Cancer: the good news
It's the most feared disease, but great leaps forward in detection and treatment mean more of us are surviving it.
Tuesday 02 August 2011
Judging by a report released earlier this month, it looks like we're losing the war on cancer. The report, by Macmillan Cancer Support, revealed that four in 10 people in the UK will get the disease at some point in their lives. The health charity adds that this figure has risen significantly in the past decade and poses a "massive challenge" for the NHS.
So far, so grim. But a new book, Why Millions Survive Cancer: The Successes of Science, paints a far more optimistic picture. Its author, Dr Lauren Pecorino, principal lecturer in cancer biology at the University of Greenwich and a Fellow of the Royal Society of Medicine, lays bare the science behind our battle with this most notorious of diseases. "I thought it was time to report our progress on cancer for a change," she says.
There are currently 28 million cancer survivors worldwide. Although some forms of cancer are on the increase because of factors such as rising obesity levels, the main reason more of us will get cancer is because we are living longer. Cancer is, primarily, a disease of old age. Ironically, it's our successes in eradicating lethal diseases such as smallpox, aligned to advances in medical science, that keep many in the industrialised countries alive long enough to get cancer.
Pecorino explains the great leaps forward currently being made by researchers and clinicians across the globe in cancer detection and treatment, while lauding the unprecedented access to information made possible by the internet. Armed with this information – and an increasingly sophisticated knowledge of the importance of our lifestyle choices – we now have the power to drastically reduce our risk of contracting many of the most lethal cancers.
Why can't we cure cancer?
For two reasons: because there's actually no such thing as "cancer". Instead, it's a collective term for many different diseases – of the skin, breast, lung, colon, brain, and so on. So it's impossible to find a single cure, especially as each of these types of cancer may be caused by a different carcinogen, such as tobacco smoke, or ultra-violet radiation for skin cancer.
So it's extremely unlikely that there will ever be a single "magic bullet" to cure all cases. That said, let's examine the good news in terms of prevention and treatment.
Food, glorious food
Every day brings a new "Miracle Food Cures Cancer!" headline in the media, often linked to spurious claims backed up by poor-quality research. Happily, says Pecorino, a 2007 report by the World Cancer Research Fund and American Institute for Cancer Research, Food Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective, cuts through the nonsense.
Pecorino, who draws from the report in her book, says of its 10 main recommendations, avoiding weight gain is among the most important: "One of the best things you can do to minimise cancer risk is to maintain a healthy body weight throughout your life. There is convincing evidence that excess body fat is a risk factor for several cancers, because it increases the production of oestrogen and causes chronic inflammation – both of which are linked with various forms of cancer."
It's also key to eat a "rainbow" diet of fruit and veg, varying the colour/type of produce as much as possible, but not only for the oft-repeated reasons. "One exciting discovery... is that there are components in fruit and vegetables that can actually turn genes on and off. Some of those genes are key to processes that protect us against cancer, such as DNA repair or detoxing – turning on enzymes that help us excrete carcinogens more rapidly," says Pecorino.
She adds that, along with the gene-regulating qualities of vitamins A and D, our knowledge about which other foods have similar powers is "set to explode in the next few years".
Other lifestyle choices are equally important to diet. For example, physical activity has many benefits apart from maintaining a healthy body weight. Evidence increasingly shows that it boosts the immune system and reduces the likelihood of colon cancer.
Also, if you smoke, you are inhaling 81 different carcinogens with every puff. These chemicals, explains Pecorino, "stick to your DNA and mask the genetic code, so you produce faulty proteins".
She explains that the genetic code that governs the actions of our bodies' cell is made up of four different chemicals. The code is a set of instructions to make proteins, which carry out all of the basic functions in our body. When the code can't be read, because the carcinogens have "masked" it, abnormal proteins are made, which cause abnormal growth in the cell – and abnormal growth causes cancer.
Excessive consumption of alcohol causes cancer in roughly the same way as smoking. "In the body, alcohol is metabolized to acetaldehyde, a carcinogen that causes DNA damage and therefore cancer," says Pecorino. "There is convincing evidence that alcohol plays a role in increased risk of cancer of the mouth, oesophagus and breast and probable evidence for increased risk of liver cancer."
The good news is that, as with diet, smoking and physical activity, we have the power to drink sensibly and reduce our likelihood of getting cancer.
Screening and treatment
Detection has been a controversial area in recent years, particularly in breast cancer. Some experts have argued that the tendency for mammograms to produce "false positives" means that women have been subjected to unnecessary – and stressful/invasive – treatment. But Pecorino says: "For breast cancer, the statistics show there has been a decrease of 35 per cent in mortality due to screening. The benefits far outweigh the risks."
This view was backed up by a 2010 study of 80,000 women by experts from the Woolfson Institute of Preventive Medicine at Barts and the London School of Medicine and Dentistry. It suggests that screening saves the lives of two women for every one who may have unneccessary treatment.
Prostate cancer is more of a grey area – because the standard PSA test is not perfect – but researchers are developing better tests. Cervical cancer screening is more clear-cut: "As recently as the 1940s cervical cancer was a major cause of death for women in their childbearing years," says Pecorino. "Now 75 per cent of cases are prevented through screening in the UK and US."
For cancer sufferers, the three-stage treatment model of surgery, radiotherapy and chemotherapy has saved millions of lives. And these treatments are constantly being refined and improved, meaning greater success rates and fewer side effects.
But the really exciting area is genomics, or "personalised medicine". Pecorino explains: "Learning about the genome of a tumour is very important in guiding treatment. Everyone's tumour DNA is different, because it's a record of the exposure to carcinogens over time. So learning about which mutations are specific to that tumour helps us choose a better treatment."
To take a recent example, the breast cancer drug Herceptin only works in tumours with an increase in the HER2 protein. If the tumour doesn't have that genetic defect the drugs won't work. So as scientists better understand the genetics of cancer, their treatments will be increasingly effective.
Dr Julie Sharp, Cancer Research UK's senior science information manager, says that although good progress is being made, there is better news with some cancers than others. "We are seeing great improvement in children's cancers, because 75 per cent of children now survive. The same goes for breast and bowel cancer, and some of the leukemias and lymphomas. But we would like to see that progress in things like pancreatic, oesophageal and lung cancers, which are really hard to detect and treat," she says.
Overall then, encouraging advances are being made in the war on cancer. Balancing out the risks associated with an ageing, increasingly overweight global population, are the giant strides in screening, treatment and prevention. And as our knowledge deepens over the coming years, the power to avoid cancer will be in our hands.
'Why Millions Survive Cancer: the Successes of Science', by Lauren Pecorino (Oxford University Press, £16.99)
How to lower your cancer risk
* Be as lean as possible without becoming underweight.
* Be physically active for at least 30 minutes every day.
* Avoid sugary drinks and limit consumption of energy-dense foods that are high in added sugar, low in fibre or high in fat.
* Eat a variety of vegetables, fruits, wholegrains and pulses such as beans.
* Limit consumption of red meat and avoid processed meats.
* Limit alcoholic drinks to two for men and one for women per day.
* Limit consumption of salty foods and foods processed with salt (sodium).
* Don't use supplements to protect against cancer.
* If possible, mothers should breastfeed exclusively for up to six months and then add other liquids and foods.
* And, always remember, do not smoke tobacco.
(Adapted from the 2007 WCRF/AICR report, Food Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective)
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