改變生活型態可預防50%的常見癌症


  【24drs.com】根據國際癌症控制聯盟(UICC)2012世界癌症研討會的報告,如果人們落實已知的癌症預防方法,超過50%的癌症是可以預防的。
  
  華盛頓大學醫學院的Graham Colditz博士報告指出,許多介入方式大多與生活型態有關,或者是高收入國家的高花費介入方法,若廣泛運用15-20年,可預防大部分的癌症。
  
  最主要的生活型態介入方式是戒菸。
  
  Colditz博士表示,高收入國家有三分之一的癌症肇因於抽菸,如果抽菸率可以降低到猶他州目前的比率[約11%],美國在10-20年內,抽菸相關癌症可降低75% — Colditz博士認為這是可行的目標,因為該國的抽菸率已經逐漸降低。
  
  同樣地,估計過重或肥胖引起當今約20%的癌症,如果人們可以維持健康身體質量指數(BMI),癌症發生率可在2-20年內降低約50%。(如同其他研究者所指,預防癌症之健康BMI值為21-23 kg/m2。)
  
  Colditz博士等人估計,飲食不佳及缺乏運動各與約5%的癌症有關,改善飲食可以降低癌症發生率約50%,增加體能活動可以在5-20年內降低癌症發生率達將近85%。
  
  根除主要癌症相關病毒的方法是針對3種病毒—人類乳突病毒和B型與C型肝炎病毒—廣泛執行嬰幼童免疫計畫,可在20-40年內獲致100%降低病毒相關癌症;之後,藉由高科技介入方式,至少在高收入國家,可預防主要的癌症和癌症相關死亡率,首要為乳癌。
  
  Colditz博士表示,我們已經發現,相較於安慰劑,tamoxifen在5年時降低了侵犯性和非侵犯性乳癌率達50%以上。
  
  同樣地,根據「Study of Tamoxifen and Raloxifene (STAR)」分析乳癌風險增加的停經婦女,raloxifene在5年時降低侵犯性乳癌風險達約50%,STAR研究婦女接受raloxifene者的子宮癌比對照組降低36%。
  
  Colditz博士解釋,我們也觀察到,婦女健康介入研究結果的乳癌發生率降低10%-15%顯然不是因為乳房攝影改變,而是移除乳癌的促發因子;在婦女健康介入研究之後,美國的荷爾蒙替代治療率驟降,顯示它和乳癌風險增加有關。
  
  帶有BRCA1或BRCA2基因的婦女雖罕見,進行雙側卵巢切除術和高風險婦女的乳癌風險降低50%有關;據估計,停經後體重降低(超過20磅[9公斤])在2-20年降低乳癌風險達50%。
  
  此外,Colditz博士指出,追蹤近20年顯示,阿斯匹靈與降低大腸癌死亡率40%有關,大腸直腸癌篩檢也同樣可降低死亡率(30%-40%)。
  
  實際上,最近一篇研究顯示,追蹤中位數11.9年之後,大腸直腸癌發生率相對風險降低21%,成人彎曲式乙狀結腸鏡篩檢且在3或5年時重複篩檢,死亡率比一般照護治療者降低26%(N Engl J Med. 2012;366:2345-2357)。
  
  Colditz博士指出,麻塞諸塞州在1997年開始協同一致的致力於促進大腸癌篩檢,從1997-2010年,適當年紀的居民在這段期間的乙狀結腸鏡或大腸鏡檢查率幾乎倍增,大腸癌的年齡標準化死亡率降低達35%。
  
  他指出,30年前,流行病學家指出菸酒和飲食—他們的定義是飲食總攝取量、缺乏運動和肥胖— 影響了半數以上的癌症。我們無法預期這些結果可以立即發生,但是它們對整個社會有極大助益。
  
  瑞士日內瓦國際癌症控制聯盟的David Hill博士表示,這絕對是癌症整體事務的核心,就像UICC,要確保我們的癌症知識被運用。
  
  Hill博士指出,我們未能有效運用所知的知識,我們的挑戰在於發展「落實科學」這項新科學,我們要致力於將發現的效益運用到全體人的健康助益。
  
  資料來源:http://www.24drs.com/professional/list/content.asp?x_idno=6936&x_classno=0&x_chkdelpoint=Y
  

Lifestyle Changes Could Prevent 50% of Common Cancers

By Pam Harrison
Medscape Medical News

September 5, 2012 (Montreal, Quebec) — More than 50% of cancer could be prevented if people simply implemented what is already known about cancer prevention, according to a researcher here at the Union for International Cancer Control (UICC) World Cancer Congress 2012.

