從改變生活方式做起 有7成機率可預防癌症

Americans seem very afraid of cancer, with good reason. Unlike other things that kill us, it often seems to come out of nowhere.

美國人似乎非常懼怕癌症，而且有着充分的理由。跟其他那些殺死我們的東西不一樣，癌症彷彿總是從天而降。

But evidence has increasingly accumulated that cancer may be preventable, too. Unfortunately, this has inflamed as much as it has assuaged people’s fears.

不過，有越來越多的證據表明，癌症或許也可以預防。不幸的是，這一發現引發的恐懼，和它驅除的一樣多。

As a physician, I have encountered many people who believe that heart disease, which is the single biggest cause of death aMong Americans, is largely controllable. After all, if people ate better, were physically active and stopped smoking, then lots of them would get better. This ignores the fact that people can’t change many risk factors of heart disease like age, race and family genetics.

作爲一名醫生，我遇到的很多人相信，美國人的單一最大死因——心臟病——在很大程度上是可控的。畢竟，如果吃得更健康，多做運動，並停止吸菸，大多數心臟病人的情況會好轉。但一個事實被忽略了，人們無法改變誘發心臟病的許多風險因素，比如年齡、種族和家族基因。

People don’t often seem to feel the same way about cancer. They think it’s out of their control. A study published in Science in January 2015 seemed to support that view. It tried to explain why some tissues lead to cancer more often than others. It found a strong correlation between the number of times a cell divides in the course of a lifetime and the risk of developing cancer.

對於癌症，人們似乎往往並不這樣看，而是認爲自己無法控制它。一項於2015年1月發表在《科學》雜誌(Science)上的研究，似乎爲這種觀點提供了支撐。它試圖解釋，爲什麼相比之下，某些組織更容易發展出癌症。文中發現，細胞在一生當中的分裂次數與罹患癌症的風險之間存在很強的相關性。

In other words, this study argued that the more times DNA replicates, the more often something can go wrong. Some took this to mean that cancer is much more because of “bad luck” than because of other factors that people could control.

換句話說，該研究認爲，DNA複製次數越多，出問題的可能性就越大。有人據此認爲，帶來癌症的主要是“壞運氣”，遠超其他一些人爲可控的因素。

Unfortunately, this simple explanation is not really what the study showed. Lung cells, for instance, divide quite rarely, and still account for a significant amount of cancer. Cells in the gastrointestinal tract divide all the time and account for many fewer cancers. Some cancers, like melanoma, were found to be in the group of cancers influenced more by intrinsic factors (or those we can’t control), when we clearly know that extrinsic factors, like sun exposure, are a major cause.

不幸的是，這個簡單的解釋並非該研究真正表明的東西。舉例來說，肺部細胞很少分裂，但肺癌在癌症中佔有很大的比重。胃腸道的細胞時時都在分裂，那裏生癌的機率卻要小得多。有些癌症，比如黑色素瘤，被發現屬於受內在因素影響更大的一類癌症（也就是我們無法控制的那種）；與此同時我們也清楚地知道，一些外在因素，比如陽光暴曬，是它的一大誘因。

Further, this study was focused more on the relative risks of cancer in one type of tissue versus another. What we really care about is how much we can reduce our own risk of cancer by changing our behavior.

此外，該研究更爲關注的是，一類組織與另一類組織相比，生癌的相對風險有多大。而我們真正關心的是，通過改變自己的行爲，我們可以在多大程度上降低罹患癌症的風險。

A more recent study published in Nature argues that there is a lot we can do. Many studies have shown that environmental risk factors and exposures contribute greatly to many cancers. Diet is related to colorectal cancer. Alcohol and tobacco are related to esophageal cancer. HPV is related to cervical cancer, and hepatitis C is related to liver cancer.

發表在《自然》雜誌(Nature)上的一項更爲近期的研究稱，我們能做的事其實很多。許多研究表明，環境風險因素及風險暴露會大大促進許多種癌症的發生。節食與大腸癌有關。酒精和菸草與食道癌有關。人乳頭瘤病毒(HPV)與宮頸癌有關。丙型肝炎與肝癌有關。

And you’d have to be living under a rock not to know that smoking causes lung cancer and that too much sun can lead to skin cancer.

只要不是與世隔絕的人應該都知道，吸菸會導致肺癌，日曬過多可能會導致皮膚癌。

Using sophisticated modeling techniques, the researchers argued that less than 30 percent of the lifetime risk of getting many common cancers was because of intrinsic risk factors, or the “bad luck.” The rest were things you can change.

