Faulty tests give false hope to prostate cancer victims

Half of patients have more aggressive tumour than first diagnosed

HALF of men who are told they have only ‘slow-growing’ prostate cancer turn out to have more aggressive tumours, warn scientists.

They say inaccurate testing often underestimates the likely progress of the disease.

It is only when the prostate is surgically removed that doctors can tell for sure how much treatment patients will need.

The researchers found that more than half of a group of men whose cancers were initially classified as slow-growing actually had more dangerous tumours. In most cases they will have undergone active surveillance, where doctors monitor the tumour and symptoms before deciding whether more radical treatment was necessary.

But the new findings, published in the British Journal Of Cancer, suggest that biopsy samples taken at the outset often lead to cancers being wrongly classified.

Urological surgeon Greg Shaw, from the Cancer Research UK Cambridge Institute, said: ‘Our results show that the severity of around half of men’s prostate cancers may be underestimated when relying on tests before surgery.

‘This highlights the urgent need for better tests to define how aggressive a prostate cancer is from the outset, building on diagnostic tests like MRI [magnetic resonance imaging] scans, and new biopsy techniques which help to more accurately define the extent of the prostate cancer.

‘This would then enable us to counsel patients with more certainty whether the prostate cancer identified is suitable for active surveillance or not.’

Slow-growing prostate cancers, known as ‘pussycats’, are very different from the more aggressive and dangerous ‘tiger’ variety.

In some cases, especially when a

‘We need better methods’

patient is older when diagnosed, he can live to the end of his normal lifespan without the ‘pussycat’ cancer becoming a threat.

An aggressive ‘tiger’, on the other hand, may spread quickly if it is not surgically removed or destroyed.

Biopsy samples examined under a microscope are used to rate pros- tate tumour aggressiveness on a ‘Gleason score’ ranging from two to ten. Scores of eight to ten are high-grade ‘tigers’.

Tumours are also staged according to how far they have spread, while PSA (Prostate Specific Antigen) scores are a guide to how well the cancer is being controlled.

The Cambridge scientists compared the staging and grading of more than 800 cancers before and after the patients had surgery to remove their prostate.

They found that of 415 patients whose cancer was classified as slowgrowing and confined to the prostate, just over half (209) were found to have a more aggressive disease than originally thought. Almost a third (131) had cancers that had spread beyond the prostate gland, which need much more treatment.

Professor Malcolm Mason, Cancer Research UK’s prostate cancer specialist, said: ‘At the moment the biopsy, MRI and PSA tests that we use to assess the severity of prostate cancers are the best methods we have but, as this study shows, they don’t always get it right.

‘Despite the limitations that this study shows, all evidence points to active surveillance being safe provided men are carefully selected.

‘But we need better methods of assigning a grade and stage so that no man has to unnecessarily undergo treatment, while making sure we detect and treat the cancers that really need it.’

Around 41,700 men in the UK are diagnosed with prostate cancer each year and nearly 11,000 die from the disease.

Dr I ain Frame, Director of Research at Prostate Cancer UK, said accurate diagnosis was ‘one of the biggest challenges’ facing medical specialists.