It has taken me six months to be able to say "I have lung cancer" with any ease. It's not just the grim prognosis that makes the words stick in the mouth, it's the image that troubles me. Lung cancer is a disease of elderly male barflies with fags dangling from their lips, isn't it? So how can I - female, fittish and in my fifties - have it?
All too easily, it transpires. That Andy Capp stereotype is way out of date. Between 1975 and 2007, when men gave up smoking and women took it up, the number of men diagnosed with lung cancer dropped by 47 per cent in the UK while the figure for women grew by 65 per cent. If trends continue, women will soon overtake men.

Cancer is also being discovered in ever-younger patients. "My youngest is 26," says Mary O'Brien, head of the lung unit at the Royal Marsden Hospital. "He has been smoking cannabis, which seems to carry high risk because it is smoked with loose tobacco, no filter, and the smoke is held in the lungs for a long time."

Now that I've joined the club of the 39,000 unfortunates in the UK diagnosed each year, I discover that many of my fellow members are even further from the lung cancer stereotype. Among those I've come across are a mother in her thirties, a doctor in his twenties, a student diagnosed when aged only 19 and a woman in her early fifties with a family history of lung problems. None of them has ever smoked.

Most of us have, of course: smoking is a factor in 80 to 90 per cent of lung cancers. The smoking can have been long ago and not ever have been ever a serious addiction - I, for one, didn't ever graduate from packs of 10. None the less, to outsiders we are a bunch of suicidal idiots, a judgment that makes some of my fellow travellers so coy that they lie to strangers. "If anyone asks about the scar on my back, I say it's a shark bite," says a woman in her thirties operated on for lung cancer.

Image matters for a number of reasons. It has prevented lung cancer from attracting anything like its fair share of research funds: although it's the leading cause of cancer deaths in both men and women, it receives just 4 per cent of available funding. The inaccurate image has also meant that coughers and wheezers don't go to the doctor about their symptoms, because people like them don't get cancers, do they? Perhaps most important of all, the embarrassment factor leads to a widespread ignorance of what constitutes risky behaviour.

Everyone knows, of course, that smoking can lead to lung cancer. "Smoking kills" is plastered on every packet of cigarettes, yet 10 million adults in Britain continue to smoke. Do the young women I have just observed sitting outside a cafe, having coffee and a smoke instead of lunch, know that low-tar cigarettes are as carcinogenic as stronger ones - especially if they put their fingers over the holes in the filter and inhale deeply? Do they realise that it is a myth that smoking helps you lose weight? Or that it's not safe to gamble on giving up before you hit 40?

"Cancer can get you 20 or 30 years down the line," says Professor Siow-Ming Lee, a consultant oncologist at University College Hospital, London. When, in 2005, Deborah Hutton, the super-fit, yoga-loving health editor of Vogue was diagnosed with a type of lung cancer known as adenocarcinoma, she hadn't smoked for more than 20 years. When she died seven months later, she left money for a foundation dedicated to encouraging young people not to smoke.

It's uphill work. At present, a third of under-18s smoke. Astonishingly, the habit is not seen as sad and passe, but cool and rebellious, just as it was when I was young. Half of those smokers will carry on for 15 or 20 years, and those most at risk of developing cancer will be the girls. "It's partly that they start smoking earlier," says Lee. Aged 13, they are better than boys at persuading shopkeepers that they are 18. "Women also appear to have less DNA repair capacity, so they are more susceptible to lung cancer than men."
Women do, however, respond better to chemotherapy and survive longer than men. Why this might be - hormones? - remains a matter of conjecture. Understanding will lead to better drug treatments, but if the lung-cancer incidence and mortality figures are to fall, for both men and women, other changes are needed, too.

First, teenagers must be discouraged from experimenting with cigarettes: anyone who gets to 21 without smoking is very unlikely to start. Second, those who are hooked need to be helped to quit. And, third, the unlucky minority who will develop cancer or already has it, needs to be identified when the disease is preventable or curable.

None of these aspects of cancer is commercially attractive. But, fortunately, cancer prevention receives funding from Cancer Research UK. As well as working with scientists, such as Prof Lee, who are breaking new ground in relation to treatments, the charity also funds Prof Gerard Hastings, director of the Centre for Tobacco Control Research.

"In Western Australia, only 5 per cent of young people smoke," says Hastings. "Our figures could be as low, but we need more government action. The plans for putting cigarettes out of sight in shops seems to have stalled. We also need legislation over plain packaging. Since the ban on tobacco advertising, manufacturers have poured money into pack-design - creating packs that open in different ways or fit into a purse - in an attempt to make nasty chemicals appear aspirational and fashionable."

Ideally, he would like to see cigarette companies taken into public ownership to remove the incentive to sell. With the Government receiving pounds 10?billion in tax revenues from tobacco, that may not happen soon. In the meantime, how can parents stop their children smoking, a subject close to my heart since my 21 year-old is hooked?

'Taking the moral high ground doesn't work," says Hastings. "Talk about the way tobacco companies exploit people instead. The Truth campaign in America used shock tactics - one day they delivered what looked like 1,200 body-bags to Philip Morris's head office - and was very effective." In the long term, such an approach should work. Meanwhile, there are millions of current and former smokers at risk of developing cancer.

Only 10 per cent of lung cancers are presently diagnosed early enough for a cure to be possible. There could be more if there was a screening programme. While drug companies don't see much profit in testing kits that have to be produced as cheaply as possible, charities are again leading the way.

The preliminary results of a screening campaign in the US that targeted heavy smokers have shown a 20 per cent drop in mortality. Now, work is under way to develop breath, blood or urine tests that could be used on a broader scale. But we are not there yet.

Seeing those young people having a carefree cigarette for lunch, I want to rush in, and beg them to stub out their fags. It would be a dramatic gesture, but pointless. Instead, we can help them avoid paying a high price for their habit.

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