Prostate cancer 'easier to detect' with new type of MRI

A new type of magnetic resonance imaging or MRI appears to be measurably better at spotting prostate cancer tumors than the current method, according to the results of a new study. The authors say the finding may also have significant implications for the treatment of prostate cancer.

A new type of MRI promises to detect prostate cancer tumors more accurately than the current standard.

Writing in the journal Prostate Cancer and Prostatic Diseases, a team led by the University of California San Diego (UCSD) School of Medicine, describes how the new MRI technique - called restriction spectrum imaging-MRI (RSI-MRI) - produces measurably better results in detecting prostate cancer tumors than the current standard, contrast-enhanced MRI.

This new approach is a more reliable imaging technique for localizing tumors. It provides a better target for biopsies, especially for smaller tumors.

This offers a non-invasive way to assess more accurately the extent of the tumor and perhaps even predict its grade. This helps doctors decide more precisely the most effective and appropriate treatment.

New MRI technique picks up water diffusion in tissue rather than blood flow

Contrast-enhanced MRI, the current standard for detecting and diagnosing prostate cancer, uses a substance that is injected into the patient that the MRI scanner then picks up to highlight blood flow. The technique offers a chance to spot tumor type and shape because of the differences in blood flow between healthy and cancerous tissue, which typically demands more blood.

However, not all tumors differ sufficiently from surrounding healthy tissue in terms of blood demand, and in these cases, they are hard to spot using contrast-enhanced MRI.

Because of this limitation, researchers have recently been looking at another type of MRI called diffusion MRI that picks up the diffusion of water in tissue. Diffusion MRI is a standard technique for brain scanning.

Another feature of tumors is that their tissue is denser than healthy tissue, and this affects the ease with which water can permeate it.

However, as it stands, diffusion MRI distorts the location of prostate tumors - by as much as half an inch or 1.2 cm - because of a problem called "magnetic field artifacts." This amount of magnetic distortion is enough to cause problems for surgeons, who need to know how far a tumor might extend beyond the prostate, for instance, how deeply it is enmeshed with nearby nerve bundles.

RSI-MRI measurably better than contrast-enhanced MRI for detecting prostate tumors

In their paper, the authors describe results of comparing contrast-enhanced MRI and RSI-MRI in 28 patients with prostate cancer who underwent both types of scan prior to radical prostatectomy.

They conclude that RSI-MRI corrects for the magnetic field distortion of diffusion MRI sufficiently to make it useful and more effective than contrast-enhanced MRI for tumor location and sizing in prostate cancer.

In another paper, to be published in the journal Frontiers in Oncology, the team reports how RSI-MRI may also be able to predict the grade of a tumor. This is because the amount of water cancer cells can take into their nuclei differs with tumor grade.

Being able to predict tumor grade using non-invasive imaging could spare some patients from aggressive prostate surgery and allow them to be monitored with scans instead.

The study was partly funded by the National Institutes of Health/National Institute of Biomedical Imaging and Bioengineering, the Department of Defense, Prostate Cancer Research Program, the American Cancer Society and the Clinician Scientist Program at UCSD.

According to the American Cancer Society (ACS), about 1 man in 38 will die of prostate cancer in the US, where the disease is the second leading cause of cancer death in men, after lung cancer.

The ACS estimate that in 2015, about 220,800 new cases of prostate cancer will arise in the US, and there will be about 27,540 deaths to the disease.

The chances of surviving prostate cancer reduce dramatically once it spreads to other parts of the body. Tools that better anticipate this stage of the disease can make a big difference. In September 2014, another report showed how a team is developing a device that can sort cancer cells circulating in the bloodstream to better predict cancer spread.

References:

1.  Novel technique for characterizing prostate cancer utilizing MRI restriction spectrum imaging: proof of principle and initial clinical experience with extraprostatic extension, RA Rakow-Penner, et al., Prostate Cancer and Prostatic Diseases, doi:10.1038/pcan.2014.50, published online 6 January 2015, abstract.
2.  University of California - San Diego news release accessed 7 January 2015 via EurekAlert.