Although a recent article in the journal Science and a subsequent press release about the article led to a spate of headlines implying that most cancer is due to “bad luck,” Dr. David Hunter, Vincent L. Gregory Professor in Cancer Prevention, writes that, in fact, most cancers are preventable.
Tobacco-associated cancers are largely preventable. There are also a variety of infectious causes of cancer—for instance, hepatitis B causes liver cancer, and HPV (human papilloma virus) causes cervical cancer—for which there are vaccines. Also, in the last ten years, we have established that obesity is associated with an increased risk for a wide variety of cancers. If you add all of these together, plus some others like occupational exposures to chemicals or exposure to radiation, it’s pretty easy as a thought experiment to prevent more than half of the cancer cases in the world.
Unfortunately, it is a tough road to actually achieve this level of prevention. The amount of cigarettes smoked in the U.S. has fallen by about half since the mid-1960s — and lung cancer rates have fallen — but globally there were more cigarettes smoked in the world in 2012 than in any other year in human history. So while as a nation we have made progress, that hasn’t translated globally. In fact, tobacco companies have expanded their markets to many new countries.
As for the hepatitis B vaccine, a lot of countries, particularly in Asia, have successfully introduced the vaccine early in life — which is when it needs to be given — but there are still many countries where it is not available. Similarly, we have had the HPV vaccine for four or five years, and there is some progress making it affordable in middle-income countries, but there is still a long way to go to vaccinate all girls in the world.