If you were to lay your digestive tract out in a straight line,

如果將消化道拉成一直線，

it would form a tube spanning nearly ten meters.

它將會是一條長度近十公尺的管道。

The last 1.5 meters of that are called the colon, or large intestine.

尾端一點五公尺被稱為結腸或大腸。

Cells in this organ's lining constantly renew themselves,

結腸的內層細胞會不斷更新替換，

but the genes that moderate this process occasionally go awry,

但有時負責調控此步驟的基因會失靈，

leading to the excessive growth of new cells.

導致新細胞過度增生。

That results in small growths or abnormal clumps of cells called polyps.

產生小腫塊或是不正常細胞結塊，被稱為「息肉」

The majority of these polyps won't do any harm,

大多數息肉都不是有害的，

but some can become cancerous when their cells begin to grow and divide rapidly,

但有些息肉會快速生長分裂，變成惡性腫瘤，

projecting further into the colon.

並繼續深入結腸內部。

At that point, they can transform into colon cancer,

這時，它們就成了結腸癌──

one of the most prevalent and preventable forms of cancer in the world.

世界上最盛行，也最容易預防的癌症之一。

That's a slow process:

該癌症病程變化不快，

though growth times vary,

雖然成長速度不一，

it often takes around ten years for a small polyp to grow and develop into a cancerous one.

但小息肉通常需要十年左右時間才會長成惡性腫瘤。

We don't know exactly what causes the majority of colon polyps and colon cancers.

我們不清楚大多數結腸息肉和結腸癌的確切成因。

We do know in general that colon cancer involves the activation of what's called oncogenes in the polyp,

但確實知道通常結腸癌的發生和激活息肉裡的「致癌基因」

and/or the loss of tumor-suppressor genes that usually keep cancer cells in check.

還有／或是抑癌基因的消失有關。

Most cells have proto-oncogenes that help them grow.

多數細胞都具備「原致癌基因」 幫助其成長。

When a proto-oncogene mutates, or there are two many copies of it,

一旦原致癌基因發生突變，或是複製過多，

it can become a permanently active oncogene with cells that grow out of control.

就可能轉變成永久活躍的致癌基因，並以失控的速度分裂。

While we don't yet know exactly what underlying factors cause these changes,

目前還不知道是哪些潛在因素導致這些變化，

experts suspect a combination of both environmental and inherited genetic factors.

不過專家們懷疑是環境及基因遺傳兩相結合的結果。

In the worst cases, when cells within polyps divide and spread unchecked,

最糟糕的情況下，息肉裡的細胞不受控制的分裂並擴散，

they eventually break through the lining of the colon.

最終突破結腸內層。

Lymph and blood vessels carry those cells all over the body, and they can go on to form tumors.

淋巴和血管會將這些細胞帶到全身，並在身體各個部位產生腫瘤。

Despite these challenges, there's a solution.

雖然困難重重，但此病並不是無解。

We've become extremely good at detecting and removing offending polyps before they can cause cancer.

現今醫學在檢測及移除可能癌變息肉這塊，早已爐火純青。

This happens through a process called screening,

而這會透過「疾病篩檢」來實施。

and when we do it regularly, we can prevent many cases of colon cancer.

只要定期篩檢，就可以預防許多結腸癌的發生。

So, who's at risk?

那麼，誰是高危險群呢？

Most cases occur in people aged 50 years or older.

大部分病例好發於五十歲以上人群。

This group is considered at average risk for colon cancer or colon polyps.

這族群被認為普遍有罹患結腸癌或結腸息肉的風險。

There's also a higher risk group that includes people with personal or family histories of colon polyps or cancer,

還有個更高風險的群體，包括有結腸息肉或癌症個人或家族史，

and those who suffer from inherited genetic syndromes, or inflammatory diseases,

以及患有遺傳症狀，或苦於發炎性疾病之人，

like Crohn's disease and ulcerative colitis.

例如克隆氏症和潰瘍性大腸炎。

So the best age to initiate screening varies from person to person.

因此，開始進行定期篩檢的合適年齡因人而異。

If you have access to healthcare,

如果有機會獲取醫療保健，

it's best to consult a doctor to find out when you should begin.

最好諮詢醫師你開始篩檢的適當時機。

Screening can be done with various tests.

篩檢包含許多不同類型的測試。

Colonoscopy involves a long, thin, flexible tube that's fitted with a video camera and light at the end

「結腸鏡檢查」 指的是用一根有彈性，末端配有攝影鏡頭和燈源的細長管子

and placed internally to examine the colon for polyps.

深入體內檢查結腸是否有息肉。

If polyps are found, a doctor can do a polypectomy,

如果找到息肉，醫生就會進行「息肉切除術」，

a procedure that removes polyps from the colonic wall.

也就是將息肉從結腸壁上切除。

Doctors can also then test the polyp for cancerous cells.

之後，醫師就可以測試息肉中是否有癌細胞。

Colonoscopy is the only test that can be used to both find and remove polyps.

結腸鏡檢查是唯一可以同時找到並移除息肉的檢查。

There are, however, other useful screening tests,

還有其他有用的篩檢測試，

including imaging and at-home tests that can allow patients to examine their stool for small amounts of blood.

包含影像檢查和「居家檢測」，也就是請病人檢視他們排泄物中是否有血。

Occasionally, polyps are too large to be removed during a colonoscopy,

偶爾會有過大的息肉，無法通過結腸鏡檢查移除。

in which case, the next step is surgery.

此情況下，就得進行手術了。

If blood and imaging tests then reveal that cancerous cells have spread outside the colon,

若血液檢測及造影顯示癌細胞已擴散至結腸外部，

then a special treatment, like chemotherapy, may also be required to stop the cancer from escalating.

那像「化療」這種特殊治療，就是防止癌症惡化的必要措施。

We can also take on certain habits to reduce our likelihood of developing colon cancer in the first place.

我們也可以先培養一些特定習慣來降低得到結腸癌的機率。

There's evidence that maintaining a healthy weight, not smoking, and being physically active can help.

證據顯示，維持適當體重、不吸菸，還有保持運動習慣會有幫助。

But most importantly,

但最重要的是，

access to healthcare and regular screenings at crucial times in life are the best ways to prevent colon cancer.

在關鍵時刻尋求醫療協助和定期檢查是預防結腸癌的最佳方法。