長期アスピリン服用で結腸直腸ガンのリスクが低下する

画像 ポリプ発生の履歴がある1,100人以上の参加者は、結腸直腸癌発症の大きな危険があると考えられた。1994年と1998年の間に参加した後に、規則的に81ミリグラムまたは325ミリグラムのアスピリンまたはプラセーボのどちらかを服用し、すべては3年の間追跡された。その結果:低容量アスピリンは、結腸直腸ポリプ発症リスクを減らした。
 再度の大腸内視鏡検査を受けるまで平均4年間、850人を追跡続けた。
 週に4回以上低容量アスピリンを服用した人は、週2回以下のNSAIDs服用者に比べて13%(27%:40%)前癌状態の大腸直腸腺腫の発症率が低かった。
 アスピリンは多くの利点があり、心臓発作の既往がある場合は服用によりリスクの軽減が得られるが、消化管出血や潰瘍を起こす副作用がある。ハイリスクの患者が内視鏡の代わりアスピリンのようなNSAIDsにを服用することは勧められない。
 81mg~325mgの規則的な服用で前癌病変の発現を7%低下させ、全くNSAIDsを服用しない人に比較して相対的にリスクが28%低下していた。
-----------------------------------------------------------
Long-Term Aspirin Use Seems to Protect Against Colorectal Lesions
The benefit lasts even if you stop taking the drug, study finds
By Alan Mozes, HealthDay Reporter
http://health.msn.com/health-topics/colon-cancer/articlepage.aspx?cp-documentid=100232831

The benefit lasts even if you stop taking the drug, study finds.

TUESDAY, Feb. 10 (HealthDay News) -- Prolonged use of low-dose aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) appears to reduce the risk of precancerous lesions that can lead to colorectal cancer.

That's the conclusion of a new study of people at high risk for the disease.

"It's increasingly clear, and arguably proven, that NSAID drugs do interfere with the development of cancer in the large bowel," said study co-author Dr. John A Baron, a professor of both medicine and community and family medicine at Dartmouth Medical School.

"And this study," he added, "is a building block in our understanding of all that because it shows two things: One, if you take the NSAID drug for a while and then stop, you won't get a big rebound in terms of adenoma tumor risk. And two, if you don't stop taking an NSAID, but instead continue its use over time, the protective benefit will continue."

Baron and his colleagues presented their findings in the Feb. 18 issue of the Journal of the National Cancer Institute.

For the study, the researchers focused on people who had embarked on the long-term use of aspirin as part of the Aspirin/Folate Polyp Prevention Study. The more than 1,100 participants were considered at high risk for developing colorectal cancer because of a history of polyp development. After enrolling between 1994 and 1998, all were tracked for three years while regularly taking either 81 milligrams or 325 milligrams of aspirin, or a placebo.

The result: The low-dose aspirin reduced the risk of developing colorectal polyps.

Baron and his colleagues then continued to track 850 of the patients for an average of four years, until each underwent a follow-up colonoscopy. During this time, aspirin use was monitored and classified as either "sporadic" (less than two days a week), "moderate" (two to four days a week), or "frequent" (more than four days a week).

Patients who'd initially been assigned to low-dose aspirin in the first trial and continued to take the drug on a "frequent" basis had a 13 percent lower risk for developing precancerous lesions (known as colorectal adenomas), compared with those who had initially taken a placebo and then went on to use NSAIDs "sporadically." The risk difference between the two groups was approximately 27 percent versus 40 percent, the study found.

The researchers also saw a similar risk spread between "sporadic" and "frequent" users of higher-dose (325 mg) aspirin, but they said the difference did not appear statistically significant.

The researchers also noted that the protective benefit of aspirin for a few years appeared to continue for some time among those who stopped taking the drug.

Baron cautioned, however, that NSAID drugs such as aspirin should be taken advisedly because of the gastro-intestinal side effects.

"It's a genuine concern. And that leads to the issue that for any drug or any intervention, you have to consider all the possible outcomes, good and bad, that may ensue," he said.

"Aspirin, for example, has a lot of benefits," Baron added. "It reduces the risk for cardiovascular disease, certainly among people who have had a history of previous stroke or heart attack. But aspirin, like all the NSAIDs, has the problem of prompting GI bleeding and GI heartburn, and also infrequently ulcers.

But Dr. Jerald D. Wishner, director of colon and rectal surgery at Northern Westchester Hospital Center in Mount Kisco, N.Y., said high-risk patients shouldn't turn to NSAIDs instead of routine screenings, such as a colonoscopy.

