什么是癌症预防？
癌症预防是采取措施以降低患癌几率。通过癌症预防能够减少群体中癌症的新发病例,并有希望降低癌症死亡人数。
科学家们从危险因素和保护因素两方面着手研究癌症的预防。任何增加患癌风险的因素被称为癌症的危险因素；而任何降低患癌风险的因素被称为保护因素。
人们可以避免癌症的一些危险因素，但仍有许多危险因素不可避免。比如，吸烟和某些遗传基因均是某类癌症的危险因素，但只有吸烟可以避免。规律运动、健康饮食是某类癌症的保护因素。避免危险因素、增加保护因素也许能降低患癌风险，但并不意味着不会患癌。
目前正在研究中的一些预防癌症的方法，包括：
What is prevention?
Cancer prevention is action taken to lower the chance of getting cancer. By preventing cancer, the number of new cases of cancer in a group or population is lowered. Hopefully, this will lower the number of deaths caused by cancer.
To prevent new cancers from starting, scientists look at risk factors and protective factors. Anything that increases your chance of developing cancer is called a cancer risk factor; anything that decreases your chance of developing cancer is called a cancer protective factor.
Some risk factors for cancer can be avoided, but many cannot. For example, both smoking and inheriting certain genes are risk factors for some types of cancer, but only smoking can be avoided. Regular exercise and a healthy diet may be protective factors for some types of cancer. Avoiding risk factors and increasing protective factors may lower your risk, but it does not mean that you will not get cancer.
Different ways to prevent cancer are being studied, including:
关于结直肠癌的基本信息
结直肠癌是结肠或直肠组织中出现恶性（癌）细胞的疾病。
结肠是人体消化系统的一部分。消化系统吸收并处理食物中的营养物质（包括维生素、矿物质、碳水化合物、脂肪、蛋白质和水），并将代谢废物排出体外。消化系统包括口腔、咽、食管、胃、小肠和大肠。结肠（大肠）约1.5米长，是大肠的第一部分。大肠的最后一部分由直肠和肛管组成，约15-20厘米长。肛管末端为肛门（大肠末端通向体外的开口）。
下消化系统的解剖图，显示结肠和其他器官。
癌症始于结肠称为结肠癌，始于直肠称为直肠癌。累及以上任一器官的也可称为结直肠癌。
更多有关结直肠癌信息请参考以下PDQ概述：
结直肠癌是美国第三大癌症致死原因。
在≥55岁的成年人中，结直肠癌的新增病例数和死亡病例数每年略有下降。然而，在55岁以下的成年人中，近年来结直肠癌新发病例数在缓慢增加。非裔美国人结直肠癌新增病例数和死亡病例数高于其他种族人群。
早发现、早治疗结直肠癌可以降低结肠癌死亡率。可通过筛检发现结直肠癌。
General Information About Colorectal Cancer
Colorectal cancer is a disease in which malignant (cancer) cells form in the tissues of the colon or the rectum.
The colon is part of the body's digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the mouth, throat, esophagus, stomach, and the small and large intestines. The colon (large bowel) is the first part of the large intestine and is about 5 feet long. Together, the rectum and anal canal make up the last part of the large intestine and are 6 to 8 inches long. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).
Anatomy of the lower digestive system, showing the colon and other organs.
Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer. Cancer that affects either of these organs may also be called colorectal cancer.
See the following PDQ summaries for more information about colorectal cancer:
Colorectal cancer is the third leading cause of death from cancer in the United States.
The number of new colorectal cancer cases and the number of deaths from colorectal cancer are both decreasing a little bit each year in adults aged 55 and older. However, in adults younger than 55 years, the number of new colorectal cancer cases has slowly increased in recent years. The number of new colorectal cancers and deaths from colorectal cancer are higher in African Americans than in other races.
Finding and treating colorectal cancer early may prevent death from colorectal cancer. Screening tests may be used to help find colorectal cancer.
