Researchers found that of nearly 3,300 men who underwent prostate cancer surgery, those who were given both general and regional anesthesia had a lower risk of seeing their cancer progress than men who received only general anesthesia.
Over a period of 15 years, about 5 percent of men given only general anesthesia had their cancer recur in their bones or other sites, the researchers said. That compared with 3 percent of men who also received regional anesthesia, which typically meant a spinal injection of the painkiller morphine, plus a numbing agent.
None of that, however, proves that anesthesia choices directly affect a prostate cancer patient's prognosis.
"We can't conclude from this that it's cause-and-effect," said senior researcher Dr. Juraj Sprung, an anesthesiologist at the Mayo Clinic in Rochester, Minn.
But, he said, one theory is that spinal painkillers -- like the opioid morphine -- can make a difference because they curb patients' need for opioid drugs after surgery. Those post-surgery opioids, which affect the whole body, may decrease the immune system's effectiveness.
That's potentially important, Sprung said, because during prostate cancer surgery, some cancer cells usually escape into the bloodstream -- and a fully functioning immune response might be needed to kill them off.
"If you avoid opioids after surgery, you may be increasing your ability to fight off these cancer cells," Sprung said.
The study, reported online Dec. 17 in the British Journal of Anaesthesia, is not the first to see a link between regional anesthesia and a lower risk of cancer recurrence or progression. Some past studies have seen a similar pattern in patients having surgery for breast, ovarian or colon cancer. But those studies, like the current one, point only to a correlation, not a cause-and-effect link, Sprung said.
Dr. David Samadi, chief of urology at Lenox Hill Hospital in New York City, agreed. "We have to be very careful about how we interpret these results," said Samadi, who was not involved in the new study.
One important issue, he said, is that the men in this study all had open surgery to remove their prostate gland.
But these days, the surgery is almost always done laparoscopically -- a minimally invasive approach in which surgeons make a few small incisions. In the United States, Samadi said, most of these procedures are done with the aid of robotic "arms."
Compared with traditional open surgery, laparoscopic surgery is quicker and causes less stress, blood loss and post-surgery pain, Samadi said. And in his experience, he said, patients' need for opioids after surgery is low.
Sprung agreed that it's not clear whether the current findings extend to men having laparoscopic surgery.
The findings are based on the records of nearly 3,300 men who had prostate cancer surgery between 1991 and 2005 at the Mayo Clinic. Half had been given only general anesthesia, while the other half had received regional anesthesia as well. In 83 percent of the cases, that meant a spinal block containing morphine.
The researchers weighed other factors, such as the stage of the cancer and whether a man received radiation or hormone therapy after surgery. In the end, having general anesthesia alone was linked to a nearly threefold higher risk of a cancer turning up in distant sites in the body over the next 15 years.
Still, only 3 percent to 5 percent of the men had a cancer recurrence. And, Samadi said, the risk is generally low with a skilled surgeon. He suggested that patients be more concerned about their surgeon's experience than the type of anesthesia.
Studies have found that prostate cancer patients treated by more experienced surgeons tend to have a lower risk of recurrence, Samadi said. They also have lower rates of lasting side effects, such as erectile dysfunction and incontinence.
"It's not the robot," Samadi said. "It's the experience of the surgeon."
To prove that regional anesthesia directly affects cancer patients' prognosis, "controlled" studies are needed, Sprung said. That means randomly assigning some surgery patients to have general anesthesia only, while others get regional anesthesia as well.
For now, Sprung said, the decision about whether to use a spinal painkiller during surgery should be based on other factors, such as its potential to limit post-surgery pain.
The American Cancer Society has more information on prostate cancer surgery.