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  3. (1)Sometimes you can know too much. The aim of screening healthy people for cancer is to discover tumours when they are small an

(1)Sometimes you can know too much. The aim of screening healthy people for cancer is to discover tumours when they are small an

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问题     (1)Sometimes you can know too much. The aim of screening healthy people for cancer is to discover tumours when they are small and treatable. It sounds laudable and often it is. But it sometimes leads to unnecessary treatment The body has a battery of mechanisms for stopping small tumours from becoming large ones. Treating those that would have been suppressed anyway does no good and can often be harmful.
    (2)Take lung cancer. A report in this week’s Journal of the American Medical Association, by Peter Bach of the Memorial Sloan-Kettering Cancer Centre in New York and his colleagues, suggests that, despite much fanfare around the use of computed tomography(CT)to detect tumours in me lungs well before they cause symptoms, the test may not reduce the risk of dying from me disease at all—indeed, it may make things worse.
    (3)The story begins last year, when Claudia Henschke of Cornell University and her colleagues made headlines with a report mat patients whose lung cancer had been diagnosed early by CT screening had excellent long-term survival prospects. Her research suggested that 88% of patients could expect to be alive ten years after their diagnosis. Dr. Bach found similar results in a separate study. In his case, 94% of patients diagnosed with early-stage lung cancer were alive four years later.
    (4)Survival data alone, though, fail to answer a basic question: "compared with what?" People are bound to live longer after their diagnosis if mat diagnosis is made earlier. Early diagnosis is of little value unless it results in a better prognosis.
    (5)Dr. Bach, merefore, interrogated his data more thoroughly. He used statistical models based on results from studies of lung cancer that did not involve CT screening, to try to predict what would have happened to me individuals in his own study if they had not been part of mat study. The results were not encouraging.
    (6)Screening did, indeed, detect more tumours. Over me course of five years, 144 cases of lung cancer were picked up in a population of 3,200, compared with a predicted number of 44. Despite these early diagnoses, though, there was no reduction in the number of people who went on to develop advanced cancer, nor a significant drop in the number who died of me disease(38, compared with a prediction of 39). Considering mat early diagnosis prompted a tenfold increase in surgery aimed at removing the cancer(the predicted number of surgical interventions was 11; the actual number was 109), and that such surgery is unsafe—5% of patients die and another 20-40% suffer serious complications—the whole process seems to make things worse.
    (7)Dr. Bach’s conclusion is that many of me extra cancers picked up by CT screening would never have caused clinical disease, while the most aggressive tumours—those that cause most of the 160,000 lung-cancer deaths in America each year—grow too quickly to be found early, even with annual CT screening. The situation resembles prostate-cancer screening, which relies on a blood test for a molecule secreted by prostate tumours. In prostate screening, a lot of disease is identified, but mere is great doubt over me number of lives this saves. Dr. Bach’s research also resembles an earlier attempt to deal with lung cancer, in which researchers uncovered 20% more tumours in groups that underwent screening using chest X-rays than in those who did not. Then, too, the frequency of death from the disease did not differ between the two groups. Both Dr. Bach and Dr. Henschke had hoped that by using CT, which is better than X-rays at picking up small tumours in the lungs, they might have changed this outcome.
    (8)Dr. Bach was comparing data from screened people with a model of what would have happened to an unscreened group. The final word on CT screening for lung cancer will have to wait for the results of a proper experiment that compares screened and unscreened groups. These are expected in the next year or two. The omens, however, are bad. What you do know can hurt you.
According to Paragraph 7, prostate-cancer screening is similar to CT screening in that _____.
选项 A、both of mem are advanced medical apparatus
B、both of them are used for the treatment of cancer
C、neither significantly reduces the death rate of cancer patients
D、neither of them can identify tumours in the early stage
答案C
解析 第7段首句提到，侵袭性极强的肿瘤由于生长过快，即便每年用CT筛查也无法及早检出：接着第2句用resembles“类似于”一词表明前列腺癌也是这样，故可推断CT筛查和前列腺癌筛查都不能明显降低癌症病人的死亡率，C符合题意。前列腺癌筛查和CT筛查是两种检查方法，不是医疗仪器，故排除A：这两种检查方法都是用来发现、诊断肿瘤等的，而不是用于治疗癌症，故B错；该段首句是说the mostaggressive tumours难以及早查出，而D说的是tumours，语义范围不对，故也可排除。
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