Accurate diagnosis of prostate cancer is an ever-present problem but, as Corinne Swainger discovers, new developments promise progress
Accurately diagnosing prostate cancer continues to be a major challenge due to the limited testing methods currently available. However, researchers are investigating new biomarkers and improved screening techniques that can accurately detect the cancer at an early stage, and identify which tumours are likely to be high or low-risk.
Initial screening tests for prostate cancer primarily include the digital rectal examination (DRE) and prostate-specific antigen (PSA) blood test. Although PSA screening can detect cancerous cell growth, it cannot show whether the growth is benign or malignant, or how aggressive it is. Based on initial PSA and DRE results, a biopsy is typically carried out to detect potential cancer in the prostate.
However, the PSA test is not completely reliable. While a higher PSA protein level can be a classic marker for prostate cancer, it can also be caused by an infection, a non-cancerous enlarged prostate or even recent exercise. Consequently, up to 70 per cent of men with raised levels of PSA do not actually have cancer (a false-positive result), while around 15 per cent with a normal PSA level will have prostate cancer (a false-negative result).
Increasing evidence is now pointing towards the harm of over-diagnosis and over-treatment of suspected prostate cancer, triggered by PSA results. In May, a US government panel said that men should not get routinely screened for prostate cancer using the PSA test. The panel found little evidence that PSA testing saves men’s lives and that it causes too much unnecessary harm from the treatment of tumours that would never have killed them. Such treatments include unnecessary prostate gland removal surgery.
Scientists have designed a blood test that reads genetic changes like a barcode and picks out aggressive prostate cancers
Other tests may be used for men diagnosed with early or locally advanced prostate cancer and these will depend on symptoms. Some men are found to have prostate cancer after being investigated for bone pain, using an isotope bone scan, CT scan or MRI scan.
At present, based on initial PSA results, physicians will confirm the presence and assess the aggressiveness of prostate cancer in a variety of ways, which may include a needle biopsy of the prostate, blood tests and radiological scans, such as X-rays, CT scans and MRI scans. However, experts say these methods are only moderately accurate. For example, a biopsy will fail to detect cancerous cells in approximately 5 to 10 per cent of men with prostate cancer.
But recent research has revealed new biomarkers and developed new tests for improved prostate cancer diagnosis. Biomarkers help to differentiate between the low and high-risk types of cancer, and are crucial to decide if and what type of treatment a patient needs.
Earlier this year, the US Food and Drug Administration approved a new urine test that measures a gene present in prostate cancer. The PCA3 (prostate cancer gene 3) is the first molecular test to help determine whether a man, who has received a negative biopsy result, needs a repeat biopsy.
Researchers at the University of Surrey are also developing a new urine test that measures levels of a protein called EN2. A study found that testing for the protein could accurately identify 66 per cent of men with prostate cancer and correctly rule out the disease in almost 90 per cent of men without the disease.
One of the researchers, Professor Hardev Pandha, says: “The prospect of an immediate result that doesn’t involve a blood test or an embarrassing examination may be helpful in getting more men with urinary symptoms to seek medical help.” However, the research is at an early stage and further study is needed.
In October, scientists announced they had discovered a new diagnostic marker for prostate cancer, Beta-2-syntrophin, which could help doctors to distinguish between low- and high-risk level disease.
In addition, scientists have recently designed a blood test that reads genetic changes like a barcode and picks out aggressive prostate cancers by their particular pattern of gene activity. Researchers believe the blood test could eventually be used alongside the existing PSA test at diagnosis to select patients who need immediate treatment. The test is unique because it measures changes in the pattern of gene activity in blood cells triggered by a tumour elsewhere in the body.
Prostate cancer factfile
IT’S BEEN A HARD DAY’S NIGHT
Men who work nights are almost three times as likely to develop prostate cancer as those who work day shifts, according to new research. They are also at much greater risk of a number of other types of cancer, with higher rates of tumours in the bowel, bladder and lungs. Night shifts are thought to harm the body through the suppression of melatonin, a hormone produced by the pineal gland in the brain that helps regulate when people sleep and when they wake up.
LINK WITH BREAST CANCER
Scientists have identified genetic links between prostate cancer and breast cancer. The risk of prostate cancer may increase in men who have a family history of breast cancer and/or ovarian cancer. Mutations of two genes, known as brca1 and brca2, can also result in higher risks of breast and ovarian cancer in women. For men who have a family history of breast cancer, genetic testing may therefore provide some information about whether they share the same high-risk genetic mutations.
NEW DRUGS TO BE LAUNCHED
Two new prostate cancer drugs for treating advanced cases of prostate cancer are being launched on to the market. In August, the US Food and Drug Administration approved the pill Xtandi for treating men with advanced prostate cancer that has returned or spread despite major medical treatments. Another drug, enzalutamide, which can help to extend survival and improve quality of life in men with advanced prostate cancer, is also due to be licensed in the UK early next year.
LACK OF AWARENESS SURVEY
A recent survey by Janssen Biotech in the United States reveals a significant lack of awareness in men about the facts of prostate cancer. A majority (93 per cent) of the men surveyed failed to correctly identify at least two of the key symptoms. The results also show that most of the men surveyed (63 per cent) believe they won’t be diagnosed with prostate cancer and more than half (52 per cent) believe that, if they are diagnosed, the disease will not be fatal.
SCOTLAND FOLLOWS REST OF UK
A drug that can extend the lives of men with incurable prostate cancer has been approved for use in Scotland, the only part of the UK where abiraterone was not available on the NHS. The Scottish Medicines Consortium has now given doctors the go-ahead to prescribe it. The drug was one of several medications said to have helped keep Lockerbie bomber Abdelbaset al-Megrahi alive after he returned to Libya.