A robotic system being used in surgery at University of Miami (Sylvester Comprehensive Cancer Center)

Robotic-assisted procedures have now become ubiquitous in some kinds of surgeries. What once was seen as a technological marvel is commonplace in many hospitals.

But studies in recent years have shown robotic surgery performs no better than traditional surgery — even though it comes at a steeper cost to the overall health-care system.

The latest comparison study was published in the medical journal Lancet on Thursday and shows there were no major differences in outcomes or complication rates in operations for bladder cancer. On the plus side, robotic surgery — because it generally requires smaller incisions — resulted in less blood loss, less need for blood transfusion and slightly shorter hospital stays. The study showed robotic surgery did not cause more complications or higher cancer recurrences — a concern that has been raised by critics in the past.

On the minus side, robotic surgery required a lengthier time on the operating table, the study found. And the robotic system used in almost all hospitals costs roughly $2 million to acquire and is expensive to run.

Dipen J. Parekh, lead author on the study, said the findings point to the need for rigorous study of surgical innovations like robotic surgery before they receive widespread adoption. "Just because something is new doesn’t necessarily mean it’s better," said Parekh, director of robotic surgery at the University of Miami Miller School of Medicine. At a time when health-care costs are soaring, he said, it does not always make sense to have hospitals buy and use an expensive system when its effectiveness in many types of operations has not undergone thorough vetting. "We need to be making evidence-based decisions instead of marketing-based decisions, and to do that, you need data like what we produced in this study."

In robotic surgeries, the machine allows surgeons to control robotic arms from a console and magnifies the surgical site on a large screen. For some procedures, the machine's narrow arms and video scoping system allow the surgeon to make smaller incisions. The machines have become especially popular for gynecological and urological surgeries.

Comparison studies on different types of surgeries in recent years have resulted in similar findings to Thursday's. A 2017 study over a 13-year period — comparing robotic and non-robotic laparoscopic procedures for kidney cancer — found no statistical difference in outcome or length of hospital stay, even though the robotic operations cost on average $2,700 more per patient.

Another 2017 study, published in JAMA, found no statistically differences in the rate at which robotic or non-robotic surgeries for rectal cancers — operations that begin in both cases as minimally invasive surgeries — required a later more invasive open surgery. The main difference found in that study was also one of cost.

The new Lancet study is the most rigorous comparison to date for a specific type of surgery called cystectomy used for bladder cancer. The researchers conducted a randomized study of 350 patients across 15 institutions.

One challenge that Parekh — and his 31 co-authors on the study — faced was patients pressing to have their operations be done using a robotic device because of the marketing and a widespread perception that robotic surgery is more high-tech and somehow better.

"We tried to tell them the truth that there’s no evidence either way is any better and that’s the whole reason we were doing the study, but some of them insisted on the robotic surgery so we couldn’t include them since the whole purpose of the study was to randomize it," said Parekh, who noted the response highlights the effectiveness of current marketing for robotic surgery.

Alessio Pigazzi, a surgery professor at the University of California at Irvine, called the Lancet study important because it is the first randomized trial for cystectomies. "It shows some short-term benefits which I think are important. And it assures us on some of the fears from the past about robotic surgery of this type," he said. "But it's not a win for all. It shows that open surgery remains a good option for those experienced in it. The experience of the surgeon is what matters in many cases."

Benjamin Chung, an Stanford University associate professor of urology, said the study appears to validate robotic assistance for this type of surgery. For both sides — surgeons who are supportive and critical of robotic surgery — he said, studies like this point to the fact that more research will help determine the role robotic surgery should play in the future. "We need more studies to further the data that exists so far both on effectiveness and cost."