Prostate cancer: NMR determines aggressiveness

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  • Published: Apr 15, 2018
  • Author: David Bradley
  • Channels: NMR Knowledge Base
thumbnail image: Prostate cancer: NMR determines aggressiveness

Aggressive metabolites

Prostatic adenocarcinoma with perineural invasion By Nephron [CC BY-SA 3.0 or GFDL from Wikimedia Commons]

Nuclear magnetic resonance (NMR) spectroscopy could help solve a commonly intractable medical problem: how to determine the aggressiveness of prostate cancer. The new approach could help oncologists identify which tumours could be life threatening and need radical treatment. Writing in the journal Scientific Reports, Leo Cheng of the Massachusetts General Hospital (MGH) and colleagues describe how cellular metabolites present in seemingly benign prostate tissue from a prostate gland known to contain cancerous cells can reveal the grade and stage of the tumour as well as determine its risk of recurrence.

"Prostate cancer detection through elevated PSA (prostate-specific antigen) levels followed by prostate tissue biopsies often cannot differentiate between patients with early-stage, indolent disease and those with aggressive cancers," explains Cheng. "The additional metabolic information provided by magnetic resonance spectroscopy can help guide treatment strategy, both to prevent overtreatment of slow-growing tumours - a critical and widely recognized current issue - and to identify the aggressive tumours for which additional treatment should be considered."

Tumour differentiation

Researchers estimate that almost three-quarters of men given a diagnosis of prostate cancer following PSA screening and biopsy will most likely have a less aggressive form of the disease. After treatment, the outcome for those patients is very good and there will be little impact on their future health. However, some 17 percent of cases are much more aggressive and are potentially lethal. Traditional histological analysis of prostate gland biopsies can easily overlook the most informative tissues, classifies tumours based on their cellular structural appearance. As such, it cannot distinguish between potentially lethal tumours that need aggressive treatment and those that might best be monitored for changes over time.

Perhaps one of the problems with the current approach to diagnostics in prostate cancer is that once an elevated PSA level is observed and recognised as indicative of the presence of prostate cancer, a biopsy of the tissue, or rather, several biopsies are taken at from random sites within the gland. This means that there is some degree of chance in whether or not those biopsies will miss the spot in terms of plucking out the cancerous tissue for further testing. The MGH team's approaching using NMR, or as it is more often referred to in medical circles, magnetic resonance spectroscopy (MRS), will reflect biochemical activity within tissue and allows problems to be detected irrespective of the specific site of biopsy.

Retrospective analysis

To test the approach, the researchers analyzed samples of benign prostate tissues from more than 150 men with a confirmed prostate cancer diagnosis that had led to complete removal of the prostate gland. Since this was a retrospective study of patients diagnosed up to 15 year ago, the researchers had access to both pathological analysis of the entire prostate gland and the ultimate outcome for each patient.

Metabolic changes in a 82 benign samples were tested first to see if there were metabolic changes that reflected the key prognostic factors - tumour grade, stage (or how far it has spread), and the probability of recurrence. They then analyzed samples separately from the remaining 76 patients and found the same associations between metabolite levels, grade, stage, and recurrence risk. Indeed, the metabolic data allowed them to determine whether or not what seemed to be benign prostate tissue was from a gland carrying an aggressive or less aggressive tumour or tumours and the localisation of the malign tissue. One specific metabolite, myo-inositol, a known tumour suppressor, were seen to be elevated in the tumours of patients with highly aggressive cancers. This is perhaps unsurprising, but that finding nevertheless needs additional information before it can be seen as leading to anything like a definitive route to diagnosis and prognosis.

"Measurement of a tumour's metabolic activity in the initial biopsy, even in histologically benign tissue, could help to determine whether a patient should have a prostatectomy or, for those with less aggressive disease, could enter active surveillance with peace of mind," suggests Cheng. The researchers are now analyzing samples from more than 400 additional prostate cancer cases and working to refine the field of metabolites that provide information valuable for treatment planning.

Related Links

Sci Rep 2018, online: "Metabolomic Prediction of Human Prostate Cancer Aggressiveness: Magnetic Resonance Spectroscopy of Histologically Benign Tissue"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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