13 May 2013
ByAppeared in BioNews 704
A genetic test released in the USA claims to be able to score the aggressiveness of prostate cancer before medical intervention, helping men with the condition decide if and when to start receiving treatment.
Researchers at the University of California, San Francisco (UCSF) showed that data produced from the test can help assess the level of risk presented by a prostate tumour and increase the number of cases where men can delay or avoid treatment.
While many prostate tumours progress slowly, allowing men to actively monitor the condition without the need for treatment, around one in five men with prostate cancer are diagnosed with fast growing tumours that require prompt medical intervention.
Current treatment options carry significant side effects, however, and many men are hesitant to choose active monitoring. For those with less aggressive forms of the cancer, however, treatment at that time may not be necessary.
'It's very hard to tell a surgeon "I'd like to leave a cancer in place"', said Dr Jonathan Simons, president of the Prostate Cancer Foundation, a research and advocacy organisation in the USA. 'Having objective information is going to help a lot of patients make that decision'.
There is currently no single test for prostate cancer, which is diagnosed through a combination of blood tests, physical examinations and biopsy. Decisions about treating prostate cancer are made using a combination of clinical observations including prostate-specific antigen screening (PSA), which may detect early stage prostate cancer but is not routinely offered as results can be unreliable, and the Gleason scale, a grading system based on the microscopic appearance of tumours.
Genomic Health says its Oncotype DX test provides patients with more information than what is currently available under the PSA and Gleason regime. The test analyses 17 genes associated with prostate cancer from a biopsy sample and produces a result on a scale from 0 to 100, called the Genomic Prostate Score (GPS). When combined with other clinic measures, the GPS can help determine the aggressiveness of the tumour prior to intervention.
The UCSF study, which analysed biopsies stored from 412 patients assessed as having low or intermediate risk prostate cancer but who chose to undergo surgery, showed the Oncotype DX scored one third of the samples as low risk, compared to between five and ten percent using existing techniques. For these men treatment may have been unnecessary.
'Now men can have greater confidence in their treatment plans, knowing decisions are being made based on their individual biological information', said Howard Soule of Prostate Cancer Foundation. 'For men with prostate cancer, the ability to more precisely define their risk level for aggressive disease is a significant leap forward'.
Some experts are concerned about the impact this new information will have on patients, however. 'We throw all these numbers at them. Are they really going to make a better decision?' said Professor Matthew Cooperberg, at UCSF, which has received funding to investigate how men diagnosed with prostate cancer make decisions about treatment.
Others are concerned about the subjectivity of interpreting the GPS. 'The question is, what's the magnitude of difference that would change the patient's mind?' said Professor Bruce Roth, a cancer specialist at Washington University in St. Louis.
The release of Oncotype DX adds to a range of genetic tests that are being developed for prostate cancer. Myriad has also released a genetic test, Prolaris, which measures the aggressiveness of prostate cancer tumours.