Where prostate cancer spreads in the body has a direct impact on survival, research has shown.

Scientists have been able to map typical survival times to specific organ sites.

The study found that patients whose tumours had only spread to the lymph nodes had a best prognosis of 32 months.

Those whose cancer had reached the liver had a life expectancy of two years.

Spread to the bones was associated with a survival time of 21 months and to the lungs of 19 months.

The research was based on data from nine large Phase III clinical trials involving 8,736 men with advanced prostate cancer. All had undergone standard treatment with the chemotherapy drug docetaxel.

Professor Susan Halabi, from Duke University, in the US, said: "Smaller studies had given doctors and patients indications that the site of metastasis in prostate cancer affects survival, but prevalence rates in organ sites were small, so it was difficult to provide good guidance.

"With the large numbers we analysed in our study, we were able to compare all of these different sites and provide information that could be helpful in conveying prognosis to patients. This information could also be used to help guide treatment approaches using either hormonal therapy or chemotherapy."

Nearly 73% had experienced metastasis, or spread, to the bones. Men with lymph involvement only made up the smallest group, accounting for just 6.4% of the total.

Patients with liver metastasis represented 8.6%, while those with lung disease made up 9.1%.

"These results should help guide clinical decision-making for men with advanced prostate cancer," said Prof Halabi. "They also suggest that prognostic subgroups should be considered for investigational therapies that are tested in clinical trials."

For each metastasis category, the scientists calculated a "median" survival value - the middle point in a range of survival times.

The findings are published online in the Journal of Clinical Oncology.