Graham Colditz, PD, DrPH, from the Washington University School of Medicine in St. Louis, Missouri, reported that a number of interventions, largely involving lifestyle behaviors, but also involving higher-cost interventions in high-income countries, could prevent a large proportion of cancers in 15 to 20 years if widely applied.

Among the "biggest buys" from lifestyle intervention is smoking cessation.

"One third of cancer in high-income countries is caused by smoking," Dr. Colditz said. If smoking rates could be reduced to the current levels in Utah [about 11%], the United States could see a 75% reduction in smoking-related cancers in 10 to 20 years — a target that Dr. Colditz feels is feasible in countries where smoking rates have already declined considerably.

Similarly, it is estimated that being overweight or obese causes approximately 20% of cancer today. If people could maintain a healthy body mass index (BMI), the incidence of cancer could be reduced by approximately 50% in 2 to 20 years. (A healthy BMI for cancer prevention is from 21 to 23 kg/m2, as other speakers pointed out.)

Dr. Colditz, among others, estimates that poor diet and lack of exercise are each associated with about 5% of all cancers. Improvement in diet could reduce cancer incidence by 50% and increases in physical activity could reduce cancer incidence by as much as 85% in 5 to 20 years.

Eradicating the main viruses associated with cancer worldwide by implementing widespread infant and childhood immunization programs targeting 3 viruses — human papillomavirus and hepatitis B and C — could lead to a 100% reduction in viral-related cancer incidence in 20 to 40 years, he added. Then there are the "higher tech" interventions that, at least in high-income countries, could prevent a significant proportion of cancer and cancer-related mortality, starting with breast cancer.

"We have shown that tamoxifen reduces the rate of both invasive and noninvasive breast cancer by 50% or more, compared with placebo, at 5 years," Dr. Colditz said.

Similarly, raloxifene has been shown to reduce the risk for invasive breast cancer by about 50% at 5 years, according to the Study of Tamoxifen and Raloxifene (STAR) in postmenopausal women at increased risk for breast cancer. Women in STAR who received raloxifene also had 36% less uterine cancers than control subjects.

"We also observed a 10% to 15% decrease in breast cancer incidence following the results of the Women's Health Initiative that were clearly not due to changes in mammography, but rather to the removal of a late promoter [of breast cancer]," Dr. Colditz explained. The use of hormone replacement therapy in the United States plummeted after the Women's Health Initiative showed that it was associated with an increased risk for breast cancer.

And bilateral oophorectomy in women carrying the BRCA1 or BRCA2 gene, although rare, has been associated with a 50% reduction in breast cancer risk among high-risk women. It has also been estimated that weight loss after menopause (more than 20 lbs [9 kg]) reduces breast cancer risk by 50% in 2 to 20 years.

In addition, Dr. Colditz noted that approximately 20 years of follow-up has shown that aspirin is associated with a 40% reduction in mortality from colon cancer. Screening for colorectal cancer has a similar magnitude of mortality reduction (30% to 40%).

Indeed, a recent study showed that after a median follow-up of 11.9 years, there was a 21% relative risk reduction in the incidence of colorectal cancer and a 26% reduction in mortality in adults screened with flexible sigmoidoscopy, with a repeat screening at 3 or 5 years, compared with those treated with the usual care (N Engl J Med. 2012;366:2345-2357).

Dr. Colditz noted that a concerted and collective effort to promote colon cancer screening in Massachusetts was initiated in 1997. From 1997 to 2010, "we saw almost a doubling of screening with sigmoidoscopy or colonoscopy in age-eligible residents and, during that time, the age-standardized mortality from colon cancer went down by 35%," he said.

They could bring huge benefits to society.

He added that 30 years ago, "epidemiologists were already showing that tobacco, alcohol, and diet — which in their definition was the sum of dietary intake, lack of physical activity, and obesity — accounted for more than half of all cancer. We can't expect these changes in outcome to occur overnight, but they could bring huge benefits to society," he explained.

Session cochair David Hill, AO, PhD, MD (Hon), from the Union for International Cancer Control in Geneva, Switzerland, told Medscape Medical News that it is "absolutely core business" for global bodies in cancer, such as the UICC, to ensure that the knowledge we have about cancer is applied.

The challenge for us is to develop a new form of cancer science called 'implementation science.'

"We have far more knowledge at the moment than we are making use of effectively," Dr. Hill noted. "The challenge for us is to develop a new form of cancer science called 'implementation science.' We've got to work out how to take the benefits of discoveries to the people for population-wide health benefits."

Union for International Cancer Control (UICC) World Cancer Congress 2012. Presented August 29, 2012.

    
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