"I think it is appropriate to recommend NSAIDs to our patients, because if I can reduce the risk by 10 to 15 percent, and all it involves is taking an aspirin a day, who wouldn't sign up for that?" he said. "But we're talking about a high-risk group here. So, at the same time, we have to advise these patients that they are still at a higher risk and recommend that they continue to come in for follow-up screenings as they would if they weren't talking the aspirin."

In related findings published in the same issue of the journal, an international team of researchers reported that regular aspirin use at doses ranging from 81 milligrams to 325 mg appeared to collectively lower the absolute risk for developing any kind of precancerous colorectal lesion by almost 7 percent. And in relative terms -- when compared with taking no NSAIDs at all -- those patients taking aspirin achieved a 28 percent reduction in their risk for developing advanced lesions.

More information

For more on colorectal cancer, visit the U.S. National Cancer Institute.
SOURCES: John Baron, M.D., professor of medicine, and professor of community and family medicine, Dartmouth Medical School, Lebanon, N.H.; Jerald D. Wishner, M.D., director of colon and rectal surgery, Northern Westchester Hospital Center, Mount Kisco, N.Y.; Feb. 18, 2009, Journal of the National Cancer Institute

Copyright © 2009 ScoutNews, LLC. All rights reserved.

-------------------------------------------------------
Journal of the National Cancer Institute Advance Access published online on February 10, 2009
JNCI Journal of the National Cancer Institute, doi:10.1093/jnci/djn485
© The Author 2009. Published by Oxford University Press.
ARTICLES

Aspirin for the Chemoprevention of Colorectal Adenomas: Meta-analysis of the Randomized Trials
Bernard F. Cole, Richard F. Logan, Susan Halabi, Robert Benamouzig, Robert S. Sandler, Matthew J. Grainge, Stanislas Chaussade, John A. Baron

Affiliations of authors: Department of Mathematics and Statistics, University of Vermont, Burlington, VT (BFC); Department of Epidemiology and Public Health, Queens Medical Centre, University of Nottingham, Nottingham, UK (RFL, MJG); Department of Biostatistics and Bioinformatics and the Cancer and Leukemia Group B Statistical Center, Duke University Medical Center, Durahm, NC (SH); Department of Gastroenterology, Hopital Avicenne, Bobigny, France (RB); Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, NC (RSS); Department of Gastroenterology, Hopital Cochin–Université René Descartes, Paris, France (SC); Department of Community and Family Medicine (BFC, JAB) and Department of Medicine (JAB), Dartmouth Medical School, Hanover, NH

Correspondence to: Bernard F. Cole, PhD, Department of Mathematics and Statistics, University of Vermont, 16 Colchester Ave, Burlington, VT 05401 (e-mail: ccole@cems.uvm.edu).

Background: Multiple lines of evidence indicate that aspirin has an antineoplastic effect in the large bowel. Randomized clinical trials have been conducted to evaluate the effectiveness of aspirin for reducing the risk of colorectal adenomas. A meta-analysis of these trials will provide more precise estimates of the aspirin effect, both overall and in subgroups.

Methods: We combined data from all randomized double-blind placebo-controlled trials that evaluated aspirin for the prevention of colorectal adenomas. We used random-effects meta-analysis to estimate risk ratios and 95% confidence intervals (CIs) for the effect of aspirin on the occurrence of adenomas and of advanced lesions (ie, tubulovillous adenomas, villous adenomas, adenomas ≥1 cm in diameter, adenomas with high-grade dysplasia, or invasive cancer). All statistical tests were two-sided.

Results: We identified four clinical trials with 2967 randomly assigned participants. Each trial evaluated aspirin for the secondary prevention of colorectal adenomas. Doses of aspirin tested ranged from 81 to 325 mg/d. The average age of participants at baseline was 58 years, and 60% were male. Median follow-up was 33 months. A total of 2698 participants underwent colonoscopic follow-up and were included in the analysis of adenoma occurrence and advanced-lesion occurrence after randomization. Among these participants, adenomas were found in 424 (37%) of the 1156 participants allocated to placebo and in 507 (33%) of the 1542 participants allocated to any dose of aspirin. Advanced lesions were found in 12% of participants in the placebo group and in 9% of participants allocated to any dose of aspirin. The pooled risk ratio of any adenoma for any dose of aspirin vs placebo was 0.83 (95% CI = 0.72 to 0.96). This corresponded to an absolute risk reduction of 6.7% (95% CI = 3.2% to 10.2%). For any advanced lesion, the pooled risk ratio was 0.72 (95% CI = 0.57 to 0.90). We found no statistically significant effect modification for any of the baseline factors studied.

Conclusion: Aspirin is effective for the prevention of colorectal adenomas in individuals with a history of these lesions.

この記事へのコメント

この記事へのトラックバック