MRI May Reduce Unnecessary Prostate Biopsies

Despite its false negatives, a transrectal prostate biopsy is one of the best ways to detect prostate cancer. However, it is related to severe side effects, and some of them turn into long-term consequences. That’s why the topic of unnecessary prostate biopsies is frequently brought up in the medical community.

Urologists are trying to find new techniques and alternatives to offer excellent medical care and low risks at the same time. One of them is an MRI-targeted biopsy, which does not involve as many biopsy cores. But it is not for everyone. Consequently, scientific studies are designed to evaluate several exams’ sensitivity and specificity to detect prostate cancer. A more sensitive and specific exam might reduce the need for a prostate biopsy.

The number of studies about unnecessary biopsies is tremendous, but only a few are medically relevant. One of those medically relevant articles published in the May 2018 issue of the journal JAMA Oncology. In this article, we’re reviewing the most critical aspects of this study, and how is it guiding medical decisions.

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The study

This study was first published online in February 2018 and finally published in a paper in May. It was led by Sherif Mehralivand, an M.D. from the National Cancer Institute, and his research team. They used magnetic resonance imaging (MRI) as a screening tool to detect prostate cancer. After obtaining patients with positive findings in their MRI, they looked for ways to identify patients who need a biopsy.

In other words, their question was: In patients with positive findings in MRI, is there a way to know if they really need a prostate biopsy? So, their research was not only about detecting high-suspicion images. It was about achieving the most accurate differentiation of prostate cancer cases using this tool. They used a technique known as multiparametric MRI (multiparametric magnetic resonance imaging).

Methodology

They included 651 patients who were screened for prostate cancer. Each one underwent digital rectal exams and a PSA test. But they also had an MRI scan, a Transrectal Ultrasound Biopsy (TRUS biopsy) with MRI, and a systematic biopsy of 12 cores. Out of these patients, 289 had prostate cancer. According to their data, using MRI only had the potential to avoid 18% of biopsies. As it does, it would still identify 89% of significant prostate cancer cases.

They performed their study in two stages. In stage 1, they took data from 400 patients in a development cohort. After evaluating their biopsies and MRI findings, the researchers designed a prediction model. This model contemplated the patient’s ethnicity, age, the MRI lesion category, and some clinical variables. In stage 2, they tested this prediction model using data from 251 patients in a validation cohort. These patients had the same studies, and their results were compared to the prediction model.

Results

The researchers wanted to know if this model could accurately predict who needed a prostate biopsy. It turns out that 38.2% of the patients in the validation cohort were diagnosed with prostate cancer, and the model with a multiparametric MRI could predict cancer in most.

There’s something in statistics called Area Under the Curve or AUC. When this measure reaches 1, the prediction is 100% accurate. Of course, we can’t expect a 100% precise study in medicine because only a few would reach that number. But we want prediction models to be as close to 100% as possible. This particular model designed by Dr. Sherif Mehralivand and collaborators increased the curve’s baseline area from 64% to 84%.

In other words, we would be able to predict 64% of cases without MRI parameters. But using this technology increases the rate of prediction to 84%. False-positive cases would also reduce from 92 to 46%.

Conclusions and highlights

The authors concluded that including multiparametric MRI scans with specific parameters in the risk model increases screening accuracy. This technique could reduce unnecessary biopsies’ worldwide burden and their side effects in patients with suspected prostate cancer who do not really have a malignancy.

It is essential to highlight that MRI scans and the prediction model developed by Dr. Sherif Mehralivand were designed for prostate cancer detection at a Gleason score of 7 or more. This is clinically significant prostate cancer as opposed to the very early stages of the disease. However, most cases of prostate cancer have very slow growth and an extended survival rate. Thus, it would be counterintuitive to detect prostate cancer at an early stage in senior patients who are more likely to pass from unrelated causes. That is why Gleason score of 7 and higher was chosen in this study as the definition of clinically significant prostate cancer.

Pros/ Cons MRI

Health sciences are in constant update, but they are far from being perfect. Thus, doctors need to evaluate the pros and cons of MRI and any other diagnostic tool before using them.

