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HOME | Hereditary Non-Polyposis Colorectal Cancer Syndrome
甚麼是遺傳性（非瘜肉）結直腸癌綜合症？
What is Hereditary Non-Polyposis Colorectal Cancer (HNPCC)?
According to statistics, Hong Kong had more than 2,800 new cases of large bowel cancer in 1996 and about half of them will die of this disease. The large bowel includes the colon and the rectum. Sometimes, the term colorectal cancer is used if either area of the large bowel is affected. Unlike the small bowel which is responsible for the digestion of our food, the role of the colon is to remove fluid from the liquid waste remaining after digestion. The rectum is a holding area for stool, the final form of this waste.
Researchers tell us that about 5 - 10% of all large bowel cancers are hereditary, that is, not only is there a family pattern but also an inherited predisposition for colorectal cancer in each generation. In the general population, it takes years for normal bowel cells to be damaged enough by diet or by other environmental influences to become a cancer affecting a 60 to 70 year old individual. However, the risk of developing a bowel cancer by age 40 to 50 years is much higher when several members of the same family are similarly affected.
Although there is no specific pattern for hereditary bowel cancer in every family, we can recognize one or more of the following features :
· Early onset of colon cancer before age 50 is an important clue
· The relationship and number of relatives with colon cancer will influence your risk of being affected
· One or more tumors may develop in the same family member
· In some individuals, colon cancer may be preceded by multiple mushroom-shaped growths or polyps inside the colon; these polyps are precancerous and are known as adenomas
· In some first- or second- degree relatives, associated cancers may occur, for example, in the uterus, ovaries, stomach, or urological tract. Gynaecologic or gastrointestinal screening is recommended when there is a family history of these malignancies.
Who is at risk?
Each FIRST-DEGREE RELATIVE, that is, each child, brother, and sister of an individual with hereditary colon cancer, has a 50 per cent chance of inheriting or not inheriting the disease gene. The disease does not appear to skip generations. Bowel cancer in SECOND-DEGREE RELATIVES (grandparents, aunts, and uncles) may clarify this family history because of their age when a cancer may have already occurred. Sometimes, it is difficult to confirm the disease in key family members due to early death; lack of medical records; adoption; or divorce. Other times, families may lose contact and be unaware of the state of health of first - or second- degree relatives.
If an individual has THREE or more FIRST-DEGREE RELATIVES (parent, sibling, child) with colon cancer, the risk of developing cancer of the large bowel is more than ten times that of the general population.
The family tree below illustrates how a parent may pass the disease gene on to one or more of her children. The risk remains the same for each pregnancy. In other words, in Generation 1, the grandmother developed colon cancer at age 44. She has 3 children and her 37-year-old son was affected in Generation 2. He has 4 daughters and 3 were diagnosed with hereditary colon cancer at ages 45, 41, and 40 years, respectively, in Generation 3. It is important to remember that the 2 children of his unaffected daughter are not considered at the same 50% risk as their 3 cousins in Generation 4.
How is Hereditary Colon Cancer Diagnosed?
Warning signs may be present in some cases : rectal bleeding; crampy abdominal pain or discomfort; persistent change in bowel habit (constipation or diarrhoea); or unexplained weight loss. However, often there are NO OBVIOUS SYMPTOMS. Knowing your family history can be your most important clue. A bowel lesion such as a polyp or cancer may only be diagnosed on one of the following tests. How often these examinations are done depends on your age and your family pattern of colon cancer. However, it is always best to screen for the disease PRIOR to any signs developing.
Flexible Sigmoidoscopy - The insertion of a short flexible fibreoptic tube to examine about 60 cm or 2 feet of the lower bowel (rectum and sigmoid colon). A pair of forceps may be passed through the scope to remove bowel tissue for examination under the microscope. This test can be done as outpatient. No sedation is required. However, not all of the colon is assessed.
Air-Contrast Barium Enema - An X-ray to outline the entire large bowel with BARIUM, a chalk-like substance. Unless the colon is completely empty after taking a specific bowel preparation, lesions may be missed. Biopsy is not possible during this procedure.
Colonoscopy - The passage of a long flexible fibreoptic tube into the whole length of the large bowel, about 1.5 meters or 5 feet. Biopsy of bowel tissue or removal of small polyps can be carried out at the same time. Careful bowel preparation is required. Sedation is given for this examination which may be done as a day-patient or in-patient in the hospital. It is a more uncomfortable but more complete procedure in highlighting the entire colon. Colonoscopy is the screening procedure of choice for hereditary colon cancer.
How is Hereditary Colon Cancer Treated?
There are three main ways to treat cancer of the large bowel : surgery, radiation therapy, and chemotherapy.
1. Surgery
This is the most effective form of treatment. Depending on the size of the tumor and its location in the large bowel, one of the following operations may be recommended :
Colectomy and Ileorectal Anastomosis - The removal of the large bowel or COLON and joining of the last part of the small intestine or ILEUM to the rectum. This is the recommended treatment for hereditary colon cancer.
Right or Left Hemicolectomy - The removal of half of the large intestine and reconnection of the healthy remainder.