结直肠癌的预防
避免危险因素、增加保护因素可能有助于预防癌症。
避免危险因素，如吸烟、超重和缺乏锻炼；增加保护因素，如戒烟和锻炼，都可能有助于预防某些癌症。可以与医生或其他健康保健专家咨询如何降低癌症风险。
以下因素会增加结直肠癌风险：
年龄
50岁以后，患结直肠癌的风险会增高。多数结直肠癌在50岁后确诊。
结直肠癌家族史
父母、兄弟姐妹或子女患结直肠癌者，个体患结直肠癌的风险约增加1倍。
个人史
有以下个人史的个体，患结直肠癌的风险增加：
遗传风险
某些遗传性疾病、家族性腺瘤性息肉病（FAP）或遗传性非息肉病性结直肠癌（HNPCC或Lynch综合征）与特定基因改变有关，进而引起患结直肠癌的风险增加。
酒精
每天饮用酒精饮料三杯或三杯以上会增加患结直肠癌的风险。同时饮酒也可能导致结直肠大腺瘤（良性肿瘤）的风险。
吸烟
吸烟会增加结直肠癌的发病及死亡。
吸烟同时也会增加患结直肠腺瘤的风险。吸烟者肠镜摘除腺瘤后的复发风险更高。
种族
与其他种族相比，非裔美国人结直肠癌的发病风险和死亡风险更高。
肥胖
肥胖会增加结直肠癌的发病及死亡。
以下保护性因素可降低结直肠癌的风险：
体力活动。
包括规律的体力活动在内的生活方式可以降低患结直肠癌的风险。
阿司匹林
研究显示，服用阿司匹林可以降低结直肠癌的发病风险和死亡风险。但这种获益，在病人服药后的10至20年才开始显现出来。
每天或每隔一天小剂量（≤100毫克）服用阿司匹林，可能会增加中风和胃肠道出血的风险。其中老年人、男性和高出血风险人群的风险性更高。
联合激素替代治疗：
研究显示，包括雌激素和黄体酮的联合激素替代疗法（HRT）可降低绝经后妇女浸润性结直肠癌的风险。
然而，接受联合激素替代治疗的结直肠癌女性患者在诊断时病情多为晚期，晚期结直肠癌预后不佳，因而结直肠癌的死亡率并未降低。
联合激素替代治疗可能会使以下疾病的发病风险增加:
息肉摘除
大多数结直肠息肉为腺瘤，被认为是结直肠癌的癌前病变阶段。能够在早期阶段发现并摘除大于1厘米（豌豆大小）的结直肠息肉可降低患结直肠癌的风险。目前还不清楚结直肠小息肉的摘除是否能降低患结直肠癌的风险。
采用结肠镜检查或乙状结肠镜检查摘除息肉可能会导致结肠壁破裂出血。
结肠息肉。有些息肉有蒂，有些没有。插图显示带蒂息肉的照片。
目前还不清楚以下因素是否会影响结直肠癌的风险:
除阿司匹林外的非甾体类抗炎药物（NSAID）
目前尚不清楚非甾体抗炎药或NSAID（如舒林酸、塞来昔布、萘普生和布洛芬）是否能降低结直肠癌的风险。
研究显示，服用非甾体抗炎药塞来昔布可降低结直肠腺瘤（良性肿瘤）摘除后复发的风险。目前还不清楚这是否会降低患结直肠癌的风险。
目前已证明，对于具有家族性腺瘤性息肉（FAP）的人而言，服用舒林酸或塞来昔布可以减少在结肠和直肠中形成的息肉数量和大小。目前还不清楚这是否会降低患结直肠癌的风险。
非甾体类抗炎药物的副作用：
钙
服用钙补充剂对预防结直肠癌是否有效尚不明确。
饮食
减少脂肪和肉类的摄入，增加膳食纤维、果蔬的食用是否能够预防结直肠癌也尚不清楚。
一些研究显示，高脂肪、高蛋白、高热量和多肉类的饮食，会增加患结直肠癌的风险，而有些研究结果却恰恰相反。
以下因素不影响结直肠癌的风险:
雌激素替代疗法
雌激素替代疗法不能降低浸润性结直肠癌的发病和死亡风险。
他汀类药物
研究显示，服用他汀类药物（降低胆固醇的药物）不会增加或降低结直肠癌的风险。
癌症预防临床试验旨在研究预防癌症的方法。
癌症预防临床试验是研究如何降低某些癌症的发病风险。有些癌症预防试验是针对肿瘤高危人群开展的研究。有些则是针对现患病例，预防肿瘤复发和再发开展的研究。还有一些试验是选择健康人志愿者开展研究。
癌症预防临床试验的目的是判断采取的各种措施能否有效预防癌症。这些措施包括增强锻炼、戒烟、服用某些药物或维生素或矿物质或其他食品补充剂。
预防结直肠癌的新方法正在临床试验中。
有关NCI支持的临床试验的信息，可在NCI的临床试验搜索网页上找到。其他组织支持的临床试验可以在ClinicalTrials.gov网站上找到。
Colorectal Cancer Prevention
Avoiding risk factors and increasing protective factors may help prevent cancer.
