DENVER (EGMN) — Asthma may be a risk factor for lung cancer, according to two new meta-analyses.

The public health implications of such an association would be enormous. Asthma affects at least 15 million Americans, 40% of them children. Its prevalence has been climbing steadily for decades in developed countries, more than doubling in the United States during a recent 20-year period. And lung cancer is the second most common noncutaneous malignancy in this country, with 10% of lung cancer deaths not attributable to smoking, Chanis Mercado said at the annual meeting of the American Public Health Association.

One of the two meta-analyses she performed as a Ph.D. candidate in public health at the Ponce (P.R.) School of Medicine involved 17 high-quality case-control studies with a total of 54,238 subjects. The conclusion was that individuals with asthma had 34% greater odds of having lung cancer, compared with matched controls without asthma.

A separate meta-analysis that included 16 high-quality cohort studies and 1,384,824 subjects showed that those with asthma were 46% more likely to develop lung cancer than were subjects without asthma.

These results were statistically robust. Eliminating any individual study didn’t substantially change the results. Tests for the existence of publication bias proved reassuringly negative.

One biologically plausible possible mechanism for the observed asthma–lung cancer link is that the persistent chronic inflammation that is a defining feature of asthma causes DNA damage to cells in the airway. Another possibility is that asthma patients have defective clearance of toxins in the bronchioalveolar epithelium, resulting in prolonged local exposure to carcinogens, she said.

The clinical implication of these two meta-analyses is that asthma patients ought to be screened earlier and more often for signs and symptoms of lung cancer, Ms. Mercado continued. This screening might take the form of chest x-rays, sputum cytology tests, and/or a low threshold for acting on symptoms of weight loss or hemoptysis.

Ms. Mercado declared having no relevant financial interests.

Copyright (c) 2010 Elsevier Global Medical News. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

丹佛(EGMN)——根据两项新的荟萃分析，哮喘可能是肺癌的一个危险因素。这种相关性有着极大的公共卫生意义。

至少有1,500万美国人罹患哮喘，其中40%是儿童。数十年来发达国家哮喘的发生率一直稳步上升，最近20年美国哮喘的发生率增加一倍以上。肺癌是美国的第二大常见非皮肤恶性肿瘤，10%的肺癌死亡与吸烟无关。为了明确哮喘与肺癌是否具有相关性，美国波多黎各大学医学院公共卫生在读哲学博士Chanis Mercado进行了两项荟萃分析。 

其中一项荟萃分析涉及17项高质量的病例对照研究，共54,238名受试者。结果揭示，哮喘个体发生肺癌的几率较与之匹配的非哮喘对照大34%。另外一项独立的荟萃分析纳入了16项高质量的队列研究，共1,384,824名受试者，其结果显示，哮喘患者发生肺癌的几率较非哮喘患者高46%。这些结果在统计学上均极具说服力。 

根据这两项荟萃分析的结果，临床上医生应该对哮喘患者进行更早、更频繁的筛查，及早发现肺癌的症状和体征。具体筛查项目包括胸部X线检查、痰液细胞学检查和(或)是否达到标志性的体重减轻或咯血症状的下限阈值。 

Mercado女士无相关的经济利益声明。

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