Cancer is a generic term for a large group of diseases that can affect any part of the body. Other terms used are malignant tumors and neoplasms.
One defining feature of cancer is the rapid creation of abnormal cells that grow beyond their usual boundaries, and which can then invade adjoining parts of the body and spread to other organs. This process is referred to as metastasis. Metastases are the major cause of death from cancer.
癌症预防 Cancer prevention
至少三分之一的癌症病例可以得到预防。预防为癌症控制提供了最具成本效益的长期战略。
At least one-third of all cancer cases are preventable. Prevention offers the most cost-effective long-term strategy for the control of cancer.
烟草 Tabacco
烟草使用是全世界癌症死亡的单一最大可避免风险因素，估计每年导致22%的癌症死亡。2004年，740万癌症死者中，有160万由烟草使用导致。
吸烟可导致多种形式的癌症，包括肺癌、食道癌、喉癌、口腔癌、咽喉癌、肾癌、膀胱癌、胰腺癌、胃癌和宫颈癌。大约70%的肺癌负担单单由吸烟引起。二手烟（也称为环境烟草烟雾）已被证明能够使不吸烟者罹患肺癌。无烟烟草（也被称为口用烟草、嚼烟或鼻烟）可导致口腔癌、食道癌和胰腺癌。
Tobacco use is the single greatest avoidable risk factor for cancer mortality worldwide, causing an estimated 22% of cancer deaths per year. In 2004, 1.6 million of the 7.4 million cancer deaths were due to tobacco use.
Tobacco smoking causes many types of cancer, including cancers of the lung, oesophagus, larynx (voice box), mouth, throat, kidney, bladder, pancreas, stomach and cervix. About 70% of the lung cancer burden can be attributed to smoking alone. Second-hand smoke (SHS), also known as environmental tobacco smoke, has been proven to cause lung cancer in nonsmoking adults. Smokeless tobacco (also called oral tobacco, chewing tobacco or snuff) causes oral, oesophageal and pancreatic cancer.
缺乏运动、饮食因素、肥胖和超重
Physical Inactivity, dietary factors, obesity and being overweight
调整饮食是控制癌症的另外一项重要方法。超重和肥胖与多种类型的癌症相关，如食道癌、结肠直肠癌、乳腺癌、子宫内膜癌和肾癌。饮食中水果和蔬菜含量高可能对抵抗多种癌症起到保护作用。相反，过量食用红肉和腌制肉类可能会增加患结肠直肠癌的风险。另外，预防与饮食相关癌症的健康饮食习惯还能降低患心血管疾病的风险。
定期锻炼身体、保持健康体重加上健康饮食可大幅降低罹患癌症的风险。应实施国家政策和规划，以提高认识并减少对癌症风险因素的接触，保证向人们提供采用健康生活方式所需的信息和支持。
Dietary modification is another important approach to cancer control. There is a link between overweight and obesity to many types of cancer such as oesophagus, colorectum, breast, endometrium and kidney. Diets high in fruits and vegetables may have a protective effect against many cancers. Conversely, excess consumption of red and preserved meat may be associated with an increased risk of colorectal cancer. In addition, healthy eating habits that prevent the development of diet-associated cancers will also lower the risk of cardiovascular disease.
Regular physical activity and the maintenance of a healthy body weight, along with a healthy diet, will considerably reduce cancer risk. National policies and programmes should be implemented to raise awareness and reduce exposure to cancer risk factors, and to ensure that people are provided with the information and support they need to adopt healthy lifestyles.
酒精使用 Alcohol use
酒精使用是导致多种癌症的一项风险因素，包括口腔癌、咽癌、喉癌、食道癌、肝癌、结肠直肠癌和乳腺癌。罹患癌症的风险随着酒精摄入量的增加而增加。如果人们在大量饮酒的同时还大量吸烟，罹患多种癌症的风险会大幅提高。与酒精相关的特定癌症类型在男性和女性群体中有所不同，其主要原因是平均摄入水平的差异。例如，男性中因酒精引起的口腔癌和口咽癌占22%，而女性的相应负担则降至9%。这类性别差异还体现在食道癌和肝癌方面（Rehm et al.. 2004）。
Alcohol use is a risk factor for many cancer types including cancer of the oral cavity, pharynx, larynx, oesophagus, liver, colorectum and breast. Risk of cancer increases with the amount of alcohol consumed. The risk from heavy drinking for several cancer types (e.g. oral cavity, pharynx, larynx and oesophagus) substantially increases if the person is also a heavy smoker.