Avoiding cancer risk factors may help prevent certain cancers. Risk factors include smoking, being overweight, and not getting enough exercise. Increasing protective factors such as quitting smoking and exercising may also help prevent some cancers. Talk to your doctor or other health care professional about how you might lower your risk of cancer.
The following risk factors increase the risk of colorectal cancer:
Age
The risk of colorectal cancer increases after age 50. Most cases of colorectal cancer are diagnosed after age 50.
Family history of colorectal cancer
Having a parent, brother, sister, or child with colorectal cancer doubles a person's risk of colorectal cancer.
Personal history
Having a personal history of the following conditions increases the risk of colorectal cancer:
Inherited risk
The risk of colorectal cancer is increased when certain gene changes linked to familial adenomatous polyposis (FAP) or hereditary nonpolyposis colon cancer (HNPCC or Lynch Syndrome) are inherited.
Alcohol
Drinking 3 or more alcoholic beverages per day increases the risk of colorectal cancer. Drinking alcohol is also linked to the risk of forming large colorectal adenomas (benign tumors).
Cigarette smoking
Cigarette smoking is linked to an increased risk of colorectal cancer and death from colorectal cancer.
Smoking cigarettes is also linked to an increased risk of forming colorectal adenomas. Cigarette smokers who have had surgery to remove colorectal adenomas are at an increased risk for the adenomas to recur (come back).
Race
African Americans have an increased risk of colorectal cancer and death from colorectal cancer compared to other races.
Obesity
Obesity is linked to an increased risk of colorectal cancer and death from colorectal cancer.
The following protective factors decrease the risk of colorectal cancer:
Physical activity
A lifestyle that includes regular physical activity is linked to a decreased risk of colorectal cancer.
Aspirin
Studies have shown that taking aspirin lowers the risk of colorectal cancer and the risk of death from colorectal cancer. The decrease in risk begins 10 to 20 years after patients start taking aspirin.
The possible harms of aspirin use (100 mg or less) daily or every other day include an increased risk of stroke and bleeding in the stomach and intestines. These risks may be greater among the elderly, men, and those with conditions linked to a higher than normal risk of bleeding.
Combination hormone replacement therapy
Studies have shown that combination hormone replacement therapy (HRT) that includes both estrogen and progestin lowers the risk of invasive colorectal cancer in postmenopausal women.
However, in women who take combination HRT and do develop colorectal cancer, the cancer is more likely to be advanced when it is diagnosed and the risk of dying from colorectal cancer is not decreased.
The possible harms of combination HRT include an increased risk of having:
Polyp removal
Most colorectal polyps are adenomas, which may develop into cancer. Removing colorectal polyps that are larger than 1 centimeter (pea-sized) may lower the risk of colorectal cancer. It is not known if removing smaller polyps lowers the risk of colorectal cancer.
The possible harms of polyp removal during colonoscopy or sigmoidoscopy include a tear in the wall of the colon and bleeding.
Polyps in the colon. Some polyps have a stalk and others do not. Inset shows a photo of a polyp with a stalk.
