倫敦大學瑪麗皇後學院（Queen Mary University of London）的最新研究發現，服用阿司匹林能夠極大減少患上並死於消化係統主要癌症（即腸、胃和食管癌症）的風險。

針對諸多評估預防性應用阿司匹林利弊的研究和臨床試驗，科學家首次對所有可用證據進行了審查。頂尖癌症期刊Annals of Oncology今日公布了一項研究結論。

在倫敦大學瑪麗皇後學院（Queen Mary University of London，位於英國倫敦）的癌症預防中心負責人Jack Cuzick教授的帶領下，該研究團隊發現服用十年阿司匹林可以降低腸癌發病率約35%，降低腸癌死亡率40%。食管癌和胃癌的患病率下降了30%，死亡率也降低了35-50%。

要獲得阿司匹林帶來的好處，證據顯示50-65歲人群必須每日服用75-100毫克的阿司匹林，堅持至少5年以上或許10年以上。服用阿司匹林的前三年不會出現效果，隻有在服用五年後才會降低死亡率。

然而，研究還警告，長期服用阿司匹林會增加消化係統出血（如胃出血）的風險。60歲人群每日服用阿司匹林，堅持十年，則消化係統出血的風險會增加2.2%-3.6%，這對很小一部分人群（少於5%）而言可能會危及生命。

整體而言，70歲以下人群發生嚴重或致命性胃腸道出血的幾率非常小，但是70歲以後該幾率會大大增加。服用阿司匹林的另一副作用體現在消化性潰瘍上，發生消化性潰瘍的幾率增加了30%-60%。

研究還發現無法確定將阿司匹林利弊比最大化的最適當服用劑量，不同的臨床試驗和研究采用的劑量區間為75毫克~325毫克。並且，服用阿司匹林超過十年是否會帶來更多好處，這一點尚不明確。

Jack Cuzick教授評論：“人們早就知道阿司匹林作為市場上最便宜、最常見的藥物之一，可以防止患上某些類型的癌症。但是在我們此次對所有可用證據進行分析研究之前，人們並不了解服用阿司匹林是否利大於弊。

“雖然有一些不容忽視的嚴重副作用，但是每日服用阿司匹林看起來是戒煙和減肥之外減少癌症患病率的最佳方案，並且可能更容易實施。”

“我們的研究顯示，50-65歲的人群每日服用阿司匹林，堅持至少十年，則癌症、中風和心髒病的發病率會降低,男性9%，女性7%。如果服用超過20年，以上疾病的整體死亡數也會降低大約4%。服用阿司匹林的好處在降低癌症死亡率方麵尤為明顯。

“出血的風險與許多已知因素有關，而人們需要在開始定期服用阿司匹林前了解這些因素。建議在開始每日服用前先谘詢醫師。”

我們還需要進一步研究，才能更加明確服用阿司匹林的最大受益人群以及麵臨出血副作用的高危人群。

原文標題：Estimates of benefits and harms of prophylactic use of aspirin in the general population
原文鏈接：http://annonc.oxfordjournals.org/content/early/2014/07/30/annonc.mdu225.full

作者：J. Cuzick1, M. A. Thorat1, C. Bosetti, P. H. Brown, J. Burn4, N. R. Cook, L. G. Ford, E. J. Jacobs, J. A. Jankowski, C. La Vecchia, M. Law, F. Meyskens, P. M. Rothwell, H. J. Senn, A. Umar

Abstract

Background Accumulating evidence supports an effect of aspirin in reducing overall cancer incidence and mortality in the general population. We reviewed current data and assessed the benefits and harms of prophylactic use of aspirin in the general population.

Methods The effect of aspirin for site-specific cancer incidence and mortality, cardiovascular events was collated from the most recent systematic reviews. Studies identified through systematic Medline search provided data regarding harmful effects of aspirin and baseline rates of harms like gastrointestinal bleeding and peptic ulcer.

Results The effects of aspirin on cancer are not apparent until at least 3 years after the start of use, and some benefits are sustained for several years after cessation in long-term users. No differences between low and standard doses of aspirin are observed, but there were no direct comparisons. Higher doses do not appear to confer additional benefit but increase toxicities. Excess bleeding is the most important harm associated with aspirin use, and its risk and fatality rate increases with age. For average-risk individuals aged 50–65 years taking aspirin for 10 years, there would be a relative reduction of between 7% (women) and 9% (men) in the number of cancer, myocardial infarction or stroke events over a 15-year period and an overall 4% relative reduction in all deaths over a 20-year period.

Conclusions Prophylactic aspirin use for a minimum of 5 years at doses between 75 and 325 mg/day appears to have favourable benefit–harm profile; longer use is likely to have greater benefits. Further research is needed to determine the optimum dose and duration of use, to identify individuals at increased risk of bleeding, and to test effectiveness of Helicobacter pylori screening–eradication before starting aspirin prophylaxis.