Health

How reliable are blood tests for prostate cancer?

PSA is a protein made by the prostate, the walnut-sized gland located below the bladder, and the amount shed into the blood can give doctors an idea of how healthy it is
PSA is a protein made by the prostate, the walnut-sized gland located below the bladder, and the amount shed into the blood can give doctors an idea of how healthy it is

Q: Concerned about my frequent visits to the loo, a GP gave me a PSA blood test. This was normal for my age of 73 (1.4) but an examination found a small, hard lump and an MRI scan diagnosed prostate cancer. How reliable are PSA tests?

DF

A: Prostate cancer is the most common cancer in men — one in eight will be diagnosed with it. There have been calls for men to be screened for the disease from middle age, primarily using the prostate specific antigen (PSA) blood test, which you had.

PSA is a protein made by the prostate, the walnut-sized gland located below the bladder, and the amount shed into the blood can give doctors an idea of how healthy it is. However, this test is far from perfect as PSA levels can be raised by a range of factors, including exercise, sexual activity, an enlarged prostate, constipation and infection — as well as cancer.

As you discovered, it’s also possible to have a false negative result — where the test suggests there is no cancer, when there is. This is why physical examination is vital.

In your case, the cancer was detected because you’d had urinary tract symptoms that your doctor quite rightly wanted to investigate further.

However, a DRE (digital rectal examination) can only detect tumours in the front and back of the prostate — and 25 per cent of tumours occur elsewhere in the gland.

As far as screening goes, the most reliable option is magnetic resonance imaging (MRI), because it allows you to see into the gland. But one issue is its limited availability on the NHS.

Separately, researchers are looking at tests to detect DNA fragments of cancer in the bloodstream. My advice if you have symptoms or are 50 or over and decide you want to have your PSA levels tested, see your GP.

The best policy is that only those at higher risk are screened: this includes men with a first-degree relative (i.e. a father or brother) who’s been diagnosed with prostate cancer under the age of 65, and black men (who, for ill-understood reasons, are at higher risk).

I hope that your cancer is confined to the prostate, as is the case for at least 78 per cent of patients at the time of diagnosis.

If this is the case, the likely treatment is an operation to remove the gland. I wish you a speedy and smooth recovery.

A diet rich in calcium-containing foods should be part of your response to osteopenia
A diet rich in calcium-containing foods should be part of your response to osteopenia

Q: Is a daily calcium supplement a good idea following a diagnosis of osteopenia?

LL

A: This is a good question as there is much confusion about the term osteopenia (as opposed to osteoporosis), and even more about whether calcium supplements are advisable.

Osteopenia refers to the loss of bone mineral — mainly calcium — that we must all expect as years pass. It is a normal part of the ageing process, caused by the body reabsorbing calcium rather than it staying in bones where it keeps them strong.

It is not a medical diagnosis as such but rather a warning sign that your bone density is falling. This can progress to osteoporosis, where bone mineral density becomes lower than expected for someone of your age, increasing the risk of fractures.

Risk factors include being female (due to the drop in oestrogen during menopause)as well as age, body size, family history and medications such as glucocorticoids. A diet deficient in calcium and vitamin D is another factor.

A daily calcium supplement can help, particularly if it’s taken alongside a vitamin D supplement as this promotes the absorption of calcium. The suggestion is 1,000mg of calcium and 600IU of vitamin D.

There is strong evidence these supplements lower bone turnover by a fifth — a powerful mechanism to limit progress from osteopenia towards osteoporosis.

However, studies have shown taking calcium supplements long term may increase the risk of heart disease in some people. Therefore it is a decision to be taken after a consultation with your GP.

Eating a diet rich in calcium-containing foods — milk, cheese and green leafy veg — does not have this negative effect, so should be a priority for you in the meantime.

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