各地甲狀腺癌流行事出有因

Historically, the science of epidemiology was directed toward identifying and controlling epidemics of infectious disease. In a study just published in the New England Journal of Medicine, my colleagues and I highlight another important job for epidemiologists: identifying and controlling epidemics of medical care.

歷史上，流行病學的研究方向是確診和控制廣泛傳播的傳染病。我和同事們在《新英格蘭醫學雜誌》(New England Journal of Medicine)上剛剛發表的一篇研究論文中指出，流行病專家還有另外一項任務：識別和控制醫療界造成的流行病。

The setting is South Korea, where, over the last two decades, the incidence of thyroid cancer has increased fifteenfold. Nowhere in the world is the rate of any cancer growing faster.

研究的背景是韓國。在過去20年裏，這裏甲狀腺癌的發病率提高到了最初的15倍。全世界任何地方都沒有哪種癌症能如此之快地增長。

We’ve all been taught to seek biological explanations for a significant rise in disease — perhaps a new infectious agent or environmental exposure. But in South Korea, we are seeing something different: an epidemic of diagnosis.

我們受過的教育都是，爲發病率的顯著提高尋找生物學上的解釋，或許是新的病原體，或許是環境暴露。然而在韓國，我們看到了不同的情況，這種流行病是因爲診斷造成的。

In 1999 the government initiated a national health-screening program focused on reducing cancer and other common diseases. Although thyroid cancer screening was not included in the program, all it requires is a simple test — an ultrasound of the neck. Hospitals have ultrasound machines and so do many doctors’ offices. Both promoted thyroid cancer screening as an inexpensive add-on to the government program. It was an easy sell, particularly with the government, the medical community, the news media and cancer “survivors” praising the virtue of early cancer detection.

1999年，韓國政府啓動了一項全國性的體檢計劃，主要目的是減少癌症和常見病。儘管其中並不包括甲狀腺癌篩查，但它只需要一個簡單的步驟：頸部超聲波檢查。醫院裏有超聲波設備，很多醫生的診所裏也有。醫院和醫生都認爲，它是政府計劃之外一項廉價的補充檢查，因而鼓勵患者檢查。而患者也很樂於接受，尤其是因爲政府、醫療界、新聞媒體和癌症“生還者”都稱讚，及早發現癌症有好處。

In doing so they inadvertently highlighted the major harm of early detection: What was a rare cancer is now the most common cancer in South Korea.

但這樣做也意外地突顯了及早診斷的巨大危害：一種本來罕見的癌症，成爲了韓國最常見的癌症。

Where did all those new thyroid cancers come from? They were always there. As early as 1947 pathologists recognized that, although it was a very rare cause of death, thyroid cancer was a frequent finding during autopsies. Studies have since shown that over a third of adults have thyroid cancer. Virtually all of these cancers are small “papillary thyroid cancers,” many of which will never become evident during a person’s life.

那些新增的甲狀腺癌患者是從哪裏來的呢？他們其實一直存在。早在1947年，病理學家就發現，儘管極少成爲死因，但是在屍檢中經常發現死者患有甲狀腺癌的情況。從那時起，研究就發現，超過三分之一的成年人患有甲狀腺癌。其中幾乎所有人患的都是微小的“甲狀腺乳頭狀癌”，許多人一生中症狀都不明顯。

Unless that person receives a screening ultrasound. In fact, virtually all the newly identified thyroid cancers in Korea are papillary thyroid cancers. How do we know this is not a real epidemic of disease? Because the number of Koreans dying from thyroid cancer has not changed. If the screening were saving lives, the death rate would decline, or increase more slowly as the epidemic spread — but not stay perfectly flat.

除非這個人接受了超聲波檢查。事實上在韓國，幾乎所有新確診的甲狀腺癌都是乳頭狀癌。我們怎麼才能知道這不是真正的流行病呢？因爲在韓國，死於甲狀腺癌的人數並沒有變化。如果超聲檢查挽救了患者的生命，那麼死亡率應該降低纔對，而如果流行病蔓延開來，死亡率應該緩慢上升纔對——然而數據卻完全沒有起伏。

An epidemic of diagnosis is not good for anyone’s health. Resources are needlessly diverted; people are needlessly scared. But the biggest problem is that it begets an epidemic of treatment.

診斷呈現的流行病對任何人的健康都沒有好處，而且它毫無必要地轉移了資源，也毫無必要地驚嚇了患者。然而最大的問題是，它在醫療體系內催生了過度治療。

The majority of patients given diagnoses of thyroid cancer have their thyroid gland removed. The thyroid is an important gland — it produces the hormones that control metabolism. Without it, patients may need lifelong thyroid replacement therapy. And it can take doctors a while to find the right dose for each individual. In the meantime, patients suffer from the effects of too little or too much thyroid hormone, including energy and weight fluctuations.