Attributable fractions vary between men and women for certain types of alcohol-related cancer, mainly because of differences in average levels of consumption. For example, 22% of mouth and oropharynx cancers in men are attributable to alcohol whereas in women the attributable burden drops to 9%. A similar sex difference exists for oesophageal and liver cancers (Rehm et al., 2004).
Rehm J et al. (2004). Alcohol use. In: Ezzati M et al., eds. Comparative quantification of health risks: global and regional burden of disease due to selected major risk factors. Geneva, World Health Organization: 959-1108.
感染 Infection
传染性病原体导致的癌症死亡在发展中世界占将近22%，而在工业化国家则占6%。乙型和丙型病毒性肝炎引起肝癌；人乳头状瘤病毒感染导致宫颈癌；幽门螺旋菌会增加患胃癌的风险。在某些国家，血吸虫等寄生虫感染增加了患膀胱癌的风险，而在其他一些国家，肝吸虫增加了胆管出现胆管癌的风险。预防措施包括疫苗接种及传染和感染的预防。
Infectious agents are responsible for almost 22% of cancer deaths in the developing world and 6% in industrialized countries. Viral hepatitis B and C cause cancer of the liver; human papilloma virus infection causes cervical cancer; the bacterium Helicobacter pylori increases the risk of stomach cancer. In some countries the parasitic infection schistosomiasis increases the risk of bladder cancer and in other countries the liver fluke increases the risk of cholangiocarcinoma of the bile ducts. Preventive measures include vaccination and prevention of infection and infestation.
环境污染 Environmental pollution
带有致癌化学物质的空气、水和土壤环境污染导致的癌症占癌症总病例的1–4%（IARC/WHO，2003）。饮用水或室内和周围空气污染可能会带来环境致癌化学物质暴露。在孟加拉国的砷污染地区， 5–10%的癌症死亡可归因于砷暴露（Smith，Lingas & Rahman，2000）。致癌物暴露还可因化学物质造成的食品污染而发生，如黄曲霉毒素或二恶英。燃煤造成的室内空气污染使肺癌发生风险加倍，尤其是对于不吸烟的妇女而言（Smith，Mehta & Feuz，2004）。全世界由于家用燃煤导致室内空气污染而造成的肺癌死亡约占肺癌死亡总数的1.5%。家庭用煤情况在亚洲尤为普遍。
Environmental pollution of air, water and soil with carcinogenic chemicals accounts for 1–4% of all cancers (IARC/WHO, 2003). Exposure to carcinogenic chemicals in the environment can occur through drinking water or pollution of indoor and ambient air.
In Bangladesh, 5–10% of all cancer deaths in an arsenic-contaminated region were attributable to arsenic exposure (Smith, Lingas & Rahman, 2000). Exposure to carcinogens also occurs via the contamination of food by chemicals, such as aflatoxins or dioxins. Indoor air pollution from coal fires doubles the risk of lung cancer, particularly among non-smoking women (Smith, Mehta & Feuz, 2004). Worldwide, indoor air pollution from domestic coal fires is responsible for approximately 1.5% of all lung cancer deaths. Coal use in households is particularly widespread in Asia.
IARC/WHO (2003). World cancer report. Lyon, IARC Press.
Smith AH, Lingas EO, Rahman M (2000). Contamination of drinking water by arsenic in Bangladesh: a public health emergency. Bulletin of the World Health Organization, 78: 1093-1103
Smith KR, Mehta S, Feuz M (2004). indoor air pollution from household use of solid fuels, In: Ezzati M et al., eds. Comparative quantification of health risks: global and regional burden of disease attributable to selected major risk factors. Geneva, World Health Organization: 1435-1493.
