Boston Scientific Corp. plans to grow its burgeoning urology business with a novel Minnesota invention called the Rezum system, which is used to treat a symptomatic enlarged prostate with heat that is transferred entirely through water vapor.

The Massachusetts-based medical device company on Wednesday said it plans to acquire Maple Grove’s NxThera in a deal valued at up to $406 million, including milestone payments and an existing 15 percent stake that Boston has in NxThera.

“This is great for patients and urologists, and it’s great for employees and investors,” NxThera CEO Bob Paulson said Wednesday. Boston Scientific “can help expand access at a much more rapid pace than we can, just because they are a large company. And from an investor perspective, and an employee perspective, this is a very attractive purchase price.”

The deal is expected to happen in the second quarter, pending approvals. Upon closing, the companies expect to spin out a new company that would investigate a new application of the Rezum technology for prostate and kidney cancer, which has so far been tested in 30 patients, Paulson said.

The Food and Drug Administration cleared the Rezum system in 2015 to treat symptomatic BPH, or benign prostatic hyperplasia, which is an enlargement of the prostate gland that becomes more common as men get older.

BPH affects an estimated 110 million men worldwide, including more than 12 million symptomatic men in the United States. Symptomatic BPH can cause pain, block the flow of urine from the bladder, and lead to problems in the urinary tract and kidneys.

The Rezum system “helps patients with a minimally invasive approach while reducing the cost and unwanted side effects” associated with first-line BPH therapies like maintenance medications, said Dave Pierce, president of urology and pelvic health for Boston Scientific, in a statement.

Drugs that reduce testosterone or relax muscles are often used as a first-line therapy for BPH, but Paulson said as many 60 percent of men stop using the drugs within a year because of side effects.

The Rezum system is intended as an alternative first-line treatment that can allow men to delay or avoid the more invasive treatment for serious symptomatic BPH, which is prostate surgery.

A NxThera-sponsored study published in this month’s Journal of Urology reported that three years after treatment with the Rezum system, BPH patients had rates of clinical progression that were five times lower than reported rates of patients treated with daily, long-term medications. More than 20,000 patients have been treated with the system, which is typically done in a doctor’s office.

The system works by heating water vapor and delivering it to the enlarged gland, where it transfers heat to the tissue to kill the cells causing the symptoms.

The body’s immune system then cleans away the dead tissue over time. Using heated water vapor avoids inflammation that might happen from applying heat with other methods, Paulson said.

He declined to comment on the cost of the Rezum, which includes a durable capital component and single-use disposables.

The treatment is covered by Medicare and many private insurers, so the price to the patient depends on their coverage.

Paulson said Boston Scientific is likely to commercialize the system in the U.S. and internationally, where growth could be swift.

“This is a global health condition that affects men everywhere,” Paulson said. “We’ve only begun to scratch the surface … outside the U.S. In many other countries, the only options are drugs or surgery.”