- MRI scans find nearly 90% of all breast cancers, which is a higher rate than the combined detections of ultrasounds and mammograms. This indicates high MRI accuracy.
- MRI scans also outperform CT scans for detecting uterine, prostate, and some liver cancers.
- To determine MRI accuracy, researchers consider sensitivity, specificity, and positive predictive rate.
- A whole-body MRI can be a useful screening tool for early cancer detection.
- MRI scans can help avoid the overdiagnosis and overtreatment of prostate and other cancers.
The accuracy of magnetic resonance imaging (MRI) scans for detecting cancer is high. Because MRI accuracy is typically high, MRI scans are often used when other methods such as CT scans, ultrasound, or X-ray can’t provide enough information to confirm a diagnosis.
An MRI could, in fact, even help you avoid an unnecessary biopsy. For example, a prostate MRI can help doctors tell the difference between harmless and aggressive cancers better than a biopsy.
MRI accuracy is high when detecting breast cancer as well. According to Radiology Today, an MRI scan finds about 90% of all breast cancers. Comparatively, the combined ultrasound and mammography detection rate was just 37.5%.
In this article, we’ll discuss the research and systematic reviews behind MRI accuracy in clinical practice. We’ll then help you weigh the risks and benefits of MRIs, especially as a highly accurate early cancer detection tool.
What Is an MRI?
An MRI is an imaging test that incorporates computer technology to create pictures of your body’s structures, especially soft tissues.
MRI images are often clearer and more detailed than other imaging methods, which makes them a more accurate detection method.
An MRI machine is a large, tube-shaped cylinder. The walls of the tube hold powerful magnets involved in the scan. During the scan, radio waves move your cells’ atomic nuclei out of position. When they move back into place, they send signals for a computer to analyze.
A computer creates the 2D images that your radiologist reads. They’ll report their findings to oncologists, orthopedists, and other medical providers. That information can help your practitioner make a diagnosis and develop your treatment plan.
When used to detect cancer early, an MRI can help you avoid unnecessary or intrusive tests or interventions. Because an MRI machine uses a magnetic field and not ionizing radiation, an MRI is safer than tomography and X-rays.
Health care professionals depend on MRIs for diagnosing cancer, injury, and other abnormalities.
As a radiological modality, MRI findings can also pinpoint the size and location of tumors, lesions, and injuries. A lesion is any damage or abnormal change in the tissue of your body, and it’s usually caused by disease or trauma.
MRI scans outperform CT scans for detecting some cancers such as uterine and prostate cancer and some liver cancers.
An MRI also shows brain and bone metastases (meaning cancer has spread from the initial site) more clearly than a CT scan. That’s because an MRI uses radio waves and a powerful magnet to create the images.
Researchers look at three indicators to determine MRI accuracy: sensitivity, specificity, and the positive predictive value (PPV).
- Sensitivity measures how often a test correctly shows a positive result for those who have cancer — this is known as a “true positive” rate. A test that’s very sensitive will identify almost all cancer and won’t give many false-negative results.
- Specificity gauges a test’s ability to correctly produce a negative result for people who don’t have cancer (a “true negative” rate). A high-specificity test will correctly identify nearly everyone who doesn’t have the disease and won’t generate many false-positive results.
- PPV reflects the proportion of those with a positive result who have cancer.
A combination of these three indicators determines MRI accuracy.
Let’s look at MRI accuracy across different cancers.
Accuracy of MRI Scans in Detecting Breast Cancer
MRI scans may detect more breast cancer than other methods.
In a study of MRI’s role in breast cancer staging, the Journal of Clinical Oncology reported that 66% of the time, MRI could accurately predict cancer incidence.
The increased sensitivity in MRI-assisted cancer staging may lead to more accurate diagnoses, which means more extensive breast surgery. If your MRI indicates additional cancer, talk to your doctor about your treatment options.
The Canadian Medical Association Journal cites two recent studies that show MRIs are more accurate in early breast cancer detection than mammograms.
A study published in the New England Journal of Medicine rated the sensitivity of three methods of invasive breast cancer detection. In the study, the specificity was 98.1%, 95.0%, and 89.8%, respectively, for clinical breast exams, mammograms, and MRIs.
