Screen Test
1. Every year millions of women are screened with X-rays to pick up signs of breast cancer. If this happens early enough, the disease can often be treated successfully. According to a survey (調(diào)查)published last year, 21 countries have screening programmes. Nine of them, including Australia, Canada, the US and Spain, screen women under 50.
2. But the medical benefits of screening these younger women are controversial(有爭(zhēng)議的), partly because the radiation(輻射) brings a small risk of inducing cancer. Also, younger women must be given higher doses of X-rays because their breast tissue(組織) is denser.
3. Researchers at the Polytechnic University1 of Valencia analysed the effect of screening more than 160,000 women at 11 local clinics. After estimating the women’s cumulative dose of radiation, they used two models to calculate the number of extra cancers this would cause.
4. The mathematical model recommended by Britain’s National Radiological Protection Board (NRPB) predicted that the screening programme would cause 36 cancers per 100,000 women, 18 of them fatal. The model preferred by the UN Scientific Committee on the Effects of Atomic Radiation led to a lower figure of 20 cancers.
5. The researchers argue that the level of radiation-induced cancers is “not very significant” compared to the far larger number of cancers that are discovered and treated. The Valencia programme, they say, detects between 300 and 450 cases of breast cancer in every 100,000 women screened.
6. But they point out that the risk of women contracting cancer from radiation could be reduced by between 40 and 80 percent if screening began at 50 instead of 45, because they would be exposed to less radiation. The results of their study, they suggest, could help “optimize the technique” for breast cancer screening.
7. “There is a trade-off(平衡) between the diagnostic(診斷的，判斷的) benefits of breast screening and its risks,” admits Michael Clark of the NRPB. But he warns that the study should be interpreted with caution. “On the basis of the current (目前的)data, for every 10 cancers successfully detected and prevented there is a risk of causing one later in life. That’s why radiation exposure should be minimized in any screening programme.”
每年上百萬的女性都做X射線透視，檢查是否有乳腺癌跡象。如果檢查得足夠早，疾病就可 以被成功地治療。根據(jù)去年公布的一項(xiàng)調(diào)查，21個(gè)國(guó)家有透視計(jì)劃。其中9個(gè)國(guó)家，包括澳大利 亞、加拿大、美國(guó)和西班牙為50歲以下女性進(jìn)行透視。
但是，用X射線檢查年輕女性，就醫(yī)學(xué)上的好處而論，是有爭(zhēng)議的，部分原因是輻射有誘發(fā) 癌癥的小小的危險(xiǎn)。另外，年輕女人*組織緊密，給予的X射線的劑量要多一些。
Valencia理工大學(xué)的研究人員分析了 11個(gè)社區(qū)診所用X射線檢查16萬以上女性的結(jié)果。估 測(cè)了女性的輻射累積劑量之后，他們用兩種模型計(jì)算由此導(dǎo)致額外癌癥數(shù)量。
英國(guó)國(guó)家輻射保護(hù)委員會(huì)推薦的數(shù)學(xué)模型預(yù)言，透視計(jì)劃會(huì)導(dǎo)致每10萬個(gè)女性中有36人患 上癌癥，18人致死。聯(lián)合國(guó)原子輻射影響科學(xué)委員會(huì)首選的模型得出了一個(gè)較低的數(shù)字^20人 患上癌癥。
研究人員爭(zhēng)辯說，與發(fā)現(xiàn)后接受治療的癌癥數(shù)字相比，由輻射誘發(fā)癌癥的數(shù)字是很小的。他 們說，Valencia計(jì)劃在每10萬接受透視的婦女中發(fā)現(xiàn)300到450個(gè)乳腺癌病例。
但是他們指出如果X射線檢查從50歲而不是45歲時(shí)開始，會(huì)使婦女由于輻射而患癌的危險(xiǎn) 減少40%到80% ,因?yàn)樗齻兛梢越邮芨俚妮椛�。他們暗示說，他們研究的結(jié)果有助于使乳腺癌 透視的技術(shù)更加完善。
英國(guó)國(guó)家輻射保護(hù)委員會(huì)的Michael Clark承認(rèn)“在胸透的診斷益處和危險(xiǎn)之間有一個(gè)平衡”。 但是他警告說應(yīng)該謹(jǐn)慎地解釋此項(xiàng)研究�！盎谀壳暗臄�(shù)據(jù)，每成功地發(fā)現(xiàn)10例癌癥就有可能導(dǎo) 致今后出現(xiàn)一例癌癥。這就是為什么在所有的透視計(jì)劃中，輻射應(yīng)該減少到小的原因�！�
