Experts believe they can develop a genetic screening test that can tell doctors which men with prostate cancer need aggressive treatment.
Early trial results for Cancer Research UK suggest men with high levels of cell cycle progression (CCP) genes have the most deadly tumours.
The CCP test could potentially save men with milder forms of the disease from unnecessary treatment.
Large-scale studies are now needed, the Lancet Oncology journal reports.
Prostate cancer is the most common cancer in men in the UK, with new cases diagnosed in around 37,000 men every year.
At present, doctors can struggle to predict how aggressive tumours are and rely on tests and examinations that can be less than reliable.
For example, one of the tests currently used - the Prostate Specific Antigen (PSA) test - can give a worrying result even if a cancer is not present.
Cancer Research UK estimates that about two-thirds of men with an elevated PSA level (measured as > 4ng/ml) will not have prostate cancer but will suffer the anxiety, discomfort and risk of follow-up investigations.
It's for this very reason that UK experts have recommended against a screening programme for prostate cancer.
But experts from Queen Mary, University of London, hope their new CCP test - alongside existing tests like PSA - could be used routinely in the clinic to overcome this problem.
Professor Jack Cuzick, who led the research, said: "Our findings have great potential. CCP genes are expressed at higher levels in actively growing cells, so we could be indirectly measuring the growth rate and inherent aggressiveness of the tumour through our test.
"We already know that CCP levels can predict survival for breast and, more recently, brain and lung cancers.
"It's really encouraging that this could also be applied to prostate cancer, where we desperately need a way to predict how aggressive the disease will be."
His study, which included 703 men with prostate cancer, found CCP could predict likely disease outcomes.
In the study, men with the highest levels of CCP genes were three times more likely than those with the lowest levels to have a fatal form of prostate cancer.
And for patients who have had surgery to remove their prostate, those with the highest CCP levels were 70% more likely to have a recurrence of the disease.
Dr Helen Rippon, head of research management at the Prostate Cancer Charity, said the findings were promising but needed replicating in larger trials before the test could be considered for routine use.
"It will therefore be some time before men diagnosed with prostate cancer will see any direct benefit from this research," she said.