Although the findings may help inform decisions about cancer surgery, a gold-standard trial comparing the two methods of prostate removal head-to-head is still lacking, researchers said.

"We don't really have that high-level evidence… that can tell us that one is better than the other, or how one is different than the other," said Dr. Paul Nguyen, who treats prostate cancer at Brigham and Women's Hospital in Boston.

For example, even if some complications such as bleeding happen less frequently with robotic surgery, it's possible men who get that procedure may have more sexual or urinary problems further down the road.

Even without rigorous comparison data, the da Vinci Surgical System, sold by Intuitive Surgical, has become especially popular for prostate and gynecological surgeries in recent years and is heavily advertised by hospitals that use it.

The new study "makes us need to sit back and evaluate what we're getting for the extra cost," Nguyen, who wasn't involved in the research, told Reuters Health.

"If it's not better, or not better enough, it may not be worth it."

The robots run for an average of just under $1.5 million, not including the cost of long-term maintenance and extra parts.

Dr. Simon Kim of the Mayo Clinic in Rochester, Minnesota and his colleagues found the average prostate surgery done using a robot was billed at about $10,400, including all hospital fees. That compared to an average cost of just under $8,900 for standard so-called radical prostatectomy.

Data came from two large hospital and patient surveys conducted in the United States. In 2006 to 2008, about 20,400 men in those studies had their prostates removed using robotic surgery and 9,400 had "open" robot-free procedures.

Men typically stayed in the hospital for one day after robotic surgery compared to two days after a standard procedure. And post-op complication rates were eight percent in the robotic group versus 11 percent in the standard surgery group, according to findings published in the journal European Urology.

Dr. Yair Lotan, a urologist from The University of Texas Southwestern Medical Center in Dallas, said the findings are consistent with past results that suggest small reductions in some prostate complications with robotic surgery.

But, he told Reuters Health, "There haven't been well-demonstrated advantages in terms of cancer outcomes or even quality of life measures."

Studies have also found costs add up faster for various types of robotic surgery than with standard surgery (see Reuters Health story of August 22, 2012).

Angela Wonson, a representative for Intuitive Surgical, pointed out some limitations to the information included in the new research.

"Clinical benefit to the patient must be at the center of any discussion of cost," she told Reuters Health in an email. "Fewer complications and lower readmission rates will decrease the overall cost burden to both patients and the healthcare system. The costs of post-operative complications and readmissions, which these data do not capture, are significant."

Nguyen said that at this point, surgical method typically comes down to patient preference. And it may not even be the most important decision men make, he added.

"If a patient does need surgery, I wouldn't choose just on the basis of the robot versus the open, but a lot more on the surgeon, and the experience of the surgeon," Nguyen said.

SOURCE: bit.ly/Qe7IEr European Urology, online August 20, 2012.

• A Permanent Economic Emergency