The results of a major new study into the causes of cancer were published in the New England Journal of Medicine last week. A team of researchers based at the Karolinska Institute, Sweden, studied 44,788 sets of twins living in Sweden, Denmark and Finland to assess their lifetime risk of 28 different types of cancer.
The scientists found that overall, the chances that identical twins will develop the same type of cancer are less than 15 per cent. The study revealed that in three common types of cancer - prostate, colorectal and breast - susceptibility genes may play a greater role than previously thought. But even so, the vast majority of cancers are caused by environmental factors, rather than inherited genetic changes. If identical twins, who share their entire genetic make-up, have less than a 15 per cent chance of developing the same type of cancer, then relatives who share fewer genes are even less likely to do so.
Dr Tim Key, senior scientist at the Imperial Cancer Research Fund, Oxford said the study showed the dangers of fatalism among relatives of cancer victims. 'Even if you have a family history, you still probably won't get [the same type of] cancer, and what you do with your life is much more important' he said. He added that the number one factor was smoking, which accounts for 35 per cent of all cancers, and number two is thought to be diet, which accounts for 30 per cent.
Professor Gordon McVie, of the Cancer Research Campaign, said that the findings were interesting, but didn't alter the fact that cancer was ultimately a genetic disease. 'How you get to the genetic accident is still in question' he added.