It is not clear if the following affect the risk of colorectal cancer:
Nonsteroidal anti-inflammatory drugs (NSAIDs) other than aspirin
It is not known if the use of nonsteroidal anti-inflammatory drugs or NSAIDs (such as sulindac, celecoxib, naproxen, and ibuprofen) lowers the risk of colorectal cancer.
Studies have shown that taking the nonsteroidal anti-inflammatory drug celecoxib reduces the risk of colorectal adenomas (benign tumors) coming back after they have been removed. It is not clear if this results in a lower risk of colorectal cancer.
Taking sulindac or celecoxib has been shown to reduce the number and size of polyps that form in the colon and rectum of people with familial adenomatous polyposis (FAP). It is not clear if this results in a lower risk of colorectal cancer.
The possible harms of NSAIDs include:
Calcium
It is not known if taking calcium supplements lowers the risk of colorectal cancer.
Diet
It is not known if a diet low in fat and meat and high in fiber, fruits, and vegetables lowers the risk of colorectal cancer.
Some studies have shown that a diet high in fat, proteins, calories, and meat increases the risk of colorectal cancer, but other studies have not.
The following factors do not affect the risk of colorectal cancer:
Hormone replacement therapy with estrogen only
Hormone replacement therapy with estrogen only does not lower the risk of having invasive colorectal cancer or the risk of dying from colorectal cancer.
Statins
Studies have shown that taking statins (drugs that lower cholesterol) does not increase or decrease the risk of colorectal cancer.
Cancer prevention clinical trials are used to study ways to prevent cancer.
Cancer prevention clinical trials are used to study ways to lower the risk of developing certain types of cancer. Some cancer prevention trials are conducted with healthy people who have not had cancer but who have an increased risk for cancer. Other prevention trials are conducted with people who have had cancer and are trying to prevent another cancer of the same type or to lower their chance of developing a new type of cancer. Other trials are done with healthy volunteers who are not known to have any risk factors for cancer.
The purpose of some cancer prevention clinical trials is to find out whether actions people take can prevent cancer. These may include exercising more or quitting smoking or taking certain medicines, vitamins, minerals, or food supplements.
New ways to prevent colorectal cancer are being studied in clinical trials.
Information about clinical trials supported by NCI can be found on NCI’s clinical trials search webpage. Clinical trials supported by other organizations can be found on the ClinicalTrials.gov website.
About This PDQ Summary
About PDQ
Physician Data Query (PDQ) is the National Cancer Institute's (NCI's) comprehensive cancer information database. The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health professional versions have detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions have cancer information that is accurate and up to date and most versions are also available in Spanish.
PDQ is a service of the NCI. The NCI is part of the National Institutes of Health (NIH). NIH is the federal government’s center of biomedical research. The PDQ summaries are based on an independent review of the medical literature. They are not policy statements of the NCI or the NIH.
Purpose of This Summary
This PDQ cancer information summary has current information about colorectal cancer prevention. It is meant to inform and help patients, families, and caregivers. It does not give formal guidelines or recommendations for making decisions about health care.
Reviewers and Updates
Editorial Boards write the PDQ cancer information summaries and keep them up to date. These Boards are made up of experts in cancer treatment and other specialties related to cancer. The summaries are reviewed regularly and changes are made when there is new information. The date on each summary ("Updated") is the date of the most recent change.
The information in this patient summary was taken from the health professional version, which is reviewed regularly and updated as needed, by the PDQ Screening and Prevention Editorial Board.
Clinical Trial Information
A clinical trial is a study to answer a scientific question, such as whether one treatment is better than another. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients. During treatment clinical trials, information is collected about the effects of a new treatment and how well it works. If a clinical trial shows that a new treatment is better than one currently being used, the new treatment may become "standard." Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.
Clinical trials can be found online at NCI's website. For more information, call the Cancer Information Service (CIS), NCI's contact center, at 1-800-4-CANCER (1-800-422-6237).