通過使用精密的建模技術，研究人員提出，罹患癌症的終生風險有不到30%由內在因素導致，或說“壞運氣”。其他的都屬於你可以改變的東西。

Most recently, in JAMA Oncology, researchers sought to quantify how a healthful lifestyle might actually alter the risk of cancer. They identified four domains that are often noted to be related to disease prevention: smoking, drinking, obesity and exercise.

最近，在《美國醫學會期刊·腫瘤學》(JAMA Oncology)上發表的論文顯示，研究者試圖量化健康的生活方式可以如何實質性地改變罹患癌症的風險。他們找出了四個經常被指出與疾病預防有關的因素：抽菸、喝酒、肥胖和運動。

They defined people who engaged in healthy levels of all of these activities as a “low risk” group. Then they compared their risk of getting cancer with people who weren’t in this group. They included two groups of people who have been followed and studied a long time, the Nurses’ Health study and the Health Professionals Follow-up study, as well as national cancer statistics.

他們把在這四個方面保持健康水平的人列爲“低風險”人羣，然後把他們患癌症的風險與不在此列的人作比較。其中包括被追蹤和研究了很長時間的兩組人，即護士健康研究(Nurses’ Health study)和醫藥衛生從業人員隨訪研究(Health Professionals Follow-up study)的參與者，還參考了全美的癌症數據。

Of the nearly 90,000 women and more than 46,000 men, 16,531 women and 11,731 men fell into the low-risk group. For each type of cancer, researchers calculated a population-attributable risk, which is the percentage of people who develop cancer who might have avoided it had they adopted low-risk behaviors.

總共有將近9萬名女性和逾4.6萬名男性參與者，其中16531名女性和11731名男性屬於低風險人羣。研究人員計算了每種癌症的人羣歸因風險——即當初如果採取低風險行爲模式，或許本可以避免患上癌症的病人的比例。

About 82 percent of women and 78 percent of men who got lung cancer might have prevented it through healthy behaviors. About 29 percent of women and 20 percent of men might have prevented colon and rectal cancer. About 30 percent of both might have prevented pancreatic cancer. Breast cancer was much less preventable: 4 percent.

當初如果秉承健康的生活方式，大約82%的女性肺癌病人和78%的男性肺癌病人或許可以避免患上這種疾病。大約29%的女性和20%的男性或許本可以避免罹患結直腸癌。大約30%的男性和30%的女性或許本可以避免罹患胰腺癌。原本或許可以避免患上乳腺癌的病人比例要低得多，只有4%。

Over all, though, about 25 percent of cancer in women and 33 percent in men was potentially preventable. Close to half of all cancer deaths might be prevented as well.

不過，總體而言，大約25%的女性癌症病人和大約33%的男性癌症病人或許本可以把癌症拒之門外。此外，所有死於癌症的人中，大約有一半或許本可以避免這種結局。

No study is perfect, and this is no exception. These cohorts are overwhelmingly white and consist of health professionals, who are not necessarily like the population at large. But the checks against the national data showed that if anything, these results might be underestimating how much cancer is preventable by healthy behaviors.

沒有哪項研究是完美的，該研究也不例外。這些參與者均爲醫護專業人員，而且大多數都是白人，這和人口的整體結構有所不同。但與全國數據比對顯示，如果這有什麼影響的話，那就是：上述結論或許低估了通過採取健康的行爲模式預防癌症的成功率。

As we talk about cancer “moonshots” that will most likely cost billions of dollars and might not achieve results, it’s worth considering that — as in many cases — prevention is not only the cheapest course, but also the most effective.

我們在談論癌症“登月計劃”這一極有何能耗費數十億美元資金，但卻可能一無所獲的項目之際，有必要考慮一下——在許多情況下——預防不僅僅是最便宜的解決方案，而且是最有效的。

Simple changes to people’s behaviors have the potential to make sure many cancers never occur. They have a side benefit of preventing health problems in many other areas, too. Investment in these efforts may not be as exciting, but it may yield greater results.

人們只要改變自己的行爲方式，就有可能永遠把癌症拒之門外。這樣做還有附帶的好處：可以讓其他許多領域的健康問題得到預防。對這些預防工作的投資或許沒有那麼令人振奮，但卻可能帶來更大的回報。