Stem cell treatment helped treat erectile dysfunction in some -- but not all -- prostate cancer surgery patients, a new study says.

It included 21 men who became impotent after surgery to remove their cancerous prostate. They received stem cell injections meant to restore damaged nerves. After a single stem cell injection, eight of the men regained sexual function and kept it for a year, NBC News reported.

The study was presented at a European Association of Urology meeting.

"What we have done establishes that this technique can lead to men recovering a spontaneous erection -- in other words, without the use of other medicines, injections, or implants," Dr. Martha Haahr of Odense University Hospital in Denmark, said.

The researchers plan to conduct a larger study.

"If it works in these men (who've had their prostate removed), it would also work in men with have been treated using chemotherapy and radiation," and may also help men with erectile dysfunction caused by aging, heart disease or diabetes, according to Haahr, NBC News reported.

"If it's as effective as we think, it could help many kinds of men," she said.