DNA test for prostate cancer relapse shows promise

A blood test for men with prostate cancer could indicate whether their cancer is likely to recur after treatment, and if so, how aggressively, say researchers from the University of Pittsburg School of Medicine, USA.

A study to investigate whether prostate cancer relapse can be predicted by looking at genetic abnormities using tissue samples from tumours as well as from neighbouring tissues and blood samples had promising results. It could mean that less invasive tests could be used after a patient's initial treatment to see if further treatment is needed. Patients could be spared further aggressive treatments if their cancer is found to be slow-growing and therefore unlikely to cause death.

Dr Jianhua Luo and his colleagues analysed the genomes of 104 prostate tumour samples, 85 blood samples and 49 samples of benign prostate tissue adjacent to tumours to identify copy number variations (CNVs). A CNV represents an abnormal number of copies of one or more sections of DNA. Samples from all three tissue/blood groups showed CNVs, some with similar deletion and amplification patterns. Using this data, the researchers were able to build a prediction model to identify patients at risk of relapse.

The researchers found that CNVs from prostate tumour tissue could predict the chance of relapse with significant accuracy, at 73 percent. Similarly, CNVs from these tissues could predict cancer aggression with 75 percent accuracy - although as the study was conducted in patients who had already undergone the removal of all or part of the prostate, the test did not identify benign tumours from aggressive ones before treatment.

Blood samples also had high predictive accuracy - at 81 percent for relapse and 69 percent for aggression; as did neighbouring benign prostate tissue samples - at 67 percent for relapse and 77 percent for aggression.

'For a patient already having a radical prostatectomy, CNV analysis on the tumour or blood sample may help to decide whether additional treatment is warranted to prevent relapse. Despite some limitations, including the need for high quality genome DNA, CNV analysis on the genome of blood, normal prostate, or tumour tissues holds promise to become a more efficient and accurate way to predict the behaviour of prostate cancer', said Dr Luo.

Reporting on the study, the Daily Mail said a blood test is likely to be several years away. The results of the study will need to be validated with further research and an inexpensive blood test developed before such a test could reach the market.