"I have great confident that by the end of the decade we'll know in vast detail how cancer cells arise," says microbiologist Robert Weinberg, an expert on cancer. "But," he cautions, "some people have the idea that once one understands the causes,the cure will rapidly follow. Consider Pasteur. He discovered the causes of many kinds of infections, but it was fifty or sixty years before cures were acailable."
This year,50% of 910,000 people who suffer from cancer will survive at least five years. In the year 2005, the National Cancer Institute estimates, that figure will be 75%. For some skin cancers, the five-year survival rate is as high as 90%. But other survival statistics are still discouraging—13% for loung cancer, and 2% for cancer of the pancreas.
With as many as 120 varieties in existence, discovering how cancer works is not easy. The researchers made great progress in the early 1970s, when they discover that oncogenes, which are cancer-causing genes, are inactive in normal cells. Anything from cosmic rays to radiation to diet may activate a dormant oncogene, but how remains unknown. If several oncogenes are driven into action, the cell, unable to turn them off, becomes cancerous.
The exact mechanisms involves are still mysterious, but the likelihood that many cancers are initiated at the level of genes suggests that we will never prevent all cancers. "Changes are a normal part of the evolutionary process," says oncologist William Haywar. Envionmental factors can never be totally eliminated; as
The prospects for cure, though still distant, are brighter.
"First, we need to understand how the normal cell controls itself. Second, we have to determine whether there are a limited number of genes in cells which are always responsible for at least part of the trouble. If we can understand how cancer works, we can counteract its action."
癌症治疗的前景
“我确信我们可以在这个年代末详细得了解癌症是如何滋生的”微生物学家，同时也是癌症专家罗伯特.文伯格如是说，“但是”，他提示说，“一些人认为一旦知道了它的成因，治疗方案就会马上产生。想想帕斯特，他发现了很多类型感染病的原因，但直到50年或60年后才找到治疗方法。”
今年，91万患者中有50%有5年存活率。国家癌症委员会估计到2005年这个数字会达到75%。对于一些皮肤癌，5年存活率可达到90%。但是对于其他存活数据统计结果仍不乐观——肺癌是13%， 胰腺癌仅为2%。
相关的确切过程是神秘的，但是很多癌症是从基因水平产生的这种可能是我们无法预防所有癌症。“变化是进化过程的正常组成部分，”肿瘤学家威廉姆.海耶华说。环境因素可能无法完全消除，海耶华指出，“我们不能准备组织宇宙射线的药物。”
癌症存在类型多达120种，揭示癌症如何作用并非易事。在20世纪70年代，研究者们取得了重大进步，他们发现肿瘤基因——一种引起癌变的基因，在正常的细胞中是非活动状态。从宇宙射线到日常饮食辐射的任何东西都可能激活沉寂中的肿瘤基因，但是如何激活还不为人知。如果若干肿瘤基因被激活，而细胞又无法灭活它们，就成为癌细胞。
治疗的前景，虽然还很遥远，但是还是光明的。
“首先，我们需要明白正常细胞是如何控制自己的。其次，我们必须确定细胞中是否存在一定的基因至少是引起问题的部分原因。如果我们能够知道癌症是如何作用的，我们就能中断它的进行。”