By Roni Caryn Rabin

New York Times News Service

Robotic surgery was never approved for mastectomy or any other cancer-related treatment, but that has hardly deterred doctors in the operating room. The equipment is widely used to operate on patients with various malignancies, from breast cancer to prostate cancer.

Yet there have long been questions about how well doctors are trained on the machines, and whether the devices are better for patients than traditional methods.

Now the Food and Drug Administration has warned there is no evidence cancer patients receiving robotic procedures live longer than those who have traditional procedures. And some research shows that patients with cervical cancer fare worse.

“We want doctors and patients to be aware of the lack of evidence of safety and effectiveness for these uses so they can make better informed decisions about their cancer treatment and care,” said Dr. Terri Cornelison, assistant director for the health of women at the agency’s Center for Devices and Radiological Health.

Robotic systems have been on the market for more than 15 years, and have been used for cancer surgery for much of that time. The machine’s tower, which is positioned over the patient, looks a bit like a multiarmed “Star Wars” droid. Three of its arms hold surgical devices, while a fourth holds a camera.

The robot’s arms are controlled by a computer that replicates the movements of the operating surgeon, who manipulates the robot’s controls while looking at a monitor that provides a magnified, high-definition image of the operating site.

The FDA noted the findings of two studies published last year in the New England Journal of Medicine.

One of them was a clinical trial that was stopped early after investigators found that women with cervical cancer who had minimally invasive hysterectomies, including robotically assisted procedures, experienced four times as many cancer recurrences and six times as many deaths, compared with patients who had the more traditional procedure.

The trial’s findings were especially striking because the surgery, a radical hysterectomy, usually cures patients with cervical cancer, said Dr. Pedro Ramirez, lead author of the paper and director of minimally invasive surgical research at the M.D. Anderson Cancer Center in Houston.

A second study funded by the National Institutes of Health used a database to compare the outcomes of 2,461 women with cervical cancer who had different types of surgery. Four years after the operation, 9.1 percent of those who had minimally invasive surgery had died, compared with 5.3 percent of those who had open surgery.

Yet many physicians continue to recommend robotic surgery to patients, despite the evidence of harm. “Several surgeons have said to me, ‘I can’t find a flaw in your study, but I just can’t stop doing it,’” Ramirez said.

It is not clear why cervical cancer outcomes were worse after minimally invasive surgeries. Ramirez suggested that the instruments used to manipulate the cervix and uterus may cause cancer cells to spread.

Another possibility is the carbon dioxide pumped into the abdomen during robotic and other minimally invasive procedures — it provides working and viewing space for the surgeon — may increase the likelihood of cancer cells implanting, Ramirez said.

The FDA’s warning was not limited to cervical cancer: Robotic surgical devices are not authorized for prevention or treatment of any cancer, nor are they approved for mastectomy (removal of the breast), the agency said.

The agency also urged health care providers “to complete the appropriate training” needed for performing robotic surgery, and urged patients to ask doctors about their training and experience, as well as about their patients’ outcomes.

In 2000, the agency allowed the sale of one of the first robotic surgery systems, the da Vinci Surgical System, under a process called “premarket notification,” which is often used to bring medical devices on to the market without the rigorous safety and efficacy trials required for new drugs.

Under premarket notification, devices are “cleared” for use on the grounds that they are similar to devices already available. The da Vinci system is cleared for some urological and gynecological procedures, among others.

A similar robotic device, the Senhance Surgical System, was approved for gynecological and colorectal surgery, among other procedures.

But the efficacy of either system for cancer treatment has not been evaluated by the FDA. And none of the systems has been cleared for mastectomy, which has become a frequent use.

So why are these machines allowed in cancer surgery at all? According to a spokeswoman, the FDA does not regulate the practice of medicine.