The World Health Organisation's World Cancer Report says that if no preventive measures are taken increases of this order are inevitable because they stem from habits - such as smoking - that are already established. However, much can be done to slow the increase, Bernard Stewart, an Australian cancer specialist and co-author, said.

"Tobacco is the major preventable cause of cancer," he said. "But in developed countries diet, alcohol, a lack of exercise and the fact that we still don't eat five portions of fruit and vegetables a day are contributory factors.

Professor Stewart cited the cases of Finland and California. In Finland a programme of tobacco control, public education and dietary advice had seen lung cancer rates tumbling.

In California, the most anti-smoking state in America, lung cancer rates in women were falling. Everywhere else in the US they were rising.

到2020年，全世界癌症的发病率有可能增加50个百分点，每年可能将出现1500万新病例。

世界健康组织全球癌症报告指出，如果不采取积极的预防措施，这样的趋势将无法避免。因为这是从已经形成的生活习惯--例如抽烟--滋生出来的。尽管如此，该报告作者之一，澳大利亚癌症专家伯纳德·斯图尔德表示，还是有许多手段可以遏制这一增长趋势。

他说："烟草是引起癌症的主要罪源，因此预防也应该以烟草为主。但在发达国家，人们饮酒过多，缺乏运动，每天摄入的水果蔬菜低于摄入食物总量的5%。这些也都容易引发癌症。"

斯图尔德教授举了芬兰和加利福尼亚的例子来说明烟草的危害。芬兰实施了一项控制烟草的计划，包括进行公众教育和饮食建议，成效显著，肺癌患病率持续下降。

而加利福尼亚则是美国反烟草呼声最高的一个州。当其他州的女性肺癌得病率都在上升的时候，该州的这一数据却呈下降趋势。