Prostate cancer can vary widely in severity and its potential to spread. This simple fact often makes fundamental decisions concerning whether to treat prostate cancer or to monitor it with active surveillance difficult. This difficulty also means that newly diagnosed prostate cancer is too often either under treated or over treated.
Being able to diagnosis accurately and grade prostate cancer would help avoid both overtreatment and under treatment. Low-grade prostate cancer is associated with a very low risk of cancer-specific death and often doesn’t require treatment. High-grade tumors are much more likely to spread and are responsible for most prostate cancer deaths; thus they should be treated.
Currently, systematic biopsies or blind biopsies are often used to diagnose and make treatment decisions for prostate cancer. A systemic biopsy is a nontargeted method of taking blindly spaced samples across the prostate gland to find cancer. Systemic biopsies do not use any form of visualization when the biopsies needles are inserted into the prostate gland; often, these needles will miss areas of cancer. Given the blind nature of these biopsies, sometimes doctors will recommend over treatment of low-grade disease, fearing there is high-grade disease present that was missed. Or, if an aggressive cancer is missed, a patient may be undertreated.
The better alternative to systemic biopsies is MRI-targeted biopsies, which combine MRI images with real-time ultrasound technology to target suspicious areas for biopsy. MRI-targeted biopsies are better able to detect more high-grade cancers than systematic biopsies, insuring that dangerous cancers do not go untreated.
A team led by Dr. Peter A. Pinto at NIH’s National Cancer Institute (NCI) carried out a study to confirm that it is better to replace systematic biopsy with MRI-targeted biopsies or if it is even better to use both tests together. They compared these two methods on more than 2,100 men who had MRI-visible lesion. Their study results were published on March 5, 2020, in the New England Journal of Medicine.
They found that:
Adding MRI-targeted biopsies to the traditional prostate biopsy created a more accurate diagnosis and prediction of the course of prostate cancer, allowing better treatment decisions.
The data:
Participants underwent both MRI-targeted and systematic biopsies. More than 1,300 men were diagnosed with cancer, and 404 men had a prostatectomy, the surgical removal of their prostate glands.
By comparing diagnoses from systematic biopsy alone to systematic biopsy plus MRI-targeted biopsy, the researchers found that combining the methods led to 208 more cancer diagnoses than systematic biopsy alone. The addition of MRI-targeted biopsy also led to 458 upgrades—changes in diagnosis to a more aggressive cancer, based on analysis of the biopsy tissue.
The combined biopsy provided more accurate diagnoses.
Among the men who had a prostatectomy, systematic biopsy alone underdiagnosed about 40% of the cancers. MRI-targeted biopsy alone underdiagnosed about 30%. The combined biopsy underdiagnosed only 14.4%.
For the most aggressive cancers, systematic biopsy underdiagnosed 16.8% and MRI-targeted biopsy 8.7%, but combined biopsy underdiagnosed only 3.5%.
“Prostate cancer has been one of the only solid tumors diagnosed by performing systematic biopsies ‘blind’ to cancer’s location. For decades this has led to the overdiagnosis and subsequent unnecessary treatment of non-lethal cancers, as well as to missing aggressive high-grade cancers and their opportunity for cure,” says Pinto. “With the addition of MRI-targeted biopsy to systematic biopsy, we can now identify the most lethal cancers within the prostate earlier, providing patients the potential for better treatment before the cancers spread.”
