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."
The scientists said that in 50 per cent cases, doctors make wrong classification of the prostate cancer initially and later they turned out to be dangerous tumours. They said doctors did not give much heed to these patients until tests suggest their condition had worsened.
For the study, 847 men with prostate cancer were tracked. Out of the 415 who were initially told their cancer was slow-growing, 209 were found to have a more aggressive form of the disease.
Scientists are also calling for better diagnosis which can help prostate cancer victims.
Prostate cancer is the most common male cancer in the UK. Each year, 41,700 new cases are detected with 10,800 reported deaths.
Shaw said, "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."
Slow-growing prostate cancers are called pussycats, while the more aggressive and dangerous are called tiger. The 'tiger' may spread quickly if it is not surgically removed or destroyed.
The findings were published in British Journal of Cancer.