This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
In a study involving 400 men aged 50 – 69, magnetic resonance imaging (MRI) screening:
- identified more men with prostate cancer than blood tests for prostate-specific antigen (PSA) or ultrasound
- did not increase the number of men who needed a biopsy.
A large-scale trial, TRANSFORM, is due to start in the UK soon. It will investigate the most promising screening approaches for prostate cancer.
More information on prostate cancer is available on the NHS website.
The issue: could MRI be used to screen for prostate cancer?
In the UK, more than 52,000 men are diagnosed with prostate cancer each year. Men over 50 years are at increased risk, as are black men over 45 years, and those with a family history of the disease. The UK does not have a routine screening programme, but men who are concerned can speak to their GP about whether a blood test for PSA is right for them.
A screening programme for prostate cancer would need to detect serious cancers, while not picking up slow-growing, low-risk prostate cancers, which are unlikely ever to cause harm in a man’s lifetime. The existing PSA blood test alone is not accurate enough to use as a routine screening test. A positive result (3ng/mL or above) may suggest cancer when the risk is low, leading to worry, invasive tests (biopsies) and unnecessary treatment. A negative result may miss serious cancers, leading to false reassurance.
MRI and ultrasound tests can also detect prostate cancer and could give more reliable results. This study therefore compared the benefits and risks of MRI, ultrasound and blood tests for prostate cancer screening.
What’s new?
The study included 408 men aged 50 – 69 from 7 GP clinics. A high proportion (132) of participants were black. Between 2018 – 2019, they all had an MRI, ultrasound, and blood test. If any test suggested cancer, a biopsy was recommended.
For the MRI and ultrasound tests, clinicians rated their suspicion of cancer from 1 (least likely) – 5 (most likely). Using a cut-off of 4 – 5, there were similar numbers of positive tests for MRI (43) and ultrasound (52), compared with blood tests (40).
Using a cut-off score of 4 – 5, MRI tests:
- detected a higher number of serious prostate cancers (11) than ultrasound (4) or blood tests (7)
- detected similar numbers of low-risk cancers that are unlikely ever to cause harm (5), compared with ultrasound (7) and blood tests (6)
- led to fewer biopsies that are not cancer (22) than ultrasound (35), but a similar number to blood tests (23).
The numbers in this study were too small for researchers to establish whether differences in cancer detection between the groups were meaningful; larger trials are needed before these findings could be put into routine practice.
A separate analysis found that combining MRI and blood tests (MRI score of 4 – 5 and PSA more than 1 ng/mL) maintained the detection of serious cancers while minimising unnecessary biopsies.
In a related study, the researchers asked the same group of men what they thought of the screening methods. After the tests, many men preferred MRI (40%) to ultrasound (2%) and blood tests (19%); others had no preference (38%). Overall, few men reported high levels of anxiety, burden, pain or embarrassment following any test; though ultrasound prompted more of these responses than MRI or blood tests.
Why is this important?
Combining MRI and blood test results struck a balance between finding serious cancers and avoiding unnecessary biopsies (for low-risk cancers). Ultrasound offered no benefit over blood tests or MRI. The researchers suggest MRI tests could be used in a future prostate screening programme, though more research is needed.
Black men are at increased risk of prostate cancer but have been under-represented in previous screening trials. This study successfully recruited a high proportion of black men.
Any future screening programme would need to address several barriers. First, the trial used a non-contrast (short) MRI scan, which was acceptable to all men and faster than other types of MRI, making it more attractive as a screening tool. However, it costs more and is less readily available than ultrasound or blood tests.
Second, when different doctors assessed the MRI tests, there was some disagreement in the scores. Therefore, more consistent interpretation of the MRIs would be needed for the test to be reliable. In addition, this study used a biopsy result, rather than deaths from prostate cancer, to assess whether cancers were serious. Long-term follow up would be needed to confirm whether MRI screening can reduce deaths from prostate cancer.
What’s next?
A large trial of promising screening approaches for prostate cancer, TRANSFORM, is due to start this year, and will involve hundreds of thousands of participants. The researchers aim for at least 1 in 10 participants to be black. The project will also assess the value for money of prostate cancer screening.
You may be interested to read
Eldred-Evans D, and others. Population-Based Prostate Cancer Screening With Magnetic Resonance Imaging or Ultrasonography. JAMA Oncology 2021; 7: 395 – 402.
A YouTube video about the study.
A summary of the study by Imperial College London.
Prostate Cancer UK has a 30 second risk checker and more information.
Information on taking part in NIHR research on prostate cancer.
Funding: This study was supported by the NIHR Imperial Biomedical Research Centre.
Conflicts of Interest: Several of the study authors have received funding from pharmaceutical companies. See paper for full details.
Disclaimer: Summaries on NIHR Evidence are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that the views expressed are those of the author(s) and reviewer(s) at the time of publication. They do not necessarily reflect the views of the NHS, the NIHR or the Department of Health and Social Care.
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