For men with prostate cancer that has spread, the organ where it has spread has a direct impact on how long they will survive, according to the outcome of a large analysis conducted at Duke Cancer Institute.

Men whose cancer has metastasized only to lymph glands survive the longest, while those whose cancer has spread to their liver have the worst prognosis. Those who have lung and bone metastasis fall in the middle.

Researchers studied data from nine phase III clinical trials involving the outcomes of 8,736 men with metastatic prostate cancer. All patients had undergone standard treatment with the chemotherapy drug docetaxel.

"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," said lead author Susan Halabi, Ph.D.

Halabi and her colleagues categorized the site of metastases into four groups: lung, liver (without lung), lymph nodes only, and bone with or without lymph nodes and no other organ metastases.

Almost 73 percent of the patients had bone metastases, and their overall median survival was slightly more than 21 months. Men whose lymph nodes were involved were the smallest subset at only 6.4 percent, but they had the longest median survival at about 32 months.

Men with lung metastases had a median survival time of 19 months, and represented 9.1 percent of the study population. Men with liver metastasis represented 8.6 percent of the patients, and had the worst median survival of nearly 14 months.

"With the large numbers we analyzed 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," Halabi said. "This information could also be used to help guide treatment approaches using either hormonal therapy or chemotherapy.

According to the National Cancer Institute, 220,800 men were diagnosed with prostate cancer in 2015, and about 27,540 died from the disease.

The study was published in the Journal of Clinical Oncology.