Surgery death rates have dropped nationwide over the past decade, says a University of Michigan Health System study.

The Michigan study, which appeared in the New England Journal of Medicine earlier this summer, shows surgery mortality dropped substantially for eight different high-risk surgeries performed on 3.2 million Medicare patients from 1999 to 2008.

More patients are surviving open-heart surgery and replacement of diseased aortic valves, but research shows that cancer surgeries have seen the most dramatic improvement in safety. Due in large part to high-volume hospitals and their expertise, death rates had a 67 percent decline in deaths for pancreatectomy; a 37 percent decline in deaths from cystectomy, surgery to remove the bladder; and a 32 percent drop in esophagectomy mortality.

"Patients should take solace in knowing that all high-risk surgeries have become safer in the last decade," says lead author Dr. Jonathan F. Finks, clinical assistant professor of surgery at the University of Michigan Health System. "In cancer surgery, in particular, mortality has dropped in large part because more patients are having their surgery in safer, higher-volume hospitals."

One of the more interesting findings by Michigan's Center for Healthcare Outcomes and Policy is that hundreds of low-volume U.S. hospitals stopped doing high-risk cancer surgery.

For example, the number of Medicare patients needing surgery to treat pancreatic cancer increased by 50 percent, but the number of hospitals performing the surgeries decreased by 25 percent, from 1,308 hospitals to 978.

As a result, the volume of surgeries a hospital may do in a year rose from five cases of pancreatectomies a year to 16.

There have been numerous efforts in the U.S. to concentrate selected operations at high-volume hospitals. The Leapfrog group, a consortium of large corporations and public agendas that buy health care largely for their employees, has been among the most prominent advocates of volume-based referrals.

In 2000, it placed a minimum volume standard on hospitals for several surgical procedures to guide where employees get medical care.

The Michigan analysis shows volume-based referrals have been successful for certain surgeries, but the effort to make surgery safer takes more than one fix.

"For some procedures, strategies such as operating room checklists, outcomes measurement programs, and quality improvement collaboratives are likely to be more effective than volume-based referral," says Dr. John Birkmeyer, director of the Michigan Center for Healthcare Outcomes and Policy.