About 42% of cancer cases and 45% of cancer deaths in the United States are linked to modifiable risk factors – and thus could be preventable – according to a new study from American Cancer Society researchers. These figures, based on data from 2014, translate to:
The researchers came up with the estimates by calculating how much certain lifestyle factors contributed to 26 different cancer types among adults ages 30 and older. These risk factors included:
For the analysis, the researchers first looked at the prevalence of these known risk factors and their relative risk – that’s the extent to which the risk factors can increase cancer risk. They used that information to estimate the proportion of cancers associated with those risk factors. Then they applied those proportions to actual cancer diagnosis and death data to estimate the total numbers of associated cancer cases and deaths. The results were published Nov. 21 online in CA: A Cancer Journal for Clinicians.
The authors used data from the Centers for Disease Control and Prevention and the National Cancer Institute. The authors say their study improves upon past analyses because they included more risk factors and cancer types and they used nationally representative and up-to-date data.
The authors write that although the cancer mortality rate has declined by 25% since 1991, the overall cancer burden is still high. The American Cancer Society estimates that more than 1.6 million new cancer cases and 600,000 cancer deaths will occur in 2017. The researchers say their findings can help leaders set priorities for cancer prevention and control.
The authors analyzed each risk factor’s contribution to overall cancer cases and deaths in 2014. Cigarette smoking topped the list.
When the researchers grouped together the related issues of excess body weight, alcohol intake, poor diet, and physical inactivity, they found this set of risks was responsible for a total of about 18% of cancer cases and 16% of deaths.
The researchers also looked at the 26 cancer types individually to find out which ones had the biggest links to the lifestyle risk factors.
They found the proportion of cases linked to modifiable risk factors ranged from a high of 100% for cervical cancer and Kaposi sarcoma to a low of 4.3% for ovarian cancer. More than 75% of the melanoma, anal, lung, larynx, and oral cavity cancer cases and deaths could be attributed to modifiable risk facts. And the proportion of cancer cases connected to modifiable risk factors was greater than 50% for 15 of the 26 cancer types analyzed.
When looking at the total numbers of cancer deaths by type that were linked to modifiable risks:
The study detailed the extent to which each risk factor contributed to each cancer type.
The authors highlighted important differences by gender.
The authors stated that doing more to increase the awareness and availability of prevention strategies that we already know work is vital to reducing the number of preventable cancers. They call out strategies such as taxing cigarettes to reduce smoking and increasing vaccination rates to protect against cancer-causing HPV infections.
Otis W. Brawley, MD, American Cancer Society chief medical officer and study co-author says this new study provides critical information that will help guide cancer and public health leaders in the years ahead.
Importantly, the researchers noted that modifiable risk factors might be responsible for even more cancer cases and deaths than they were able to estimate in their paper. The study's lead author, American Cancer Society researcher Farhad Islami, MD, PhD , explained: “We lacked nationally representative data for several other potentially modifiable risk factors...and, we did not consider many likely, but as-yet unestablished, associations between certain risk factors and other cancer types.”
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Proportion and Number of Cancer Cases and Deaths Attributable to Potentially Modifiable Risk Factors in the United States; Farhad Islami et al. CA Can J Clin DOI 10.3322/caac.21440