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您周围的环境可能含有会导致患癌风险增加的有害化学物质。即使您不吸烟，但如果您前往有人吸烟的地方或是与吸烟者同住，您也可能会吸入二手烟。家里或工作场所的化学物质（如石棉和苯）也会增加患癌的风险。

The central role of DNA injury and epigenetic defects in DNA repair service genes in carcinogenesis The classical view of cancer is really a set of conditions driven by progressive genetic abnormalities which include mutations in tumor-suppressor genes and oncogenes, and in chromosomal abnormalities. A role for epigenetic alterations was identified inside the early 21st century.[103]

The afflicted genes are divided into two wide groups. Oncogenes are genes that market mobile expansion and copy. Tumor suppressor genes are genes that inhibit cell division and survival. Malignant transformation can come about throughout the formation of novel oncogenes, the inappropriate over-expression of typical oncogenes, or from the beneath-expression or disabling of tumor suppressor genes.

[188] The efficiency of chemotherapy is often minimal by its toxicity to other tissues in the body. Even though chemotherapy doesn't give a lasting treatment, it could be valuable to reduce indications for instance pain or to decrease the sizing of an inoperable tumor during the hope that medical procedures will turn out to be doable in the future.[citation essential]

例如，如果您遗传了一种使您易患癌症的基因突变，并不意味着您一定会患癌症。可能需要有一个或多个其他基因突变才会引起癌症。当您接触某种致癌物质时，您的遗传基因突变可能使您比其他人更容易患癌症。

用醫學影像技術檢測癌症，也遭遇類似問題。這些醫學影像檢測技術都是成本相當高且耗費時間。由於偵測的靈敏度極高，常發現細胞病變（英语：incidentaloma），這樣的腫瘤也可以被認為惡性，而進行具有潛在危險性的治療方法。

不受限制的生長（不死，由於有大量端粒酶，細胞不受到細胞凋亡機制的調控）

减少接触室外和室内空气污染，包括氡（一种由铀的自然衰变产生的放射性气体，可能在建筑物中，住宅、学校和工作场所积累）。

知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。

准确诊断癌症对采取适当有效的治疗措施必不可少，因为每种癌症类型都需要特定的治疗方案。治疗通常包括手术、放疗和/或全身性治疗（化疗、激素治疗、靶向生物治疗）。适当选择治疗方案既要考虑癌症又要考虑接受治疗的个体情况。在限定时间内完成治疗方案对于实现预期的治疗效果很重要。

The Dutch professor 癌症 Francois de la Boe Sylvius, a follower of Descartes, believed that all ailment was the result of chemical processes Which acidic lymph fluid was the reason for cancer. His modern Nicolaes Tulp believed that cancer was a poison that slowly but surely spreads and concluded that it was contagious.[230]

某些癌症的成長會受某些荷爾蒙的增加或減少而抑制。對荷爾蒙敏感的腫瘤常見的例子有乳癌和前列腺癌，減低或增加體內雌激素或雄激素往往可用來做為補充治療的一種。

While epigenetic alterations are located in cancers, the epigenetic alterations in DNA mend genes, leading to reduced expression of DNA maintenance proteins, can be of certain great importance.