Prostate-specific Antigen & Prostate Cancer
Prostate cancer is the most common form of cancer in men. In the UK, 1 in every 8 men will be diagnosed with the condition within their lifetime, resulting in around 12’000 deaths per year1. Prostate-specific antigen is a major protease found in semen which functions to cleave semeogelins into smaller polypeptides resulting in the liquefication of semen2.
This week, we had the pleasure of welcoming Dr Floris Helmich, who discussed laboratory imprecision relating to Prostate-specific antigen (PSA) and prostate cancer in our latest webinar. Dr Helmich took the time out of his busy schedule to present his experience in PSA quantification and the importance of quality control in yielding accurate and precise results as well as discussing some of the experimental techniques he has found useful in identifying the source of bias laboratory testing. Dr Helmich also discussed the ambiguity relating to reporting ranges and how bias can affect the results of laboratory PSA testing.
What is PSA?
PSA is an enzyme produced by the prostate ductal and acinar epithelium where it is secreted into the lumen before it is used to liquefy semen. Once PSA enters circulation, most are bound to protease inhibitors, however, some remain inactive and circulate in the lumen as free PSA2.
PSA levels in men vary depending on their age. Typically, men between the ages of 50 and 69 should have a PSA level below 3ng/ml. If the PSA concentration exceeds 3ng/ml, it could be a potential indicator of prostate cancer3. However, the challenge with using PSA as the sole monitoring method for prostate cancer is the relatively high false positive rate associated with it. A higher PSA concentration can also be attributed to conditions such as an enlarged prostate, prostatitis, or a urinary tract infection4.
Research indicates that 1 out of 4 men with elevated PSA levels will actually have prostate cancer. Additionally, it has been observed that approximately one in every seven men diagnosed with prostate cancer will maintain normal PSA levels3. These findings highlight the limitations of relying solely on PSA screening for prostate cancer diagnosis. As a result, some countries have started to limit their recommendations regarding PSA-based prostate cancer diagnosis.
In response to these limitations, other countries have chosen to maintain their recommendations for PSA testing but are augmenting the guidelines by incorporating additional criteria to ensure more accurate diagnoses.
Elevated levels of PSA should not always be automatically interpreted as a sign of prostate cancer. In older men, one common cause of elevated PSA is benign prostatic hyperplasia (enlarged prostate). Additionally, prostatitis, which refers to inflammation of the prostate, can contribute to an increase in PSA concentration3. It’s important to consider other potential factors that can lead to elevated PSA levels, such as urinary tract infections, recent sexual activity, natural age-related increases, or injury to the groin area5.
Therefore, when assessing PSA levels, it is crucial to recognize that various non-cancerous conditions can also result in elevated PSA. It is recommended to consult healthcare professionals who can evaluate the individual’s medical history, perform further diagnostic tests, and consider other clinical factors to accurately determine the underlying cause of elevated PSA and make informed decisions about the next steps in diagnosis and treatment.
Ultra-low PSA concentrations
The diagnostic accuracy of PSA concentration for prostate cancer is known to be limited. However, there is a clear association between PSA levels and prostate cancer, which confirms it as a valuable tool for risk stratification and diagnosis when used in conjunction with other established factors.
PSA testing also plays a crucial role in monitoring patients who have undergone treatment for prostate cancer. In cases where the patient is deemed cancer-free, their PSA levels should decrease to within the normal range. Following radical prostatectomy (removal of the entire prostate), PSA levels should ideally be undetectable. Post-radiotherapy, it is expected that PSA levels will reach their lowest point (nadir) within 12-18 months. However, it’s important to note that in some cases, a temporary spike in PSA concentration has been observed after radiotherapy. This spike should not be immediately interpreted as recurrent cancer, but these patients should be closely monitored.
