Cancer is a leading killer, but healthy living can help to prevent it.
Cancer is the second leading cause of death in the U.S., with 1.6 million new cancer cases and 0.6 million cancer deaths expected to occur in 2016.
Recent research has suggested that random mutations during stem cell divisions could be a major factor leading to cancer development.
Some have interpreted these findings to mean that only a third of the variation in cancer risk in tissues is due to environmental or genetic factors, and most is due to "bad luck."
However, many studies have produced strong evidence that lifestyle factors play a role.
Dr. Mingyang Song and colleagues, from the Harvard T.H. Chan School of Public Health in Boston, MA, have been looking at how a "healthy lifestyle pattern" impacts cancer incidence and death.
They studied data for 89,571 women and 46,399 men.
50 percent of cancer deaths could be prevented with a healthy lifestyle
Four criteria were defined as representing a "healthy lifestyle pattern:"
- Never smoking or having quit smoking
- Drinking either no alcohol, or a maximum of one drink a day for women, and two or less for men
- A body mass index (BMI) above 18.5 but below 27.5
- Weekly aerobic exercise - either 150 minutes or more of moderately intense activity, or 75 minutes of vigorous exercise.
Individuals who met all four criteria were considered at low risk; those who did not were at high risk.
At low risk were 16,531 women and 11,731 men who had a healthy lifestyle pattern. The remaining 73,040 women and 34,608 men were considered to be at high risk.
The team then calculated the proportion of cases that would be avoided if all participants followed the healthy lifestyle pattern adhered to by the low-risk group.
Results suggest that around 20-40 percent of cancer cases and about 50 percent of cancer deaths could possibly be prevented if people modify their lifestyle to fit the healthy pattern of the low-risk group.
The team also looked at the risk for some specific cancers. For lung cancer, 82 percent of cases could be prevented in women and 78 percent in men. For colorectal cancer, a healthy lifestyle could reduce the risk by 29 percent for women and 20 percent for men.
For women, the risk of developing breast cancer was 4 percent lower with a healthy lifestyle, and the risk of death from breast cancer was 12 percent lower.
For men, a healthy lifestyle could decrease the risk of fatal prostate cancer by 21 percent.
Limitations include the fact that all the participants included in the estimates were white. This means that the results may not apply to other ethnic groups. However, the same factors have been linked to a higher chance of cancer in a range of ethnic groups.
Prevention must become a priority
The authors say the findings emphasize the impact of lifestyle factors on cancer risk. They call for prevention to become a priority in the field of cancer control.
In a linked editorial, Dr. Graham A. Colditz and colleagues, from the Washington University School of Medicine in St. Louis, state that "most cancer is preventable." They note that up to 80-90 percent of smoking-related cancers are avoidable.
But they add that can take a long time to translate what we know into what we do.
They call on people and policymakers to grasp the idea that developing cancer is not necessarily a matter of chance, and to be more active in engaging in and encouraging healthy habits.
The authors say:
"As a society, we need to avoid procrastination induced by thoughts that chance drives all cancer risk or that new medical discoveries are needed to make major gains against cancer, and instead we must embrace the opportunity to reduce our collective cancer toll by implementing effective prevention strategies and changing the way we live."
In the future, they say, prevention efforts will provide the best return on the investment into cancer research that has already been carried out.