In the late 1970s, Harold Luft, Ph.D., of the University of California at San Francisco, and his colleagues observed that hospitals performing 200 or more surgical procedures a year had 25% to 41% fewer patient deaths than hospitals performing fewer procedures. Their landmark study appeared in the Dec. 20, 1979, issue of the New England Journal of Medicine.
Since then, numerous studieson procedures ranging from coronary artery bypass surgery to colon cancer surgeryhave come to similar conclusions: Hospitals that perform more surgical procedures (i.e., high-volume hospitals) tend to have better outcomes than hospitals that perform fewer such procedures (i.e., low-volume hospitals).
Yet no one can say for sure why. "We need to get behind the volumeoutcome relationship," said Diana Petitti, M.D., director of research and evaluation at Kaiser Permanente in Southern California. "We need to understand when high-volume hospitals have good outcomes, why, and transfer those practices to low-volume hospitals so that you have a level playing field."
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For cancer, the volumeoutcome relationship appears to be strongest among high-risk, infrequently performed operations, such as those for esophageal cancer and pancreatic cancer. For example, in a study published in 1998, Colin Begg, Ph.D., and his colleagues found that the mortality rate for patients undergoing esophagectomy at high-volume hospitals was 3%, compared with 17% at low-volume hospitals (see Stat Bite, p. 701). Similarly, the mortality rate for patients undergoing pancreatectomy at high-volume hospitals was 6%, compared with 13% at low volume-hospitals.
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Researchers have also found that 5-year survival after breast cancer surgery is statistically significantly greater for patients operated on at a high-volume hospital than at a low-volume hospital. And in a study in the March 2003 issue of the Journal of the American College of Surgeons, researchers found that patients ages 65 and older with pancreatic, lung, or colon cancer could expect to live substantially longer if their cancer surgery was performed at a high-volume hospital.
"The evidence is overwhelming that hospitals that do more procedures have better results," said Begg, of the Memorial Sloan-Kettering Cancer Center in New York. But he pointed out that the magnitude of the benefit depends on the type of cancer, as the benefits to simpler, more commonly performed procedures, such as colon cancer surgery or lung cancer surgery, have been more modest.
In its 1999 report, Ensuring Quality Cancer Care, the National Cancer Policy Board recommended that patients undergoing complicated cancer procedures associated with higher mortality in lower-volume settings receive care at high-volume facilities. Examples of such procedures include esophagectomy, pancreatectomy, removal of pelvic organs, and complex chemotherapy regimens.
The recommendations ignited a discussion about how to implement policies to concentrate care into higher-volume settings (a concept known as regionalization), and in May 2000, the Institute of Medicine held a workshop to discuss the issues. The resulting report, Interpreting the VolumeOutcome Relationship in the Context of Cancer Care, concluded that the evidence was strong enough to recommend regionalization of two high-risk surgeriespancreatectomy and esophagectomy.
Unraveling the Phenomenon
However, the report acknowledged that "much remains to be known about the relationship between volume and outcomes in the context of cancer care." In fact, researchers are quick to point out that volume is often a measure of other hospital characteristics, such as surgeon experience or the availability of a support team.
In a study in the Feb. 1, 2003, issue of the Journal of Clinical Oncology, Mark S. Litwin, M.D., of the University of California at Los Angeles School of Medicine, and his colleagues found that, after adjusting for hospital volume, patients with prostate cancer who were operated on by high-volume surgeons had fewer complications and shorter hospital stays than patients operated on by low-volume surgeons.
"If in fact its the skill of the surgeon rather than the supportive care of the hospital, then focusing attention on the hospital may not be the appropriate thing to do," said Begg.
Differences in the processes of care (i.e., surgical techniques used) between high- and low-volume hospitals may also contribute to differences in outcome.
In this issue of the Journal, David Hodgson, M.D., of the Princess Margaret Hospital and the University of Toronto in Canada, and his colleagues examined the relationship between hospital volume and outcomes in patients undergoing surgery for rectal cancer. They found that the probability of undergoing permanent colostomy (a procedure associated with substantial impairment in quality of life) increased statistically significantly as hospital volume decreased. For instance, patients in the lowest volume group had a 7% increase in absolute risk of permanent colostomy compared with those in the highest volume group.
