MRI Adds Benefits to PSA Screening

A More Accurate Prostate Cancer Diagnosis

Prostate cancer is the most common cancer in men and is the second highest cause of cancer deaths in men, second only to lung cancer. One in every 7 men will be diagnosed with prostate cancer. African-American men face a 1 in 3 chance of being diagnosed with prostate cancer. Over 29,000 men die each year from prostate cancer. Not every man with prostate cancer will die from the disease; some prostate cancers are very slow growing and others are very biologically aggressive.

Prostate-specific antigen (PSA) screening has been widely practiced since the early 1990s. PSA is a substance made by the prostate gland. PSA blood levels are elevated in approximately 80 percent of men with prostate cancer, but an elevation in PSA is not diagnostic of prostate cancer. There are other conditions that can cause the PSA to be elevated, such as prostatitis, urinary tract infections, benign enlargement of the prostate with age, trauma to the prostate, etc. Therefore, the PSA test is not perfect.

The Urology Care Foundation is concerned that recent reports about PSA testing may confuse patients and primary care physicians about the value of this prostate cancer screening tool. There have been recent reports suggesting that PSA screening does not decrease the prostate cancer-specific death rates by a significant amount and that some men may be harmed by “overtreatment” of the slow-growing type that may never have harmed the individual.

As stated above, the PSA test is not perfect. A normal PSA value could mean the individual does not have prostate cancer, and that can be very reassuring. Or it could mean that there is cancer present and the test was a “false negative.” On the other hand, an elevated PSA could mean that a man does have prostate cancer or he may have one of the other conditions as noted above, which would be a “false positive” result.

No More “Blind” Biopsies

The PSA value should be compared with the digital rectal exam (DRE), which could reveal a prostate nodule suspicious for cancer or a very large prostate, which would account for an elevation in the PSA. Until recently the only way to determine if cancer was present was to perform a transrectal ultrasound-guided prostate biopsy. Prostate biopsies only take about 10 minutes and do not cause much pain if a local anesthetic is utilized.

However, prostate biopsies carry certain risks such as infection, hospitalization and bleeding from the biopsy sites. In addition, prostate biopsies are not perfect either, in that they may miss an “aggressive” cancer (present in between the biopsy sites), or reveal a very slow-growing cancer that would never have required treatment during the man’s lifetime.

MRI to the Rescue!

Just within the past year, a new modality has become available to help determine if men with an elevated PSA or an abnormal DRE actually need a biopsy. This new modality is multiparametric MRI. A multiparametric MRI is a 40-minute exam of the prostate. It usually involves an injection of a contrast agent but does not involve x-ray exposure. The radiologist then looks at the images. If an abnormality is identified, the radiologist assigns the area a PIRADS score from 1 to 5. PIRADS stands for Prostate Imaging Recording and Data System.

Low PIRADS-score lesions (1-2) have a very low probability of representing aggressive prostate cancer. Sixty percent of men with elevated PSA who undergo a multiparametric MRI actually have a low PIRADS score and can be spared from an “unnecessary” biopsy. If the radiologist identifies a high PIRADS-score lesion (4-5), there is a 70 percent chance of having a positive biopsy, and usually, these are the aggressive types of prostate cancer that may be life threatening. These patients are likely to benefit from early treatment. A PIRADS 3 lesion is intermediate, with a 10-20 percent chance of having a positive biopsy.

Not only does multiparametric MRI identify men who are at high risk of harboring aggressive prostate cancer, but it also tells us where the cancer lies within the prostate. Software has been developed that allows the MRI image to be transferred to the urologist’s ultrasound screen where the MRI image and ultrasound images can be fused together. This allows the urologist to perform accurate, targeted biopsies of the suspicious lesion, rather than “blind,” systematic biopsies. This is called an MRI-ultrasound fusion-guided biopsy and avoids taking biopsies in areas that are less likely to contain aggressive cancer. This leads to fewer biopsies being performed and a higher percentage of aggressive cancer being detected.

MRI is a valuable tool for men who’ve had previous negative biopsies (sometimes multiple negative biopsies). It is also valuable in men with a rising PSA for which there is no other explanation. Rather than jump to a prostate biopsy, an MRI can help to determine if a biopsy is likely to reveal an aggressive prostate cancer for which early treatment may be lifesaving.

PSA is not a perfect test. Like any screening tool, it has limitations. The choice to use PSA for early detection of prostate cancer is a personal choice. Talk to your primary care physician who knows your complete medical history, knows if you have other life-limiting medical conditions or if you have a long life expectancy and may benefit from prostate cancer screening. Talk with your provider about the benefits and risks of testing. You should talk about factors that can increase your risk for prostate cancer including a family history of prostate cancer (father or brother), African American ethnicity, obesity, etc.

The addition of MRI to help sort out the 60 percent of men who do not need a biopsy from men who are truly at high risk of aggressive prostate cancer is likely to become the standard approach. The use of MRI-ultrasound fusion-guided biopsy greatly increases the accuracy of a biopsy.

Dr. Stephen Taylor is a Urologist with Pacific Urology. He specializes in robotic urologic surgeries and prostate, kidney and bladder cancers. Pacific Urology is the first medical practice to offer the MRI-ultrasound fusion-guided biopsies in the San Francisco East Bay.

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