LONDON -- Only about half of the cancer drugs approved by the European Medicines Agency in the last few years were later shown to help patients live longer or improved their lives, a new study says.
Scientists in Britain and Latvia analyzed reports from the European regulator on cancer approvals from 2009 to 2013. Many of the approvals were based only on initial measures that suggested the drug might improve health, like tumor shrinkage.
During that time, the EMA green-lighted 48 drugs for 68 different uses. Of those, the researchers determined that 35 approvals significantly improved patient survival or their quality of life, while data for 33 uses were "uncertain."
Many regulators, including the U.S. Food and Drug Administration, often OK drugs based on initial surrogate measures because it can take many years before solid data about the drugs' effectiveness exists. In the study, 39 of the 68 approvals relied on surrogate measures.
"We were quite surprised about the high proportion of drugs entering the market without evidence," said Huseyin Naci, of the London School of Economics and Political Science, one of the study's authors.
The European Medicines Agency declined to comment on the research.
Naci said since regulatory agencies don't require drugmakers to prove that their treatments improve or extend life, there is little incentive for companies to produce more rigorous proof that they work. But in many European countries with universal health care, national health systems often have stricter ways of deciding what cancer treatments patients get, after experts weigh whether an extra few months of life are worth the often-toxic side effects and costs of the drugs.
Among the drugs that were shown to help patients were 23 cancer medicines including Herceptin, often used to treat breast cancer, and Zytiga for prostate cancer.
For other drugs, however, researchers often found that when they extended survival they were often "marginal."
The study was published online Thursday in the journal, BMJ.
The research "paint(s) a sobering picture," wrote Vinay Prasad, an assistant professor of medicine at the Oregon Health and Science University, in an accompanying editorial. He said most cancer drugs - which cost about $100,000 per year of treatment - are being approved based on "flimsy or untested" initial measures and declared that the regulatory system was "broken."
The researchers acknowledged several limitations in their study, including several cases in which the results were incomplete or ambiguous.
Rose Gray, a senior policy adviser at the British charity Cancer Research UK, said the trend toward personalized medicine in cancer could make gathering large amounts of data about drugs' effectiveness challenging, since these treatments often target small groups of patients with certain genetic traits.
But she said that even though many new drugs may only extend patients' lives a few weeks or months, such gains can be worthwhile.
"For cancer patients nearing the end of their lives, every day counts," Gray said.