Half Of U.S. Cancer Cases Are Preventable, Study Shows

How Many Cancers Could Be Prevented?

More than half a million people died from cancer in the U.S. in 2011. We have many astounding advances in medicine to thank for that number not being higher. But that grim figure could also be a lot lower even without a breakthrough drug for breast or lung cancer.

In fact, more than 280,000 of those lives could have been spared by preventing the disease in the first place—all via behavioral and research changes based on scientific discoveries that have been made already, according to a new review article published online March 28 in Science Translational Medicine. This statistic is not new, the researchers pointed out, but quibbling over details of exactly how many cases of—or deaths from—each form of cancer are due to preventable risk factors, the researchers noted, has delayed investment in mitigating the risks that researchers already know about, the authors argued.

“We actually have an enormous amount of data about the causes and preventability of cancer,” Graham Colditz, a professor at the Washington University School of Medicine in St. Louis and co-author of the new study, said in a prepared statement. “It’s time we made an investment in implementing what we know.”

Scientists know, for instance, that more exercise and less alcohol intake can lower the risk for breast cancer and that quitting smoking drastically reduces the risk for lung cancer. We also know that vaccines for HPV and hepatitis can reduce liver and cervical cancers by more than half and that aspirin can reduce overall cancer death by some 20 percent. Getting these interventions to the right people, however, is easier said than done.

“The obstacles to these efforts are societal and arise from the organization of institutions, including academia, and in the habits of daily life,” the researchers wrote.

And habits can be hard to break, especially the biggest cancer-causing habit of all: smoking. Without smoking, at least 75 percent of all lung cancer cases in the U.S. could be avoided, they noted.

Research, too, needs to change the ways it gets things done. With the lion’s share of funding for cancer research allocated to seeking new treatments, the science of prevention can get short shrift—in funding and in academic esteem. Although much progress has been made in developing treatments to extend the lives of those who already have specific kinds of cancer, the researchers suggested that “behavioral interventions, such as smoking cessation or promotion of physical activity can diminish incidence and mortality of many types of cancer and other chronic diseases while at the same time improving quality of life.”

Colditz and his colleagues suggested that professional prestige be bestowed not just on basic biological discoveries, but also on applied medicine and those who discover how to make the best use of what we already know. “There is much more the United States and the world and be doing to prevent cancer. Right now,” they wrote.

Perhaps one the biggest hurdles in putting prevention to work, however, has been our own rush to see results. “Humans are impatient, and that human trait itself is an obstacle to cancer prevention,” they noted. “Studies that focus on short-term exposures or short-term follow-up almost certainly will miss the true benefits of prevention.”

For example, despite reductions to the amount of asbestos workers could be exposed to starting in the 1970s in the UK, rules were slow to be fully implemented and extended to lower levels of exposure. So, asbestos-related cancers will probably keep rising there until 2020. Likewise, on an individual level, someone who quits smoking drops his or her risk of lung cancer by 13 percent in the first five years after stopping. Not bad, but by 10 years out, the risk drops by 33 percent.

So to really prevent more cancers over the long haul, researchers and policy makers should take the long view—interventions and study participants should be followed not for two or five years, the researchers noted, but for 20 and beyond. And these studies should start earlier. Many cancers take decades to develop, and even lifestyle choices made in our youth, such as alcohol use and lack of physical activity, can impact cancer risk down the road. So to realize the biggest results, the authors noted, “studies and interventions should be targeted at the early stages of the human life span, but this rarely happens.”

Colditz and his colleagues also argued that achieving dramatic cuts to cancer incidence requires immediate action—individually and collectively. “Each passing year leaves a substantially greater portion of the world population at risk for cancer, despite our current knowledge,” they wrote. “We have a moral responsibility to act now and reduce that burden.”

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