However, keep in mind that the higher percentages for clinical exam and mammography are related to the delay in finding invasive cancer. That’s because the tumors or lesions will be larger and have spread more the later they are discovered.
Often, a clinical exam won’t reveal cancer until the tumor is already relatively large. Similarly, a mammogram sometimes misses “hidden” lesions and small tumors because of dense breast tissue. Dense breast tissue can also return a false-positive in a clinical exam.
However, a 3D mammogram finds more cancers than traditional 2D mammograms, including those hidden by dense breast tissue. 3D mammograms can also allow the radiologist to see up to 300 pictures, as compared to just four from a regular 2D mammogram.
How a Prostate MRI Improves Diagnostic Accuracy
Research indicates MRI scans may be more accurate than other prostate cancer detection methods, especially biopsies.
In one study, tumors were correctly diagnosed in 93% of MRI scans compared to 48% of biopsies. This means a prostate MRI may help avoid unneeded biopsies.
Of the million biopsies performed each year, an estimated 27% are unnecessary.
Avoiding these unnecessary procedures is crucial, as prostate biopsies can cause rectal bleeding, blood in the urine and/or semen, difficulty urinating, and infection. Urinary tract infection is the most common infectious complication of prostate biopsy, occurring in 1 to 11 percent of patients.
Men with elevated PSA levels who want more information about their prostate before undergoing a biopsy can get a prostate MRI with contrast. It will indicate with better accuracy where any potential cancer may be prior to undergoing a biopsy.
A study published by JAMA Oncology showed using a prostate MRI could have meant avoiding 38% of biopsies yet still identifying 89% of clinically significant cancers.
As a biopsy involves random tissue samples, it can miss a cancerous region of the prostate. This means MRI results can also help avoid missed diagnoses.
Orthopedists Use MRIs Because They Are Safe and Precise
Beyond offering more accurate cancer detection, MRIs can also better evaluate orthopedic issues than other diagnostic modalities such as X-rays.
In addition to being safer than an X-ray because there is no radiation, an MRI is more accurate than an X-ray.
A musculoskeletal MRI is important for assessing the results of orthopedic (sometimes orthopaedic) surgery for arthroscopic repairs, such as meniscal tears or anterior cruciate ligament injuries.
Why Should You Have an MRI?
Having an MRI before a biopsy means radiologists can identify exactly where cancer may be. Marking a suspicious area aids a targeted needle biopsy.
Quite possibly, the most significant benefit of MRI is whole-body imaging. The ability to scan head-to-toe means MRIs can detect cancer throughout the body.
A medical provider will often order an MRI scan, but you can also book a scan on your own. Detecting cancer before symptoms occur leads to better treatment plans and a better prognosis.
At ezra, our full body MRI can detect cancer in up to 13 different organs.
What Are the Risks of an MRI?
Because an MRI scan relies on a strong magnetic field and radio waves, it doesn’t expose you to ionizing radiation.
It’s important to tell your doctor or clinician if you have an implant such as a pacemaker, because the MRI machine has a strong magnetic field that could potentially disrupt or move the device.
Some candidates have issues with claustrophobia because of the machine’s close quarters. At some sites, you will be provided with a headset and can select a Spotify playlist to help you relax during the scan.
Radiologists and other health care providers discourage having an MRI during the first trimester.
There’s also the possibility of an adverse reaction to the contrast material. If you have had such a response, discuss it with your doctor, technologist, or radiologist, especially if you also have kidney disease. However, rest assured that ezra does not use contrast material for the full body scan.
MRI Scans Are Often a More Accurate Way To Detect Cancer
MRI scanning is a more accurate tool for detecting some cancers. It may outperform ultrasound, computed tomography (CT), and mammography at identifying more invasive breast cancer. It’s also more accurate than a CT scan for detecting uterine, prostate, and some liver cancers.
Early and accurate detection offers peace of mind. If cancer is detected early, you’ll be that much farther along in your treatment protocol. That’s an easy way to ensure a long, healthy life.
Ezra takes safety to heart and has protocols such as thorough cleanings between exams, social distancing in waiting rooms, and providing MRI-compatible masks to wear during scans. We encourage you to get your annual cancer screening appointments booked.
You can also evaluate your risk of developing cancer with our 5-minute questionnaire.