Here’s a brief summary of the pros and cons that your doctor will probably consider before recommending a prostate MRI vs biopsy to screen for prostate cancer:

Pros

  • It reduces the need for prostate biopsies. One of the most significant findings of the study is that fewer patients need prostate biopsies if the prediction model was adopted. Prostate biopsies are uncomfortable, and some patients experience side effects. Thus, sparing this process for patients who won’t really benefit is always good news.

  • It prevents overdiagnosis of low-grade cancer. Detecting cancer from an early course is usually a good thing. Prostate cancer is different, though. Prostate cancer usually grows for many years before causing symptoms. It takes even more time to cause problems and become lethal. Thus, it wouldn’t make sense to diagnose an 85-year-old man with low-grade prostate cancer. MRI screening could reduce this rate, sparing them the anxiety of a diagnosis that is unlikely to affect them.

  • It is easy and non-invasive. It is easier to perform an MRI than a prostate biopsy. And it doesn’t require any special care after the procedure, either. It is non-invasive and not as uncomfortable as a prostate biopsy procedure.

Cons

  • It won’t be helpful in early-onset prostate cancer. Early-onset prostate cancer is a type of aggressive prostate cancer in young males. Genetic factors are usually involved, speeding up the growth and spread of cancer. This type of cancer needs to be diagnosed as soon as possible, especially in patients with a family history of early-onset prostate cancer. In this case, we need to detect low-grade prostate cancer as well. As such, MRI techniques should be a part of the arsenal, but not the only one.

  • True positive rate is somewhat lower. In the study reviewed above, the true-positive rate suffered a slight reduction. The baseline model had a 99% true-positive rate. The prediction model had an 89%. This means that MRI scans missed 10% of cases. Thus, it is essential to evaluate the risks and act accordingly, sometimes using several screening tools and not only one.

Pros/Cons Biopsy

Similar to an MRI scan, biopsies also have positive and negative aspects. Doctors will consider your options based on your risk and other parameters. Here’s a list of the pros and cons of a prostate biopsy:

Pros

  • The most reliable diagnostic tool. Biopsies are the most reliable tool to diagnose prostate cancer. A false negative biopsy is likely from cancer in the anterior prostate, a very uncommon location.

  • It is essential to complete the diagnosis. A biopsy is the last stage of a prostate cancer diagnosis. It is vital to have a complete understanding of prostate cancer and confirm your case.

  • It provides an insight into the prognosis and guides the treatment. After a prostate biopsy, you will get a Gleason score. This provides helpful information about what is happening in the tumor and what to expect. Based on these findings, your doctor may decide on a radical prostatectomy or another treatment.

Cons

  • It is invasive and uncomfortable: The experience of a prostate biopsy is very uncomfortable. Some patients mention that they won’t accept a repeat biopsy, even if it’s mandatory.

  • Many patients experience side effects: Short-term and long-term side effects include pain, infection, bleeding, and temporary worsening of the urinary symptoms.

Conclusion

Comparing a prostate MRI vs. biopsy to screen for prostate cancer, each one has its own applications. However, a recent study showed that MRI scans could reduce the need for TRUS-guided biopsy of the prostate gland. In this study, patients had an MRI fusion biopsy, and other clinical findings were considered to develop a predictive model.

Applying the same model in another group of patients, the researchers could predict which patients needed a biopsy. This technique could spare a vast number of biopsies from patients who won’t benefit from them. It will also reduce the overdiagnosis of prostate cancer in patients with early-onset disease.

Next Up

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Find out Alternatives To A Prostate Biopsy.

Sources

  1. Mehralivand, S., Shih, J. H., Rais-Bahrami, S., Oto, A., Bednarova, S., Nix, J. W., … & Turkbey, B. (2018). A magnetic resonance imaging–based prediction model for prostate biopsy risk stratification. JAMA oncology4(5), 678-685.
Alternative Text

Dr Alberto Parra

Dr. Alberto Parra is a Medical Doctor and clinical researcher with extensive experience in diagnostic imaging and sports medicine. He's also interested in nutrition, fitness and family medicine, with expertise and continuing education on preventive healthcare and evidence-based medicine. He provides consultancy services to a number of individuals and entities who require medical validation of their protocols, products, supplements, and medical contents.

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