练习：2009年卫生类ab级概括大意与完成句子
cancer癌症
1 cancer癌症 is a group of一组一群 many related相关的 diseases疾病 that begin in 开始，始于cells细胞, the body's basic基本的 building blocks.生命控制中心 the body is made up of many types of cells. 2normally,通常地 cells grow生长 and divide 分裂to produce产生 more cells as当---的时候 they are needed to keep the body healthy. 保持身体健康sometimes, this orderly process goes wrong. 3new cells form形成 when the body does not need them, and old cells do not die when they should. the extra cells form a mass of tissue called a growth or tumor. benign (良性的) tumors are not cancer. they can often be removed and, in most cases, they do not come back. malignant (恶性的) tumors are cancer. cells in malignant tumors are abnormal and divide without control or order.
4 scientists have learned that cancer is caused by 被---引起changes 改变变化in genes基因 that normally control 控制the growth生长 and death 死亡of cells. 5 certain 某种lifestyle生活方式 and environmental 环境factors因素can change some normal正常的 genes into 把---变成----genes that allow允许 the growth of cancer. 6 many gene changes that lead to 导致cancer are the result of tobacco 烟草use使用, diet饮食, exposure暴露 to ultraviolet [,ʌltrə'vaiələt]紫外线的radiation辐射 from the sun, or exposure to carcinogens [kɑ:'sinədʒən]（致癌物） in the workplace or in the environment.外界 some gene alterations are inherited.
cancer treatment can include surgery, radiation therapy, chemotherapy (化疗), hormone therapy, and biological therapy. the doctor may use one method or a combination of methods, depending on the type and location of the cancer, whether the disease has spread, the patient's age and general health, and other factors. 7 because treatment 治疗for cancer can also damage毁坏 healthy健康的 cells and tissues组织, it often causes side effects.副作用 patients and doctors generally discuss the treatment options, weighing the likely benefits of killing cancer cells and the risks of possible side effects.
having cancer does not always mean having pain. 8 whether a patient has pain may depend on 取决于the type类型 of cancer, the extent 程度of the disease, and the patient's tolerance忍受 for pain. 9most pain occurs when the cancer grows and presses压迫 against bones骨头, organs器官, or nerves神经. pain may also be a side effect of treatment. however, pain can generally be relieved or reduced with prescription medicines or over-the-counter drugs recommended by the doctor.