Tests to grade and stage prostate cancer underestimated the severity of the disease in half of men whose cancers would have been classified as ‘slow growing’ in a study* published in the British Journal of Cancer.

“Our results show that the severity of up to half of men’s prostate cancers may be underestimated when relying on tests before they have surgery." - said Mr Greg Shaw, study author.

Cancer Research UK scientists from the University of Cambridge compared the staging and grading of over 800 men’s cancers before and after they had surgery to remove their prostate.

They found that in the 415 men whose prostate cancer was classified as slow growing and confined to just the prostate after an initial biopsy, half (209) – when assessed again after surgery – had more aggressive cancer than originally thought.

And almost a third (131) had cancers that had spread beyond the prostate.

Mr Greg Shaw, a urological surgeon and one of the study authors based at the Cancer Research UK Cambridge Institute, said: “Our results show that the severity of up to half of men’s prostate cancers may be underestimated when relying on tests before they have 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 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.”

“Whilst active surveillance would seem to be a safe approach for some men, nearly a third will end up needing surgery or radiotherapy within five years.”

Prostate cancer is the most common cancer in men in the UK with around 41,700 new cases diagnosed every year.

There were around 10,800 deaths in the UK from prostate cancer last year**.

Professor Malcolm Mason, Cancer Research UK’s prostate cancer expert, 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 so far 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 at the same time making sure we detect and treat the cancers that really need it.”

References

* Shaw GL et al. Identification of pathologically insignificant prostate cancer is not accurate in unscreened men (2014) British Journal of Cancer

**Based on 2011 incidence and mortality information for prostate cancer in the UK

Source: Cancer Research UK