"It appears that theres something about the way the operations are being performed in the low-volume hospital that leads to a greater risk of a patient having a colostomy than if theyre seen in a high-volume hospital," Hodgson said in an interview. "To understand why patients in high-volume hospitals are less likely to have a colostomy, it would be important to dig deeper to see if high-volume hospitals had access to better preoperative imaging or to see if patients seen in high-volume hospitals had tumors that were higher up in the rectum and more amenable to surgery that didnt require colostomy."
In some cases, the observed benefit for patients at high-volume hospitals may be the result of referral biases. For instance, if patients seen at high-volume hospitals are healthier than those seen at low-volume hospitals, this could explain the better outcomes.
But perhaps there is an even simpler explanation for the volumeoutcome phenomenon: "There are some who might argue that its not necessarily the case that the outcomes are good because the volumes are high but rather the volumes are high because the outcomes are good," said Hodgson.
Leveling the Playing Field
Certainly more work needs to be done, but some researchers maintain that the evidence for high-volume hospitals is too compelling to ignore. "The time for action is now," said Bruce Hillner, M.D., professor of medicine at the Massey Cancer Center of the Virginia Commonwealth University in Richmond. "How many more times do we need to see the same result before we begin to make a change?"
He pointed out that if similar benefits were seen with a new chemotherapy drug, "we would be jumping all over the map to get this new chemotherapy." He said that the simplest solution would be to concentrate cancer care in high- and medium-volume hospitals, pointing out that countries such as Canada, France, and Switzerland regionalize their cancer care.
Critics of regionalization have argued that shifting patients away from low-volume hospitals would overburden high-volume hospitals. But Hillner pointed out that most of the shift would occur between the low-and moderate-volume centers, where the difference in survival is most dramatic.
And to those who argue that the shift would leave low-volume hospitals ill-prepared to deal with emergencies, Hillner pointed out that cancer operations are rarely ever emergency procedures, and that patients have time to consider their options.
One effort to regionalize cancer care comes from the Leapfrog Group, a Washington, D.C.-based coalition of large employers. Leapfrog has set volume standards for several high-risk surgical procedures, including esophagectomy and pancreatectomy, and participating employers can use various incentives to encourage their employees to seek care in hospitals that meet these standards.
In a study in the September 2001 issue of Surgery, John Birkmeyer, M.D., of the Dartmouth-Hitchcock Medical Center in Lebanon, N.H., and his colleagues estimated that nationwide implementation of the Leapfrog standards would prevent 2,581 deaths, including 168 deaths of patients undergoing esophagectomy. "In the absence of better information about quality, theres no doubt that patients can improve their odds by picking a high-volume hospital," Birkmeyer said in an interview with the Journal.
Kaiser Permanentes Petitti agreed, but cautioned against making generalizations of the data. She pointed out that many low-volume hospitals have good outcomes. What consumers really need to know is how well hospitals do rather than the number of operations they performed, she said.
Leapfrog is hoping to do just that. "Our hope was that by using volume as a proxy measure, we would see more movement among healthcare providers in terms of their willingness to report more outcomes-oriented information," said Suzanne Delbanco, Ph.D., executive director of the Leapfrog Group, adding that the initiative has encouraged some hospitals to make data on patient mortality publicly available.
Other researchers suggest that the outcomes of individual surgeons may be influenced by providing information on performance to the surgeons. "Surgeons who have inferior outcomes may not realize that they are worse than average," said Begg.
He suggested creating feedback systems where surgeons could compare their outcomes with averages of surgeons performing similar surgeries. That way, surgeons with below-average outcomes may be motivated to find ways to improve their techniques.
Thomas Smith, M.D., a professor of medicine and health administration at the Massey Cancer Center of the Virginia Commonwealth University, offered another solution: Have hospitals and providers standardize their care by using a written protocol for all the procedures that need to take place before and during an operation.
"If all thats planned out, I would bet that would solve some of the problems," he said.
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