职业致癌物 Occupational carcinogens
在工作环境中，有40多种物质、混合物和暴露情况对人类有致癌性，它们被归类为职业致癌物（Siemiatycki et al., 2004）。职业致癌物与肺癌、膀胱癌、喉癌和皮肤癌、白血病及鼻咽癌之间的因果关系已有很好的文字记载。间皮瘤（肺或胸腔外膜上的癌症）在很大程度上与工作相关的石棉暴露有关。
More than 40 agents, mixtures and exposure circumstances in the working environment are carcinogenic to humans and are classified as occupational carcinogens (Siemiatycki et al., 2004). That occupational carcinogens are causally related to cancer of the lung, bladder, larynx and skin, leukaemia and nasopharyngeal cancer is well documented. Mesothelioma (cancer of the outer lining of the lung or chest cavity) is to a large extent caused by work-related exposure to asbestos.
Occupational cancers are concentrated among specific groups of the working population, for whom the risk of developing a particular form of cancer may be much higher than for the general population. About 20–30% of the male and 5–20% of the female working-age population (people aged 15–64 years) may have been exposed to lung carcinogens during their working lives, accounting for about 10% of lung cancers worldwide. About 2% of leukaemia cases worldwide are attributable to occupational exposures.
Siemiatycki J et al. (2004). Listing occupational carcinogens. Environmental Health Perspectives, 112:1447-1459.
辐射 Radiation
电离辐射对人具有致癌性。有关辐射风险的知识主要通过对日本原子弹幸存者的流行病学研究以及对医学和职业辐射暴露群体的研究得来。电离辐射可能诱发白血病和多种实体肿瘤，年轻时遭受暴露带来的风险更高。据估计，居住地土壤和建筑材料中的氡气暴露占肺癌总数的3%至14%，成为继烟草烟雾之后的第二大肺癌病因。家庭中的氡气浓度可以通过改善通风和密封地板及墙面得到改善。电离辐射是一种基本诊断和治疗工具。为确保使其益处大于潜在的辐射风险，应对放射性医学操作做出适当规定，并进行正确操作，以降低不必要的辐射剂量，尤其是儿童。
紫外线辐射，特别是太阳辐射，对人体具有致癌性，可导致所有主要类型的皮肤癌，如基底细胞癌（BCC）、鳞状细胞癌（SCC）和黑素瘤。2000年，全球共诊断出20多万例黑素瘤病例，还有6.5万例黑素瘤相关死亡。避免过度暴露，使用防晒霜和保护性服装都是有效的预防性措施。基于紫外线发射型肤色仪器与皮肤和眼黑素瘤之间的相关性，该设备现在也被列为对人类致癌类。
Ionizing radiation is carcinogenic to humans. Knowledge on radiation risk has been mainly acquired from epidemiological studies of the Japanese A-bomb survivors as well as from studies of medical and occupational radiation exposure cohorts. Ionizing radiation can induce leukaemia and a number of solid tumours, with higher risks at young age at exposure.
Residential exposure to radon gas from soil and building materials is estimated to cause between 3% and 14% of all lung cancers, making it the second cause of lung cancer after tobacco smoke. Radon levels in homes can be reduced by improving the ventilation and sealing floors and walls. Ionizing radiation is an essential diagnostic and therapeutic tool. To guarantee that benefits exceed potential radiation risks radiological medical procedures should be appropriately prescribed and properly performed, to reduce unnecessary radiation doses, particularly in children.
Ultraviolet (UV) radiation, and in particular solar radiation, is carcinogenic to humans, causing all major types of skin cancer, such as basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma. Globally in 2000, over 200 000 cases of melanoma were diagnosed and there were 65 000 melanoma-associated deaths. Avoiding excessive exposure, use of sunscreen and protective clothing are effective preventive measures. UV-emitting tanning devices are now also classified as carcinogenic to humans based on their association with skin and ocular melanoma cancers.
