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Specialist Advice — 5 minutes

Prostate cancer: The role of PSA and MRI in screening

September 5, 2024

Raymond Lepage, PhD, Doctor in Biochemistry
Raymond Lepage, PhD, Doctor in Biochemistry
Science popularizer

Prostate cancer is the main cancer that affects men and the third leading cause of cancer-related death after lung and colorectal cancer.[1] It is estimated that 1 in 9 Canadian men will develop prostate cancer in their lifetime and that 1 in 29 will die from it.[2] Despite these troubling statistics, the 5-year survival rate for prostate cancer after diagnosis is 91%.[1]

prostate cancer

Screening

For over 25 years, prostate cancer screening has been based on a digital rectal exam (DRE) undertaken in association with a prostate-specific antigen (PSA) blood assay. In recent years, magnetic resonance imaging (MRI) has been increasingly used to confirm PSA test results and determine which patients will benefit from a prostate biopsy and any subsequent treatments.

PSA

PSA is a protein in the blood exclusively derived from the prostate. Depending on age, blood levels below 3 or 4 nanograms per millilitre (ng/mL) are considered safe. Levels between 4 and 10 ng/mL are seen in both cancer and benign prostate disorders, including benign prostatic hyperplasia (BPH) and acute prostatitis. Levels above 10 ng/mL are generally associated with cancer and can be used to estimate disease progression. It is also important to remember that PSA levels are completely normal in almost 15% of prostate cancers.[3]

Men at an intermediate risk of prostate cancer should consider an initial PSA test as of age 50. In the case of men who are at a higher risk (African or Caribbean ancestry, family risk), we are looking at 45 years of age.

Prostate MRI

Magnetic resonance imaging (MRI) of the prostate is a non-invasive exam. It involves creating a strong magnetic field around the prostate and then emitting radio waves to produce very high-precision images of the prostate and the surrounding tissues in 2 or 3 dimensions. MRI is often performed after injection of a contrast agent such as gadolinium.[4]

Diagnosis

A diagnosis of prostate cancer is confirmed by microscopic analysis of the biopsy sample. In fact, many benign prostate disorders such as acute prostatitis and BPH are sometimes difficult to distinguish from cancer. Moreover, not all cancers are equally dangerous; some progress so slowly that that they are unlikely to cause health problems before death from another cause. A biopsy can identify the most dangerous types of cancer, localized infiltration or involvement and, in conjunction with other techniques, the presence of metastases.

PSA testing: The source of overdiagnosis?

PSA testing in asymptomatic men without specific risk factors is known to generate a high number of anxiety-inducing abnormal results that can lead to unnecessary and sometimes dangerous interventions. It is estimated that three-quarters of PSA test results ranging from 4 to 10 ng/mL are not attributable to cancer and are, instead, indicative of a benign prostate disorder that does not warrant a biopsy.[2] A study published in December 2022 in the prestigious New England Journal of Medicine showed that MRI prior to biopsy halved the number of unnecessary biopsies in 17,980 Swedes with PSA levels greater than 3 ng/mL at the expense of a slight reduction in the detection of intermediate-risk cancers.[5]

As with all cancers, the earlier prostate cancer is detected, the greater the chances of survival. Fortunately, we have at our disposal a number of methods, including the combined use of PSA testing and MRI, to detect the cancer early before it progresses. It is important to discuss the advantages and disadvantages of prostate cancer screening with your healthcare professional before an initial PSA test.

We offer services that can help your doctor screen for prostate cancer and determine the appropriate next steps.

Book an appointment online or contact Biron Health Group customer service at 1 888-937-1579 for Imagix services or 1 833-590-2712 for Biron Medical Laboratory services.

Sources5
  1. Government of Canada. Cancer-specific stats 2023. https://cdn.cancer.ca/-/media/files/research/cancer-statistics/2023-statistics/2023_cancer-specific-stats.pdf?rev=52ddcbe77b22436899492c7d152404dc&hash=39800F8EEA2B1B2 Accessed September 5, 2024.
  2. Tétreault N. Demystifying prostate cancer to improve outcomes. https://www.biron.com/en/education-center/specialist-advice/prostate-cancer/ Accessed September 5, 2024.
  3. Canadian Cancer Society. Prostate-specific antigen (PSA) test. https://cancer.ca/en/treatments/tests-and-procedures/prostate-specific-antigen-psa-test Accessed September 5, 2024.
  4. Canadian Cancer Society. Diagnosis of prostate cancer. https://cancer.ca/en/cancer-information/cancer-types/prostate/diagnosis. Accessed September 5, 2024.
  5. Hugosson J, Månsson N, Wallström J, Axcrona U, et al. Prostate cancer screening with PSA and MRI followed by targeted biopsy only. NEJM 2022; 387: 2126-2137.7.