WASHINGTON (Reuters) - The U.S. Food and Drug Administration has approved Celsion Corporation's device to treat benign prostatic hyperplasia, the company said on Thursday.

Boston Scientific will distribute and co-market the treatment, called Prolieve, which uses microwave heat to soften prostatic tissues. A balloon catheter filled with warm water is then used to open the urethral stenosis, creating a "natural stent," Celsion said in a statement.

Columbia, Maryland-based Celsion said clinical trials showed three-quarters of those treated with its device experienced fewer symptoms after two weeks than those who took Merck's Proscar.

Dr. Bill Gannon, Celsion's vice president for clinical affairs, said the device required only topical anesthesia and produced minimal side effects and risks. A recent study showed 5 percent of patients who underwent the treatment needed to use a catheter afterward, he said.

While there are other heat-based prostate treatments on the market, the company said Prolieve's use of warm water, versus cold, and tissue compression were unique.

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