Permission to Use This Summary
PDQ is a registered trademark. The content of PDQ documents can be used freely as text. It cannot be identified as an NCI PDQ cancer information summary unless the whole summary is shown and it is updated regularly. However, a user would be allowed to write a sentence such as “NCI’s PDQ cancer information summary about breast cancer prevention states the risks in the following way: [include excerpt from the summary].”
The best way to cite this PDQ summary is:
PDQ® Screening and Prevention Editorial Board. PDQ Colorectal Cancer Prevention. Bethesda, MD: National Cancer Institute. Updated
Images in this summary are used with permission of the author(s), artist, and/or publisher for use in the PDQ summaries only. If you want to use an image from a PDQ summary and you are not using the whole summary, you must get permission from the owner. It cannot be given by the National Cancer Institute. Information about using the images in this summary, along with many other images related to cancer can be found in Visuals Online. Visuals Online is a collection of more than 3,000 scientific images.
Disclaimer
The information in these summaries should not be used to make decisions about insurance reimbursement. More information on insurance coverage is available on Cancer.gov on the Managing Cancer Care page.
Contact Us
More information about contacting us or receiving help with the Cancer.gov website can be found on our Contact Us for Help page. Questions can also be submitted to Cancer.gov through the website’s E-mail Us.
About This PDQ Summary
About PDQ
Physician Data Query (PDQ) is the National Cancer Institute's (NCI's) comprehensive cancer information database. The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health professional versions have detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions have cancer information that is accurate and up to date and most versions are also available in Spanish.
PDQ is a service of the NCI. The NCI is part of the National Institutes of Health (NIH). NIH is the federal government’s center of biomedical research. The PDQ summaries are based on an independent review of the medical literature. They are not policy statements of the NCI or the NIH.
Purpose of This Summary
This PDQ cancer information summary has current information about colorectal cancer prevention. It is meant to inform and help patients, families, and caregivers. It does not give formal guidelines or recommendations for making decisions about health care.
Reviewers and Updates
Editorial Boards write the PDQ cancer information summaries and keep them up to date. These Boards are made up of experts in cancer treatment and other specialties related to cancer. The summaries are reviewed regularly and changes are made when there is new information. The date on each summary ("Updated") is the date of the most recent change.
The information in this patient summary was taken from the health professional version, which is reviewed regularly and updated as needed, by the PDQ Screening and Prevention Editorial Board.
Clinical Trial Information
A clinical trial is a study to answer a scientific question, such as whether one treatment is better than another. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients. During treatment clinical trials, information is collected about the effects of a new treatment and how well it works. If a clinical trial shows that a new treatment is better than one currently being used, the new treatment may become "standard." Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.
Clinical trials can be found online at NCI's website. For more information, call the Cancer Information Service (CIS), NCI's contact center, at 1-800-4-CANCER (1-800-422-6237).
Permission to Use This Summary
PDQ is a registered trademark. The content of PDQ documents can be used freely as text. It cannot be identified as an NCI PDQ cancer information summary unless the whole summary is shown and it is updated regularly. However, a user would be allowed to write a sentence such as “NCI’s PDQ cancer information summary about breast cancer prevention states the risks in the following way: [include excerpt from the summary].”
The best way to cite this PDQ summary is:
PDQ® Screening and Prevention Editorial Board. PDQ Colorectal Cancer Prevention. Bethesda, MD: National Cancer Institute. Updated
Images in this summary are used with permission of the author(s), artist, and/or publisher for use in the PDQ summaries only. If you want to use an image from a PDQ summary and you are not using the whole summary, you must get permission from the owner. It cannot be given by the National Cancer Institute. Information about using the images in this summary, along with many other images related to cancer can be found in Visuals Online. Visuals Online is a collection of more than 3,000 scientific images.
Disclaimer
The information in these summaries should not be used to make decisions about insurance reimbursement. More information on insurance coverage is available on Cancer.gov on the Managing Cancer Care page.
Contact Us
More information about contacting us or receiving help with the Cancer.gov website can be found on our Contact Us for Help page. Questions can also be submitted to Cancer.gov through the website’s E-mail Us.