A study released Friday suggests that an immunotherapy drug being developed by Dendreon Corp. may prolong the lives of prostate cancer patients who also undergo chemotherapy, the company announced.

The findings were released at a New York symposium by Dr. Daniel Petrylak, an associate professor of medicine with Columbia University Medical Center, Dendreon said in a press release.

The study examined the effects of Provenge, a drug that is designed to stimulate a patient's immune system. Seattle-based Dendreon (NASDAQ DNDN) is developing Provenge as an initial treatment for men with prostate cancer who later receive docetaxel chemotherapy for their illness.

Petrylak tracked 82 prostate cancer patients who were administered either Provenge or a placebo before undergoing chemotherapy.

The median survival period for patients treated with Provenge was 34.5 months, while the median survival period for patients treated with a placebo was 25.4 months, the company said.

Provenge is in late-stage clinical development.