Colostomy - The creation of an opening or STOMA in the abdomen for the elimination of body wastes using an external appliance. If the tumor is blocking the bowel, either a temporary or a permanent colostomy may be created after the tumor is removed. If it is temporary, a second operation will be needed to close the stoma once the bowel has healed and normal bowel function can be restored. An ENTEROSTOMAL THERAPIST is a nurse specially trained to teach a patient how to care for his or her own colostomy. It is important to remember that having a colostomy does not mean that you cannot resume your activities or lifestyle. This procedure is required less frequently now thanks to more modern surgical techniques.
Depending on your unique circumstances, including the site of the tumor, your surgeon will explain the different treatment options suitable for you and will help you in deciding on the type of operation needed.
One of the ways cancer can METASTASIZE or spread through the body is through the LYMPH SYSTEM. During your operation, the surgeon will remove lymph nodes to look for any cancer cells. Sometimes, more treatment will be needed, either before or after your surgery.
2. Radiation Therapy
The use of high-energy rays to stop cancer cells from growing and increasing. This may be done preoperatively to shrink the tumor or postoperatively to remove any remaining cancer cells. Radiation may be particularly helpful for a cancer of the rectum. Should you require radiation, you can have this done as an outpatient. Your doctor will discuss the possible side effects of radiation and what you can do with the support of the medical team looking after you.
3. Chemotherapy
The use of oral or injected drugs to treat cancer. The drugs travel through the bloodstream to almost every area of the body. Chemotherapy may be suggested after your operation or radiation therapy for any cancer cells which are left. This is most commonly done in cycles with a resting period in-between. Sometimes, chemotherapy is started in the hospital, then continued on an outpatient basis or at home. Chemotherapy has been suggested for some forms of colonic or rectal cancers. Since your appetite may be affected, the dietitian will help you work out ways to ensure good nutrition during this period.
Why is Screening Important?
The only way to find out whether you are at risk for hereditary colon cancer is to take preventive steps. This, in turn, will allow you to have the appropriate screening test to meet your needs, based on your age and your family history of cancer. Research has allowed the identification of the genes responsible for hereditary colon cancer. Genetic testing is feasible to identify the diseased gene in a family. This usually starts from testing family members who have already developed cancers. Result of molecular genetic testing will further assist in defining your cancer risk so that the most appropriate screening plan can be devised for you.
Where is Help Available?