If PSA concentrations rise above 2.0ng/ml after radiotherapy, further testing is recommended to assess the possibility of recurrent cancer. Close monitoring and additional evaluations will help healthcare professionals make accurate and timely decisions regarding the patient’s ongoing treatment and care6
Different countries offer varying guidance in relation to Ultra-low PSA testing. The table below details some of these recommended guidelines:
|American Urology Association 7||PSA concentrations of >0.2ng/ml, followed by a subsequent confirmatory >0.2ng/ml result should be considered biochemical recurrence. However, a cut-off of 0.4ng/ml may better predict metastatic relapse.|
|European Association of Urology8||A detectable PSA indicating relapse should be differentiated from a clinically meaningful relapse. PSA thresholds that predict further metastasises are:
Post-RP = >0.4ng/ml
Post-RT = nadir + 2ng/ml
|Prostate Cancer Foundation1||Post-RP = PSA 0.2ng/ml is indicative of biochemical recurrence
Post-RT = PSA nadir + 2ng/ml is indicative of biochemical recurrence
Randox Ultra-low PSA Control
We are excited to introduce Randox’s latest innovation, the Ultra-low PSA Control, designed to assist in the precise quantification and monitoring of ultra-low levels of PSA in post-therapy prostate cancer patients. This control has been specifically optimized for use on Roche systems, ensuring exceptional performance and compatibility. Moreover, it is versatile enough to be utilized on various other platforms, making it the sole control available on the market for measuring ultra-low levels of PSA across a range of instruments.
With the Acusera Ultra-low PSA Control, healthcare professionals can achieve accurate and reliable results, enabling them to monitor the progress and treatment response of prostate cancer patients with heightened sensitivity. With a clinically relevant concentration of approximately 0.055ng/ml, this advancement in control technology contributes to enhanced patient care and supports medical professionals in making informed decisions regarding treatment adjustments or further interventions.
Randox’s commitment to innovation and precision in diagnostic solutions continues with the Ultra-low PSA Control, empowering laboratories to deliver high-quality and dependable PSA measurements, even at the ultra-low levels required for post-therapy monitoring.
Take a look at our webinar, Laboratory Imprecision in Relation to PSA and Prostate Cancer Follow-up, with Dr Floris Helmich to learn about how his clinical laboratory deals with bias at quality control relating to Ultra-low PSA quantification
If you’d like to learn more about PSA testing and prostate cancer, we encourage you to read our new educational guide, Ultra-low PSA and Prostate Cancer
If you would like an additional information on our Ultra-low PSA Control, or anything else relating to Quality Control, don’t hesitate to reach out the firstname.lastname@example.org. Additionally, feel free to visit our QC resource hub where you will find all of our brochures, support tools and a collection of educational material, to aid you in maintaining the highest possible levels of quality.
- Prostate Cancer Foundation. About prostate cancer. Prostate Cancer UK. Published 2023. https://prostatecanceruk.org/prostate-information-and-support/risk-and-symptoms/about-prostate-cancer
- Balk SP, Ko YJ, Bubley GJ. Biology of Prostate-Specific Antigen. Journal of Clinical Oncology. 2003;21(2):383-391. doi:https://doi.org/10.1200/jco.2003.02.083
- NHS Choices. Should I have a PSA test? – Prostate cancer. NHS. Published 2019. https://www.nhs.uk/conditions/prostate-cancer/should-i-have-psa-test/
- Isono T, Tanaka T, Kageyama S, Yoshiki T. Structural Diversity of Cancer-related and Non-Cancer-related Prostate-specific Antigen. Clinical Chemistry. 2002;48(12):2187-2194. doi:https://doi.org/10.1093/clinchem/48.12.2187
- Mejak SL, Bayliss J, Hanks SD. Long Distance Bicycle Riding Causes Prostate-Specific Antigen to Increase in Men Aged 50 Years and Over. Steyerberg EW, ed. PLoS ONE. 2013;8(2):e56030. doi:https://doi.org/10.1371/journal.pone.0056030
- Santis D, Gillessen S, Grummet J, et al. EAU-EANM-ESTRO-ESUR-ISUP-SIOG Guidelines on Prostate Cancer.; 2023.
- AUA. Advanced Prostate Cancer: AUA/ASTRO/SUO Guideline (2020) – American Urological Association. www.auanet.org. Published 2023. https://www.auanet.org/guidelines-and-quality/guidelines/advanced-prostate-cancer
- Sindhwani P, Wilson CM. Prostatitis and serum prostate-specific antigen. Current Urology Reports. 2005;6(4):307-312. doi:https://doi.org/10.1007/s11934-005-0029-y