“This is a very important study – the first study to show a legacy effect, with reduced mortality and a gain of 5 event-free years over 20 years attributable to a 5-year treatment allocation,” said discussant Harvey White of Auckland (New Zealand) City Hospital.
This legacy effect, he added, can be viewed as an ongoing carryover effect related to statin-induced slowing and/or stabilization of existing coronary artery plaque. The mechanism is unknown, Dr. White said, but the key to why the legacy effect was seen in WOSCOPS despite the use of pravastatin – a less potent statin – but not to date in other statin trials may lie in the fact that WOSCOPS was a primary prevention study and its participants had the youngest mean age of all the major statin trials.
“Their plaques may not have been calcified yet and therefore were more able to be modified and stabilized. If you treat very early you might get a bigger effect,” said to Dr. White.
Undercutting that argument, however, was the WOSCOPS finding that the long-term benefits of 5 years of pravastatin were independent of age at treatment, Dr. Packard said.
He believes based upon other studies that statins’ coronary disease prevention benefits are expressed within the first 12 months after starting therapy.
“It suggests that whatever is happening to the pathobiology of atherosclerosis happens within a year, and somehow a statis is introduced into plaque. That’s my guess, that an unstable plaque is reduced to a stable one. People then form a new trajectory going forward and they never catch up. We should think of atherosclerosis as a rate effect rather than something that either happens or doesn’t happen. It’s a rate of happening,” Dr. Packard asserted.
Asked why in the aftermath of the strongly positive 5-year results of WOSCOPS only 31% of patients in each treatment arm were on long-term statin therapy, he replied that 20 years ago in Scotland there really was no push for primary prevention.
“The 4S trial had come out the year before [Lancet 1994;344:1383-9] and placed the focus on secondary prevention. Statins were relatively expensive and everybody was putting their money into secondary prevention. Our health care system, which is socialized, had not put any emphasis at all on primary prevention. We were actually amazed that even 31% got treated,” the physician explained.
Dr. Packard reported serving as a consultant to Merck, Roche, and AstraZeneca.