"Behaviors such as poor diet choices, physical inactivity, excess alcohol consumption and unhealthy body weight could account for more than 20 percent of cancer cases, and could, therefore, be prevented with lifestyle modifications," Kohler said, adding that when tobacco exposure is considered, these modifiable issues are believed to be factors in two-thirds of U.S. cancer deaths.
As part of their cancer prevention efforts, leading cancer organizations, such as the American Cancer Society (ACS) and the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) have published recommendations on diet and physical activity.
How the Study Was Conducted and Results: Kohler and colleagues identified studies published within the past 10 years that analyzed adherence to ACS and the WCRF/AICR guidelines. The researchers' final review was based on 12 prospective cohort studies that examined the association between following either ACS or WCRF/AICR guidelines and cancer incidence and mortality. Study participants ranged from 25 to 79 years of age at baseline, and were mostly Caucasian. Standards for adherence varied in the 12 studies that comprised the review, leading to a wide range of results, but consistent patterns emerged, Kohler said.
The review showed that adherence to cancer prevention guidelines was associated with a 10 to 45 percent reduction in all cancer incidence and a 14 to 61 percent reduction in all cancer mortality.
The study also showed consistent reductions in the incidence of breast cancer (19 to 60 percent), endometrial cancer (23 to 60 percent), and colorectal cancer (27 to 52 percent) in both men and women.
The study showed no significant associations between adherence to guidelines and incidence of ovarian or prostate cancer, and associations with lung cancer varied depending on the study.
Kohler and colleagues reviewed studies that compared high adherence to the guidelines with lower adherence, and found that people who followed more of the cancer prevention recommendations derived stronger benefits. For example, Kohler said, in one study, women who followed at least five recommendations were 60 percent less likely to develop breast cancer than those who met no recommendations. For each additional recommendation met, the risk of breast cancer was reduced by 11 percent.
Author Comment: Kohler said the review indicates that physicians and public health officials should continue to emphasize cancer prevention recommendations to patients.
"If you adhere to these guidelines, you may reduce your risk of getting or dying from cancer, though the risk is not totally eliminated," she said, noting that family history and environmental factors also play a role in cancer incidence and mortality. "However, following these recommendations will lead to healthier lives overall and, in turn, reduce the risk for many major diseases."
Kohler said that the primary limitation of this review was the variation in studies. Therefore, she noted, the researchers were only able to summarize information, without establishing causality or specific reductions in cancer risk.
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