Smoking may also activate some genes in a permanent, harmful way and turn off others that repair damaged DNA - which may explain the persistent risk of lung and other cancers among people who have quit. 'Fifty per cent of newly diagnosed lung cancer patients are former smokers,' say researchers from the British Columbia Cancer Research Centre in Vancouver, whose study found that although many genetic changes stop when a smoker quits, several genes stay turned on for years, including several not previously linked with smoking. Only about one-fifth of the genes in any cell are switched on at any given time, Reuters reports.

Illness can influence divorce

People with cervical or testicular cancer are more likely to get divorced than those without the disease, researchers from the Norwegian Cancer Registry have found in a study of 215,000 people. There was no such correlation for other forms of cancer, AP reports. Women with cervical cancer had a 40 per cent higher chance of getting divorced than similar women without the cancer; and men with testicular cancer were 20 per cent more likely to get divorced. Both cancers typically are diagnosed at younger ages than other cancers, when divorce rates tend to be higher anyway and sex is probably a more important factor in relationships, the researchers say.

Breast cancer on rise in Asia

Breast cancer is on the rise among Asian women - and attacking earlier than in the US and Europe. 'We are seeing younger women with breast cancer throughout the region,' says Louis Chow, head of Hong Kong's Organisation for Oncology and Translational Research. 'We are not even surprised to see those in their 30s.' Unlike in the west, the risk factors are not clear. Breast cancer cases among Hong Kong women aged 30 to 39 rose 43 per cent between 1978-82 and 1993-97, Reuters reports. The numbers rose to 63 per cent for those aged 40 to 49.