Where do cancer risk statistics come from?

Most information about cancer risk and risk factors comes from studies that focus on large, well-defined groups of people. Cancer researchers have identified many of the major environmental factors that contribute to cancer, including smoking for lung cancer and sunlight for skin cancer. Uncovering more subtle cancer risks has proved more difficult.

Many studies of cancer risk factors rely on observational approaches. In these studies, researchers keep track of a group of people for several years without trying to change their lives or provide special treatment. This can help scientists find out who develops a disease, what those people have in common, and how they differ from those who didn't get sick.

How do cancer risk statistics relate to you?

Risk statistics can be frustrating because they can't tell you your risk of cancer. Studies may have found that men have a nearly 45 percent chance of developing cancer in their lifetimes, but that doesn't mean your risk is 45 percent. Your individual risk is based on many different factors, such as age and habits (including eating habits), family history of cancer, and the environment in which you live.

Even then, the combination of risk factors might not apply to you. Cancer is individualistic. You can have two people with the same age, sex, race, socio-economic status and comparative lifestyles and still have different experiences. Risk statistics are helpful in general statements such as "exercising regularly coincides with a reduced risk of chronic diseases, such as cancer." But exercising regularly won't guarantee that you won't get cancer.

Talk with your doctor about your risk of cancer. He or she can review what elements in your life may increase your risk. You can then discuss what to do to help lower this risk.

Keep cancer risk statistics in perspective

You might hear a news report about a study that seems to indicate you may be at increased risk of a particular type of cancer. Don't jump to conclusions based on this one report. Take a step back and think about what the risk really means.

Observational studies aren't foolproof. Researchers agree that one study by itself isn't authoritative. This is why you sometimes see studies with seemingly contradictory results.

Scientists weigh the evidence of many research studies over time to better determine whether a finding is true. News reports, though, focus on each new study in isolation, rather than as a part of an evolving picture. This can sometimes cause unnecessary alarm or confusion.

When you read or see a report about cancer risk statistics, pay attention to these details:

  • Who's being observed? A news report may say a certain activity increases the risk of cancer for a group of people. But who was being observed in the study? Pay attention to the ages of the people and their characteristics. For instance, some people are genetically predisposed to certain types of cancer.
  • How many people were studied? In general, studies involving thousands of people are more accurate than are those that examine a small group of people.
  • Have similar studies been done? The findings of one study are more reliable if they're similar to findings by other studies. Sometimes, the study wasn't carried out for enough years to make it statistically significant.

News reports that focus on alarming statistics, such as a 300 percent increase in risk, but don't give you context aren't helpful. If you're concerned about the risk, gather more information and talk to your doctor.

Mar. 01, 2014 See more In-depth