There’s been a lot of press this last week about the reported breakthough in genome testing that will pinpoint clusters of imperfectly-copied genes that increase the risk of inheriting breast cancer. Much of the excitement is due to the fact that the technique can be equally well used in testing for other genetic combinations that increase the risk of developing cancers of all sorts, not just the breast tissue.

There’s no doubt that it is an exciting development indeed. There’s been plenty of hoopla, and the scientists who developed this will no doubt do very well from it, and so they should. However, I want to pinpoint one aspect that’s missing or at least glossed over in a lot of the coverage of the original Nature article detailing the new technique: inherited cancer vulnerability doesn’t explain most diagnosed cancers.

Contrast this fairly typical coverage from Business Weekly:

Two of the genetic regions they identified contain genes that are thought to increase breast cancer risk by about 20 per cent in women who carry one faulty copy of a gene and by between 40 and 60 per cent if they carry two faulty copies.

The lifetime risk for women who carry two faulty copies in either of these two genes would rise from one in 11 to around one in six or one in seven, respectively.

With this from Medical Laboratory World:

Breast cancer that is caused by inherited genetic faults is thought to account for around 5% to 10% of the 44,000 new cases diagnosed each year.

They’re both actually saying the same thing about the proportion of inherited gene factors leading to cancer, but one is using obfuscation to glide by it and the other is being clear about how inherited genetic faults are a minority of cancer cases.

Now obviously, if people with a genetic vulnerability know of it and are thus more aware of possible early symptoms and thus seek early treatment, this has the potential to save thousands of lives, or at least to prevent them from having to undergo radical surgery if their cancer can be treated less invasively and still be controlled. But what are the factors thought to be oncogenic amongst the 90-95% of breast cancer patients diagnosed each year who aren’t thought to have a particular genetic vulnerability?

Cancer arises from damaged DNA that leads cells to proliferate beyond normal rates/boundaries, and that DNA damage happens to our cells all the time. Most of the time our bodies’ DNA repair mechanisms prevent proliferation of the damage:

The DNA damage response is a routine event in the life of any cell. Stress caused by environmental factors such as exposure to ultraviolet light, ionizing radiation or other environmental phenomena can cause DNA to break apart or rearrange its nucleotide base pairs in unhealthy ways. If such mutations are left unchecked, they can accumulate over time and lead, ultimately, to cancer or diabetes.

At least part of the problem seems to be the overindulgences of affluence, as epidemiologists predict that Asia will have a surge in cancer cases over the next decades due to economic success leading to increased longevity and also “bad habits”:

Asia is bracing for a dramatic surge in cancer rates over the next decade as people in the developing world live longer and adopt bad Western habits that greatly increase the risk of the disease.

Smoking, drinking and eating unhealthy foods “” all linked to various cancers “” will combine with larger populations and fewer deaths from infectious diseases to drive Asian cancer rates up 60% by 2020, some experts predict.
[…]
“What happened in the Western world in the ’60s or ’70s will happen here in the next 10 to 20 years as life expectancy gets longer and we get better control on more common causes of deaths,” said Dr. Jatin P. Shah, a professor of surgery at Memorial Sloan-Kettering Cancer Center in New York, who attended a cancer conference last month in Singapore.

“The habit of alcohol consumption, smoking and dietary changes will increase the risk of Western world cancers to the Eastern world,” Shah said.

An estimated 40% of cancers worldwide can be prevented by exercise, eating healthy foods and not using tobacco, according to the World Health Organization.
[…]
Cancer deaths are slowly dropping in the United States, with slight declines recorded in 2003 and 2004. A decrease in smoking, coupled with early detection and better treatment of tumors is credited with the positive results “” the first U.S. decline in cancer deaths since 1930.

Smoking is on the rise in Asia, where it’s common to see people lighting up in airports, restaurants and even hospitals. Lung cancer makes up the bulk of all cases regionwide, followed by stomach and liver cancers. It also remains the biggest cancer killer worldwide.

Most of us know this, at least in broad outline, from the various health do’s and don’ts drummed into us over the years. But it’s worth noting just how stark the difference is between populations that don’t smoke/drink/over-eat crappy food, and those that do. It isn’t just inheritance that damages DNA and thus leaves it vulnerable to forming cancers, it’s what we do with our body every day.

So what are the other oncogenic factors? Obviously, there are known carcinogens such as radiation exposure and certain fairly rare chemicals that are generally only risk factors to people working in certain industries. But it isn’t only people exposed to these high risk factors that develop cancer, so what is damaging people’s DNA elsewhere?

It’s rarely discussed in the popular media, but the other factors of industrialised affluence that drive up cancer rates are the pollutants all around us, the toxins in our air, water and food due to industrial waste, pesticides, weedcontrol, fertilisers, and thousands of other substances that form the infrastructure of our mass-production economy.

On average, just one in 10 breast cancer cases is caused by genetic factors, asserts Breast Cancer Fund communications director Dana Oshiro.

“As an organization we focus specifically on environmental causes. We’re talking about chemicals and radiation,” Oshiro said.

Money raised from events such as “Climb Against the Odds” helps fund legislative efforts, public education and consumer outreach, Oshiro said.

According to the Breast Cancer Fund, only 10 percent of the 100,000 chemicals in use in the United States are safety-tested for consumers. Materials used in some shampoos, cosmetics and even baby bottles, among other consumer products, have been found to cause cancer in rats, and scientists suspect these same compounds may contribute to human cancer rates.

“Scientists increasingly believe that the environment and chemicals and radiation and different levels of exposure is something that actually affects your risk,” Oshiro said. “At this point it’s difficult to say breast cancer can be eradicated completely, but we’re looking at the environmental causes.”

In Australia the dreaded and derided nanny-statism has thankfully given us a few more protections with respect to safety-testing of consumer products than is present in the States, but the high level of chemical contamination of our daily spaces – home, office, bus, car – and also the effect of constant immersion in low-level electromagnetic radiation from our dazzling array of electronic tools and toys has not been studied as comprehensively as it could be in terms of the daily risk of DNA damage that lifestyle puts us in. There doesn’t appear to be the funding for it.

Now, I don’t have a lot of answers to offer here. Sure I can envision a clean-green-fuelled agrarian utopia, where self-sufficient communities would still produce a surplus that could drive a technologically innovative commercial sphere, and we’d all live cancer-free with our DNA copying itself normally every minute of every day. It’s a lovely dream. Should we all live in minimalist spaces with all the electric devices banished to one room in which our time is strictly rationed? What other sacrifices of modern conveniences will people be willing and able to make in order to minimise a hypothetical cancer risk, or even an actual measured and verified cancer risk sometime in future years? I’m well aware of the risks of modern industrialised environments to short term health, let alone long time health risks such as oncogenesis, yet I still live in the inner city. My lifestyle preferences for other reasons override what I know to be health risks, and I’m far from alone.

So, having nothing more practical to offer, I just say: don’t fall for the over-hype of this particular genetic discovery. It is a valuable innovation and will indeed save lives, but for the vast majority of cancer subjects it will make not a whit of difference. Sorry.

Categories: health, medicine