical Oncology, 40(16_suppl), e17014–e17014. https://doi.org/10.1200/jco.2022.40.16_suppl.e17014
  2. Ferraro, S., Bussetti, M., Bassani, N., Rossi, R. S., Incarbone, G. P., Bianchi, F., Maggioni, M., Runza, L., Ceriotti, F., & Panteghini, M. (2021). Definition of Outcome-Based Prostate-Specific Antigen (PSA) Thresholds for Advanced Prostate Cancer Risk Prediction. Cancers, 13(14), 3381. https://doi.org/10.3390/cancers13143381
  3. Uribe, J., Uribe‐Lewis, S., Khaksar, S., Perna, C., Mikropoulos, C., Otter, S., Laing, R., & Langley, S. (2020). Low‐Dose‐Rate Prostate Brachytherapy (LDR‐PB) adopts postsurgical PSA value for definition of cure. BJUI Compass, 2(1), 9–10. https://doi.org/10.1002/bco2.49
  4. Orevi, M., Ben-Haim, S., Galith Abourbeh, Alexandre Chicheportiche, Eyal Mishani, Vladimir Yutkin, & Gofrit, O. N. (2022). False Positive Findings of [18F]PSMA-1007 PET/CT in Patients After Radical Prostatectomy with Undetectable Serum PSA Levels. Frontiers in Surgery, 9. https://doi.org/10.3389/fsurg.2022.943760
  5. Coelho, M. O., Dal Col, L. S., Capibaribe, D. M., Salgado, C. M., Travassos, T. C., Junior, V. J., Monti, C. R., & Reis, L. O. (2022). PSA nadir predicts biochemical recurrence after external beam radiation therapy combined to high dose rate brachytherapy in the treatment of prostate cancer. American Journal of Clinical and Experimental Urology, 10(1), 52–62. https://pubmed.ncbi.nlm.nih.gov/35291420/
  6. Chowdhury, S., Anders Bjartell, Agarwal, N., Chung, B. H., Given, R. W., Pereira, A. J., Merseburger, A. S., Mustafa Özgüroğlu, Álvaro Juárez Soto, Uemura, H., Ye, D.-W., Brookman-May, S. D., Anil Londhe, Bhaumik, A., Mundle, S. D., Larsen, J. S., McCarthy, S. A., & Chi, K. N. (2024). Prostate-specific antigen (PSA) decline with apalutamide therapy is associated with longer survival and improved outcomes in individuals with metastatic prostate cancer: a plain language summary of the TITAN study. Future Oncology, 20(10), 563–578. https://doi.org/10.2217/fon-2023-0649