Approximately 42 percent of cancer cases and 45 percent of cancer deaths in the United States are linked to lifestyle related risk factors including excess weight, poor diet and physical inactivity according to a study released last week. AICR estimates that nearly half of the most common US cancers could be prevented through these and other modifiable risk factors.
The study, published November 21 in the journal Cancer involved adults aged 30 and older and included 26 specific cancer types. The researchers at American Cancer Society used reports published by the World Cancer Research Fund/American Institute of Cancer Research (WCRF/AICR) to select potentially modifiable risk factors with sufficiently strong (either convincing or probable) evidence for causing cancer and for which risk factor exposure and cancer outcome data were available.
The potentially modifiable risks included cigarette-smoking, excess body weight, alcohol intake, consumption of red and processed meat, low consumption of fruits and vegetables and dietary calcium, physical inactivity, exposure to UV radiation, and specific infections. In a nutshell, these are the factors that are not inherited, and exposure to them is controllable.
Using government data on morbidity and mortality, the researchers concluded that 659,640 cancer cases and 265,150 cancer deaths yearly are linked to modifiable risk factors – and thus could be prevented.
Dr. Nigel Brockton, Director of Research at AICR says, “The study provides an excellent overview of the modifiable factors that contribute to the burden of cancer in the USA. Also, the number of cancer cases attributable to each risk factor can be viewed as a ranking of priorities for raising awareness and modifying those risk factors. Clearly, continuing to raise awareness around cigarette smoking remains a top priority but excess body weight, alcohol consumption, physical inactivity and low fruit and vegetable consumption are all top-ranking risk factors.”
The authors write that although 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 study is helpful in identifying the most urgent priorities so that cancer prevention efforts can be targeted most effectively,” says Brockton.
Risk Factor Rankings
- Cigarette smoking accounted for 19% of all cancer cases and nearly 29% of cancer deaths
- Excess body weight was responsible for 7.8% of cancer cases and 6.5% of deaths
- Alcohol was linked to 5.6% of cancer cases and 4% of deaths
- UV radiation was attributable to almost 5% of cases, but a lower 1.5% of deaths
- Physical inactivity played into 2.9% of cases and 2.2% of deaths
When researchers grouped together problems 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.
Total numbers of cancer deaths linked to modifiable risks:
lung cancer was at the top for both men and women, with more than 132,960 deaths;
colorectal cancer followed, again for both men and women, with 28,900 deaths;
liver cancer in men (9,860 deaths) and breast cancer in women (11,370 deaths) took the third spot.
Putting it Together –
The authors stated that doing more to increase the awareness and availability of prevention strategies, which we already know work, is vital to reducing the number of preventable cancers. They call for reinforcing strategies such as taxing cigarettes to reduce smoking and increasing vaccination rates to protect against cancer-causing infections.
Importantly, the study noted that modifiable risk factors might be responsible for even more cancer cases and deaths than they were able to project in their paper. The study’s lead author, American Cancer Society researcher Farhad Islami, 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.”
Dr. Brockton says, “This report also highlights the cancer types for which there is limited evidence that potentially modifiable factors contribute to the disease; the future prevention of these cancers will depend upon identifying those factors or improving detection of pre-malignant disease.”
Mapping Risks Factors to Cancer Types
The study detailed the extent to which each risk factor contributed to each cancer type
Cigarette smoking was linked to –
81.7% of lung cancers
73.8% of laryngeal cancers
50% of esophageal cancers
46.9% of bladder cancers
Excess body weight was linked to
60.3% of uterine cancers
about one-third of liver cancers (33.9%)
11.3% of breast cancers in women
5.2% of colorectal cancers
Drinking alcohol was linked to
almost one-half of oral cavity and pharyngeal cancers in men (46.3%) and one-fourth (27.4%) in women
24.8% of liver cancers in men and 11.9% in women
17.1% of colorectal cancers in men and 8.1% in women
6.4% of breast cancers in women
Eating red and processed meat was linked to
5.4% and 8.2% of colorectal cancers, respectively
Diet low in fruits and vegetables was linked to
17.6% of oral cavity/pharyngeal cancers
17.4% of laryngeal cancers
8.9% of lung cancers
Low dietary calcium was linked to
4.9% of colorectal cases
Low dietary fiber was linked to
10.3% of colorectal cancer cases
Physical inactivity was linked to
26.7% of uterine cancers
16.3% of colorectal cancers
3.9% of female breast cancers
HPV infection was linked to
All cervical cancers
88.2% of anal cancers
64.6% of vaginal cancers
UV radiation from the sun or indoor tanning was linked to
96.0% of melanomas of the skin in men
93.7% of melanomas of the skin in women