Researchers from Stanford University School of Medicine in Stanford, Calif., have pooled individual patient data from 10 different clinical trials to compare the effectiveness of CABG with the less-invasive PCI on specific groups of patients for the first time, according to a study published online March 19 in the Lancet.
Almost 8,000 subjects showed that for patients suffering from multi-vessel coronary artery disease (CAD) who have diabetes and for patients older than 65, CABG may be a better treatment choice than PCI, according to the researchers. In patients 55 years and younger, PCI may be the best choice.
"Whether you have diabetes really makes a big difference," said lead investigator Mark Hlatky, MD, professor of health research and policy and of cardiovascular medicine at Stanford. "Over several years there's a much lower rate of death with bypass surgery. The patient's age was the other major factor that affected outcomes, and this was a bit of a surprise."
The study showed that the benefits of one course of treatment for specific sets of patients with coronary heart disease over another, according to the researchers. For patients with diabetes, the mortality rate after a five-year follow-up was 12 percent for those who had bypass surgery compared with 20 percent for the angioplasty procedure. For patients older than 65, the mortality rate was 11 percent for those who had bypass compared with 15 percent for those who had angioplasty.
"Traditionally the goal of clinical research has been to determine if a particular treatment works better than a placebo. Relatively little research has been done to determine if one active treatment is better than another, Hlatky said.
Because of soaring rates of CAD, Americans now average nearly 250,000 bypass surgeries and more than 660,000 angioplasty procedures annually, totaling more than $100 billion in medical costs. With such high stakes, making informed decisions is a higher priority than ever, the researchers wrote.
In an accompanying editorial, David Taggart, MD, PhD, professor of cardiovascular surgery at the University of Oxford in England, referred to this study as "the most definitive and authoritative analyses" of randomized trials comparing bypass surgery to PCI. What is so significant, he wrote, is that this study was able to compare high number of patients by pooling research from 95 percent of available randomized trials.
"There was a first wave of studies in which PCI was done using just balloon angioplasty, and then a second wave of studies in which PCI was done using bare-metal stents," Hlatky said. "We now have long-term outcome data from these studies, which is what we need to provide a fair comparison of PCI with bypass surgery." The next generation of studies will include angioplasty done with drug-eluting stents, but none were included in this study because long-term follow-up is not yet available.
"It took some time to get individual patient data from all the participating trials, but it was worth it because the pooled analysis is much more valuable if it's based on essentially all the data. In the end we were able to analyze data from 95 percent of all the patients worldwide with multi-vessel coronary disease enrolled in a clinical trial of bypass surgery and angioplasty."
After the data were collected, the researchers then had to standardize the results to be able to compare "apples to apples," Hlatky said, due to various differences used in data collection methods.
In future studies, the researchers hope to analyze the new results from their study to help understand why bypass is more effective for treating diabetes patients and older patients.
"We're not really sure of why surgery was better for these groups of patients," Hlatky said. "It's a very important and provocative observation that needs to be investigated further."