The hype and hysteria surrounding genetic science shows no signs of abating. And in the wake of the human genome project, the excited predictions have come thick and fast.
Deciphering the genetic code, it's been claimed, will revolutionise medicine. Cures will be tailored to a patient's unique biological make up. Babies will be screened to reveal what diseases they will catch aged 75. Gene therapy will repair diseased bodies from within.
The government has caught the gene bug too. This summer, the health secretary, John Reid, published a white paper on genetic research in the NHS. Our Inheritance, Our Future promised that Britain would lead the world in gene research and development. He promised an additional £50 million for gene science and asked the Human Genetics Commission to investigate the ethics of mass DNA screening for all newborn babies.
The potential for genetic science in cancer is enormous. Cancer is a combination of genetics and lifestyle factors. It occurs when environmental triggers damage a cell's DNA, causing it to divide uncontrollably.
But the role of inheritance in cancer is often massively overstated. A study of 90,000 Scandinavian twins three years ago concluded that lifestyle and environmental factors such as smoking, diet and exercise, were far more important than genes in determining cancer risk. Even an identical twin has only a 10 per cent chance of developing the same cancer as his or her sibling. The throw of the genetic dice determines susceptibility to cancer, but lifestyle usually determines whether we will get the disease.
It's not just the lifestyle-gene balance that gets distorted. After the first draft of the human genome was published three years ago, the public could be forgiven for thinking that there was nothing left to discover about our genetic heritage
In fact, a key finding from the genome project was how few genes there are in the human body ? somewhere in the region of 35,000. Compare that to the miniscule nematode worm which has just under 20,000.
The complexity of humans has little to do with the number of genes, but how the proteins they encode for interact in the body. The whole is greater than the sum of the parts.
The attention of genetic researchers is now turning to "proteomics" ? the study of that complexity.
In November 2003, scientists completed the first protein map of an organism, the fruit fly. The map showed 20,000 interactions between the fly's 7,000 proteins. Putting together a protein map of people is a major undertaking ? and will take many more years. But it's from these protein maps that the medical benefits will eventually pour.
Meanwhile, another branch of genetics is starting to explain exactly what those 30,000 human genes do.
RNA interference is thought by many to be the most promising breakthrough of the last 10 years. RNAi works by silencing genes in a cell one by one ? allowing scientists to find out exactly what each one does and how it contributes to cancer.
Cancer Research UK and the Netherlands Cancer Institute are spending £500,000 analysing the first 8,000 human genes using RNAi. Eventually the charities will have a library of the whole genome, pinpointing which genes are involved in which cancers.
As the results from these new approaches to disease emerge, society is going to have to get to grips with the implications, particularly in respect to gene testing.
Gene testing raises a host of ethical problems. Few cancers are caused by single gene defects (the hereditary breast cancer genes BRCA 1 and 2 are exceptions) but the interplay of several genes. So rather than give a prognosis, a gene test for cancer will provide a risk assessment for an individual.
Test results should, in theory, give people a chance to reduce their risks. That could include quitting smoking, eating more healthily and taking more exercise.
But will a test actually make a difference? Smokers already know their addiction is likely to kill them, but continue to smoke anyway.
Gene testing also raises concerns that employers will use results to discriminate against staff. And those born with the wrong genes may struggle to get insurance. Widespread screening will also need a massive expansion in NHS counselling services to put the result into a meaningful context for patients.
A less controversial use of testing is in the improved targeting of medicines. Gene chips, or microarrays, are being developed that can reveal how someone will respond to chemotherapy and radiation therapy.
Another much-hyped branch of medicine is gene therapy. The approach is still experimental, but researchers have successfully used gene therapy to weaken cancer cell defences against radiation and drug treatment, and to target tumours.
The white paper pledged an extra £3 million for 4,000 single gene disorders and an additional £2.5 million for cystic fibrosis. Another £4 million will go on the vectors ? usually the modified viruses ? that transport genes within the body.
That sounds a lot, but it's a drop in the gene pool. Dr Adrian Thrasher of the Institute of Child Health, London, is one of the few researchers to have success with gene therapy in Britain. His team have used a form of gene therapy to treat a handful of "bubble babies", born without healthy immune systems, at Great Ormond Street Hospital. This one treatment cost around £1 million to develop, while a single child's treatment costs around £100,000. Mr Reid's money for gene therapy is unlikely to go very far.
Away from the pure genetic research, more traditional pharmaceutical science has been busy developing some exciting new drugs. One of the most interesting is Glivec, the leukaemia treatment described as the first cancer drug to be put together piece by piece from first principles, rather than by trail and error. It works by precisely targeting the molecules thought to cause the cancer.
Two promising drugs could soon be improving survival rates for breast cancer. Doctors currently only give tamoxifen ? the gold standard drug ? for five years after surgery. The tests suggest that another drug lestrozole, which has just completed a major clinical trial, can be given for another five after that ? halving the rates of recurrence. Another new contender, anastrozole appears to be even better than tamoxifen in treating breast cancer in post menopausal women.
Older drugs are also showing promise. Aspirin ? the wonder drug for blood thinning and headaches ? may also have a major role in cancers, as might the painkilling Cox2 inhibitors.
But despite all these wonder drugs ? and the breakthroughs in surgery and radiotherapy ? most lives will not be saved by scientists, researchers and doctors coming up with cunning new treatments.
They will be saved, as they have been for the past few decades, by prevention and early detection.
It's not sexy or glamorous. And it doesn't win Nobel prizes. But around a third of cancers could be avoided if people gave up smoking, and up to a third if they improved their diets.
Yet this stark fact is not reflected in the headlines and, crucially, in the funding decisions. Despite its potential to save thousands of lives, spending on cancer prevention accounts for less than seven per cent of all spending on cancer research. When it comes to money, the hype talks.
