Prostate cancer is one of the most common forms of cancer in Norway, but so far the clinical diagnostic tools have not been able to say much about where in the prostate gland the cancer is, or its aggressiveness in individual patients. A new method developed at the MR Centre may give a clearer answer.
By combining magnetic resonance imaging (MRI) with MR spectroscopy (MRS), PhD candidate Kirsten Margrete Selnæs has developed a method which helps localise cancer in the prostate gland, and how far the cancer has developed. The method can also give a clearer idea of how aggressive the cancer is, which is important with regards to treatment.
“One of the problems in prostate cancer is to know who has an aggressive form and needs immediate treatment, and who can wait,” Selnæs explains.
She used two different MR methods to answer the question of aggressiveness. First tissue samples from the prostate gland are studied outside the body (ex vivo).
The sample is run through an MR spectrometer which results in a spectrum – or metabolic profile. The researchers then look for values that are prominent in the aggressive cancer forms.
In the ex vivo tests the researchers found two possible biomarkers for prostate cancer aggressiveness: the metabolites citrate and spermin.
Then the same test is done on patients in the body (in vivo), although this gives fewer details. Nonetheless, Selnæs found that the results from the ex vivo tests correlate to those done in vivo. This could lead to a more detailed diagnosis before a potential removal of the prostate gland.
“Until now we have not been able to differentiate the aggressive from the less dangerous cancer in the clinic. But we now hope to be closer to a method for differentiating between the two without having to operate,” Selnæs says.
“With the screening programme for prostate cancer, many cases are discovered which will never develop into actual illness. But so far there has not been a method to confidently determine who will die from the cancer, and who do not even need treatment.”
A detailed map
Selnæs has also compared the MRS results with MR images to get a detailed overview over where the tissue samples come from.
Normally when collecting tissue from the prostate gland, one takes a biopsy, and although it is known whether the sample comes from for example the right or left side of the prostate gland, one does not know any more details.
By combining MRI with MRS in vivo in the patient, it is possible to give the urologist more precise data for where the biopsy should be taken – the difference is akin to trying to navigate from a photograph compared with a map with precise GPS coordinates.
The way it is done is to use the MR images to identify suspicious-looking areas and then run MRS tests on these. If the MRS results also show a typical ‘cancer-result’, it is more certain that it is actually cancer – there are more proofs.
To arrive at this result, Selnæs made us of a new method developed at the Institute for Laboratory medicine, Children’s and Women’s Health (LBK), where one can determine exactly where in the prostate gland the samples are gathered from. This enables the comparison of visual images from MR with the MRS results.
The research is in no way over although Selnæs has completed her PhD. The bio-marker results will be validated through larger patient studies, and an active monitoring study is planned with patients who according to clinical evaluation can wait with treatment.
“We will do an MR scan when they start the study, and after a year when they are back for their routine control. And we will look at whether there is something in the MR images or MR spectres that can tell us something about who should continue with monitoring,” Selnæs explains.
Kirsten Margrete Selnæs will defend her thesis on 25. September 2012 at 12.15 in the Auditorium at MTFS, St. Olavs Hospital.
In connection with the defence, there will be a pre-defence seminar on prostate cancer and MR the day before, on the 24. September.
|Magnetic resonance imaging (MRI) is a method for imaging ‘slices’ of the body through the use of radio waves and magnetic fields, which have no known harmful biological effects.
Magnetic resonance spectroscopy (MRS) is a method for looking at the metabolism in cells and gives information about the cells’ biological reactions.
Metabolites are molecules that take part in, or are made from, the metabolism in the cells.
Prostate cancer is a malign tumour in the prostate gland and is the most common form of cancer among men in Norway.