Contact the Hereditary Gastrointestinal Cancer Registry based at Queen Mary Hospital to learn more about your family cancer pattern. A family tree will be developed so that you can understand your own risk and that of your first-degree relatives. The Registry can provide more information concerning current treatment and research on hereditary colon cancer. Patients can be referred through the Registry for treatment in specialist centres when required. Support is offered through the Registry so that you can participate more fully in your health care and that of your family. Cancer prevention is effective but it will not happen without you. Start today.
If we can be of assistance, please feel free to contact us.
根據統計數字顯示，在1996年香港有超過2,800宗患大腸癌的新個案，當中超過一半會死於大腸癌。大腸包括結腸和直腸。所以有時我們也稱大腸癌為結直腸癌。小腸負責消化食物，結腸的功能是負責吸收消化後產生的流質廢物內的液體。直腸則用作儲存糞便。即人體排泄物的最後形體。
研究人員指出百份之5-10的大腸癌是遺傳的，意思是說這些癌症患者不單止是有家族形式可尋，而且是每一代都有患結直腸癌的遺傳傾向。對於一般人士，正常的大腸細胞需要多年時間經食物或其他環境的破壞至其達60-70歲才會變成癌細胞。可是，如果家裡有幾個成員都患上結直腸癌，那麼其他家庭成員在40-50歲時患上癌症的風險便相應大大提高。
雖然每一個患有遺傳性大腸癌的家庭都沒有一個指定的模式，但我們可以看到以下一至數個的特徵：
50歲前便患結直腸癌是一個重要的提示
與患結直腸癌的親屬的關係及其數目會影響你患癌的風險
同一個家庭成員有多過一個的腫瘤
一些個案是在患結直腸癌前，大腸內長了多個菇狀的物體（或稱瘜肉），這些癌症前的瘜肉稱為腺瘤
一些直屬或近親在子宮、卵巢、胃或泌尿道患上相關的癌症。若家族有這些惡性腫瘤的紀錄，則他們需要進行婦科或胃腸科普查。
誰有風險？
每一個患有遺傳性結直腸癌的人士，其直系親屬（意指子女兄弟姊妹）均有一半機會遺傳了病症的基因。病症不會隔代遺傳。近親（即祖父母、外祖父母、姑姨母、叔伯及舅父）的病歷有助了解家族的遺傳傾向。因為以他們的年紀，癌症可能已經出現了。有的時候因為家庭成員早逝、缺乏病歷、收養、離婚，要確定病症比較困難。此外一些家庭可能與其他成員失去聯絡，以致未能確知直系或近親的健康情況。
若個人家中有三個或以上的直系親屬（即父母、兄弟姊妹、子女）患有大腸癌，那麼他患上大腸癌的機會是一般人的十倍或以上。
以下的家族譜可以顯示父母怎樣將病症基因遺傳給一個或多個子女。每次懷孕把基因遺傳給子女的機會都是一樣。換句話說在第一代，祖母在44歲患大腸癌，其第二代的3個子女中，37歲的兒子患病。這個兒子的4 個女兒（第三代），3個分別在45歲、41歲、40歲時證實患了遺傳性結直腸癌。這裡要著重一提的是，沒有受影響之女兒的兩名子女（即第四代）患癌的機會是遠低於他們的表親。
怎樣診斷患有遺傳性大腸癌？
一些情況是有警告訊息的：例如排便時出血，腹部絞痛或不適；大便習慣持續改變（即持續便秘或腹瀉）；不明的體重下降。但很多時瘜肉及早期的癌瘤都沒有明顯的病徵。知 道家族的病史可能是你最重要的線索。對於受遺傳性結直腸癌影響的人士，在無病徵期以定期普查找出瘜肉或早期的癌症是最好的方法。檢查需隔多久進行一次則視乎個人年齡及家族患癌的模式而定。
結直腸的檢查方法如下：
乙狀結腸及直腸內窺鏡 — 把一支60厘米長（或兩呎）的光纖管內窺鏡從肛門插入，檢查直腸及乙狀結腸。如有需要，可以鉗子通過內窺鏡取出活組織作顯微鏡分析。這項檢查毋須入院進行，也不需鎮靜劑，但缺點是未能檢查全條結直腸。
鋇灌腸X光造影術 — 利用鋇 — 一種石灰狀的物體，以X光繪出整條大腸的形狀，檢查前需飲用灌腸劑以清洗腸道。這項程序不能抽取活組織作分析。
結直腸內窺鏡 — 把一支約1.5米長（或五呎）長的彎曲光纖管放入整條大腸。抽取組織或切除細小的瘜肉可同時進行。需小心清洗腸道。這種檢查可以日間診治或住院形式進行，有需要時會用鎮靜劑的。檢查方式較前者不適但更全面。結直腸內窺鏡的普查程序會用於遺傳性結直腸癌的人仕。
怎樣醫治遺傳性結直腸癌？
醫治大腸癌有三種主要的方法：外科手術、放射治療和化學治療。
外科手術
這種方法最有效。按腫瘤在大腸的位置和大小而定，可建議採用以下的手術方式：
結腸切除及迴直腸吻合手術
將整條結腸切除，同時將小腸的尾段（即迴腸）接上直腸。是治療遺傳性結直腸癌的方法。
切除右或左結腸
切去一半的結腸然後接上餘下健全的大腸。
結腸造口手術
在腹部開一個「人工造口」或稱「假肛」以作排泄用。若腫瘤阻礙排便，在腫瘤切除後可暫時或永久安上結腸造口。臨時的造口須於排便運作正常後再進行手術把造口封閉。腸造口術治療師是一名經過特別訓練，教導病人如何護理自己結腸造口的護士。一點須緊記的是有造口的病人不就代表日常活動受到限制。現代先進的科技甚少需要這種步驟了。
你的醫生會就你的情況，包括腫瘤的位置，而決定那一種手術最為適合。
淋巴組織是癌細胞轉移或擴散的其中一個途徑。手術期間，醫生會將淋巴結切除找出是否有癌細胞。有的時候在手術前或後可能要進行一些輔助治療。
放射治療（簡稱電療）
利用高能量光線阻止癌細胞生長和增加。可於手術前將腫瘤縮細或於手術後把剩餘的癌細胞消除。放射治療對直腸癌最為有效。放射治療可於門診部進行，主診醫生會解釋出現副作用的可能和從醫療隊伍所得到的協助。
化學治療（簡稱化療）
以口服或注射方式治療癌症，藥物經血管帶到全身。化療可能在手術或放射治療後用作清除剩餘的細胞，一般以週期進行，當中也有歇息期。有時化療會在醫院開始，然後在門診或家中進行。化學治療通常會建議給結直腸癌患者。治療期間，胃口會受到影響，營養師會提供協助確保你有足的營養完成這個療程。
為甚麼普查重要？
預防是找出你是否受遺傳性結直腸癌威脅的唯一方法。根據你的年歲及家族患癌的紀錄而作出適當的普查測試以配合個人所需，研究可找出引致遺傳性結直腸癌的基因。遺傳基因測試可鑒定家族的有病基因，這種測驗通常由家中已患病的成員開始；分子遺傳基因測試的結果可協助告知你患癌的機會，以便設計出一個最合適的普查計劃。
向何處求助？
如果你想知多一點有關你家族腸癌症的模式，你可與瑪麗醫院的遺傳性腸胃癌資料庫聯絡。資料庫會幫助你列出族譜，這有助你了解自己和直屬親人的患癌機會。我們也會提供更多關於現時治療遺傳性結直腸癌的方法和研究資料。病人如有需要會由資料庫轉介往專科治療。資料庫也希望向你提供協助使你更全面參與你和家人的健康護理。預防癌症又怎能沒有你的參與呢？就讓我們從今天開始吧。
如需協助，請與我們聯絡。
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