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The Dangers of Secondhand Smoke
Most people know that cigarette smoking is harmful to their health. Scientific research shows that it causes many kinds of diseases. In fact， many people who smoke get lung cancel. However，Edward Gilson has lung cancer， and he has never smoked cigarettes. He lives with his wife， Evelyn，who has smoked about a pack of cigarettes a day throughout their marriage. 46______
No one knows for sure why Mr. Gilson has lung cancer. Nevertheless， doctors believe that secondhand smoke may cause lung cancer in people who do not smoke because nonsmokers often breathe in the smoke， from other people"s cigarettes. 47______ The US Environmental Protection Agency reports that about 53，000 people die in the United States each year as a result of exposure to secondhand smoke.
The smoke that comes from a lit cigarette contains many different poisonous chemicals. In the past， scientists did not think that these chemicals could harm a nonsmoker"s health. 48______ They discovered that even nonsmokers had unhealthy amounts of these toxic （有毒的 ） chemicals in their bodies. As a matter of fact， almost all of US breathe tobacco smoke at times， whether we realize it or not. For example， we cannot avoid secondhand smoke in restaurants， hotels and other public places. Even though many public places have nonsmoking areas， smoke flows in from the areas where smoking is permitted. It is even harder for children to avoid secondhand smoke.
49______ Research shows that children who are exposed to secondhand smoke are sick more often than children who live in homes where no one smokes and that the children of smokers are more than twice as likely to develop lung cancer when they are adults as are children of nonsmokers. The risk is even higher for children who live in homes where both parents smoke.
People are becoming very aware of the dangers of secondhand smoke. 50______
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Cancer Drug Trials Often Halted Early
An increasing number of clinical trials for new cancer treatments are being halted before the risks and benefits have been fully evaluated， say Italian researchers， who warn that this growing trend could put patients at risk of harm from new therapies rushed into use.
The researchers looked at 25 randomized， controlled clinical trials that were stopped early because the treatments had started to show benefit to patients.
"When we analyzed 25 trials over a 10-year period between 1997 and 2007， we found a consistent increase in prematurely stopped trials——more than 50 percent were stopped within the last three years，" study co-author Giovanni Apolone said at a news conference Tuesday.
Of 14 trials halted early and published between 2005 and 2007， the researchers found that 11（79 percent） of them were used to support drug approval applications submitted to the European Medicines Agency and the U.S. Food and Drug Administration.
"This suggests a strong commercial component in stopping trials prematurely. In fact， this strategy could guarantee quicker access to the market for companies. On the other hand， a quicker clinical drug development may lead to an "immature" benefit/risk balance of new drugs，"Apolone said.
He and his colleagues "are aware that trials stopped early because they are showing benefit may result in identification of promising new treatments for patients. However， findings obtained following this strategy should be considered to be preliminary results that require subsequent confmnation."
It can take several years for the long-term benefits or harmful side effects of a new treatment to become apparent， Apolone noted， but the average duration （持续时间） of the 25 studies he and his colleagues analyzed was 30 months， with a range from 12 to 64 months.
They also found that at the time five of the studies were stopped， they"d enrolled less than 40 percent of the total number of patients planned for final analysis.
"Clinical trials need to stop early for superior benefit whenever there"s proof beyond reasonable doubt that the new treatment really is superior. That would be an ethical obligation，"Stuart Pocock， a professor of medical statistics at the London School of Hygiene and Tropical Medicine in the United Kingdom， said at the news conference. "However， too many trials are stopped early claiming efficacy （功效） without strong evidence being available."
The number of prematurely stopped clinical trials has increased recently. 查看材料
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