DEAR DOCTOR K:
A while back, you commented on a study that said getting cancer was mainly caused by bad luck. You said you thought the study was wrong. Then recently, I heard that another study agreed with you. Can you explain?
In April 2015, I responded to a question about a study from a famous cancer researcher. The media had interpreted the study to say that getting cancer was just a matter of “bad luck.” In other words, there was not much people could do to protect themselves against getting cancer.
As I read the original study, I thought its main point was to explain why cancer affects certain organs more than other organs. The authors did say that certain types of cancer clearly were caused by factors a person could control. For example, not smoking greatly reduces the risk of lung (and several other) cancers. However, the way the study was presented led the media to conclude otherwise.
The paper created a firestorm among cancer researchers. That’s because a lot of time and money are spent on cancer prevention programs. If getting cancer is just a matter of bad luck and can’t be prevented, then why bother trying to prevent it?
As you say, a new paper on this topic has just been published. It argues strongly that many cancers are caused by factors in the environment that can be controlled. The study concludes that only a small fraction of cancers are caused by factors such as defective genes (“bad luck”).
Sometimes genes that we inherit from our parents cause cancer. An example is the BRCA1 gene that causes some cases of breast cancer and ovarian cancer. Some people have the bad luck to inherit this gene. However, that doesn’t mean there is nothing a person can do about it. It is possible to test a person to see if they have inherited this gene. If so, the risk of cancer caused by the gene can be greatly reduced by careful monitoring and, if necessary, surgery.
The new paper concludes that 70 to 90 percent of cancers are caused by factors in the environment such as tobacco smoke, alcohol and sun exposure. This includes such common cancers as lung, colon, melanoma, stomach and prostate cancers.
It also includes somewhat less common cancers. For example, the paper cites studies finding that 75 percent of cases of esophageal cancer are caused by tobacco and excessive intake of alcoholic beverages. It estimates that the human papilloma virus causes 90 percent of cases of cervical and anal cancer. It concludes that infection of the liver by hepatitis B or hepatitis C viruses causes 80 percent of liver cancer.
By avoiding risk factors (like smoking and excessive sun exposure), by being tested for cancer-causing infections (like human papilloma virus) and by getting other cancer-screening tests, you can protect yourself.
As I said in my column last April, we can control our fate, though not completely. That’s true of minimizing our risk of cancer, as well. Cancer is not just a matter of bad luck.