The detection of cancer at an early stage in its development can be life-saving. With research efforts under way to find better methods to detect minuscule tumours, Laura Spinney finds out how near some of these cancer'biomarkers'are to the clinic. When it comes to halting cancer, nobody disputes the value of early detection. Dr George Papanico-laou's smear test, which measures changes in the cervical lining, is a testament to the importance of screening. Since 1950, when it was introduced, the Pap smear has reduced mortality due to cervical cancer by 70% in developed countries. About half of lung-cancer patients whose cancer is caught while it is still restricted to the lung survive. Nearly all of those diagnosed after it has spread die. (See graphic, opposite.)
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