多數被診斷患有甲狀腺癌的患者，被切除了甲狀腺。然而甲狀腺是一個重要的腺體，它能分泌控制新陳代謝的激素。如果切除了，患者就可能會終生需要甲狀腺替代治療，而且醫生可能需要一段時間才能爲每一位患者找到恰當的劑量。與此同時，患者還要承受甲狀腺素水平過低或過高的後果，包括精力和體重的波動。

The surgery has other less common complications. In South Korea and the United States about 10 percent of patients have problems with calcium metabolism and about 2 percent experience vocal cord paralysis. And, as with any surgery, there can be life-threatening effects — blood clots in the lungs, heart attacks and strokes. In about two of every 1,000 thyroid cancer operations, the patient dies. It’s rare, but it happens.

這種手術也會產生一些並不十分常見的併發症。在韓國和美國，大約10%的患者產生了鈣質代謝問題，約有2%的患者發生了聲帶麻痹。此外，就像任何一種手術一樣，它可能會產生威脅生命的後果，如肺部血凝塊、心肌梗死和中風。每一千例甲狀腺癌手術中，大約會有兩名患者身亡。很罕見，但的確會發生。

Could what happened in South Korea happen here? Absolutely. Even without a concerted effort to promote screening, thyroid cancer incidence in the United States is up threefold since 1975. To reverse this trend, we need to actively discourage early thyroid cancer detection.

在韓國發生的情況也會在美國發生嗎？絕對會。儘管沒有各方同心協力推動篩查，美國的甲狀腺病例自1975年以來也已經提高到了最初的三倍。要想扭轉這種趨勢，我們需要積極地勸阻甲狀腺癌的早期檢查。

The virtue of early detection is so ingrained and so appealing that many assume that screening can only be good for you. But that’s not true. The Korean experience illustrates the downside of trying to find cancer early: overdiagnosis and overtreatment. The problem is greatest for thyroid and prostate cancer, but also exists for cancers of the lung, breast, skin and kidney. And then there is all the angst surrounding screening — that can’t be good for anyone’s health.

及早檢查有好處的觀念根深蒂固，而且也很吸引人，所以許多人都認爲，做一下檢查只會有好處。然而事實並非如此。韓國的經驗顯示出，試圖早期診斷癌症的做法有負面的影響：過度診斷和過度治療。甲狀腺癌和前列腺癌的問題最爲嚴重，然而對肺癌、乳腺癌、皮膚癌、腎癌也存在。當然還有對於檢查的焦躁，這可是對任何人的健康都不會有好處的。

Of course, screening makes sense in some situations: in particular for people who are at a genuinely high risk for the cancer — those with multiple cancer deaths in their family history. People at average risk who expect to live long enough to experience the potential benefit in the future — and who are willing to accept the chance of harm from unneeded treatment now — may also decide that the screening makes sense for them.

當然，檢查在一些情況下是有意義的，尤其是癌症真正的高危患者：家族內有多人死於癌症的患者。患病風險中等，但預期壽命足夠長，未來可以體驗到潛在收益的人——以及那些願意接受現在並不需要的治療帶來的受到損害的可能性的人——或許也會認定接受檢查是合理的。

Nevertheless, those interested in early detection may want to concern themselves with the question of how early. Sure, we would rather diagnose cancer in a small breast lump than wait until it develops into a large breast mass. But it may be excessive to extrapolate from that to searching for microscopic cancers. Many of the thyroid cancers found in South Korea were less than a centimeter in size. If we look for earlier cancers, we will always find more. And, at some point, we identify too many things that are better off left unfound. In short, having doctors not look too hard for early cancer is in your interest.

儘管如此，有興趣及早檢查的人們，也應該考慮一下多早算早的問題。當然，我們寧願早些診斷微小的乳腺腫塊是不是癌症，也不願意坐視它發展成大腫塊。但如果就此推論，應當尋找顯微鏡才能看到的微小腫塊，恐怕就過頭了。韓國發現的許多甲狀腺癌變的尺寸不足一釐米。如果我們去尋找癌變的話，總能發現更多病例。但超過了一個限度，我們確診出的問題就太多了，還不如讓它們留在那裏不被發現好。簡而言之，讓醫生不要那麼熱衷於發現早期的癌變，符合患者的利益。

That’s where epidemiology comes in. Too many epidemiologists concern themselves not with controlling infectious disease, but with hoping to find small health effects of environmental exposures — or worse, uncertain effects of minor genetic alterations. Perhaps they should instead monitor the more important risk to human health: epidemics of medical care.

這正是流行病學的意義。太多的流行病專家不是關注於控制傳染病，而是希望尋找環境暴露因素對健康產生的微小影響，更糟的是，尋找微小基因差異可能產生的影響。或許他們應該去關注人類健康更重要的風險：醫療界造成的流行病。