Significant Amount of Cancer Cases Attributable to Potentially Modifiable Risk Factors

Approximately 42% of all incident cancer cases in the US in 2014 were attributable to potentially modifiable exposures, such as alcohol intake and excess body weight, according to a new study.

“Many cancers are causally related to potentially modifiable risk factors, and contemporary estimates of this proportion in a population are a valuable tool for setting priorities for cancer prevention and control,” wrote the authors of the study.

The study, published in CA: A Cancer Journal for Clinicians, estimated the population-attributable fraction (PAF) of cases and deaths overall and for 26 cancer types in adults age 30 years or older in 2014 that were attributable to potentially modifiable risk factors.

Risk factors with sufficient evidence for causing cancer were identified from reports published by the International Agency for Research on Cancer (IARC) and the World Cancer Research Fund/American Institute for Cancer Research (CRF/AICR). Among the 17 risk factors were:

• Smoking (first- and second-hand)
• Ultraviolet (UV) radiation
• Alcohol intake
• Excess body weight
• Low fiber intake
• Consumption of processed and red meat
• Low intake of fruits and vegetables
• Human papillomavirus (HPV) infection
• Lack of physical activity

Data on the number of cancer cases and cancer deaths were obtained from the CDC’s National Program of Cancer Registries and the National Cancer Institute's Surveillance, Epidemiology, and End Results program. Exposure data were based on sex- and age-specific prevalence estimates from national representative surveys.

The authors examined 1,570,975 incident cancer cases, 42% of which were attributable to the potentially modifiable risk factors evaluated. Of the 587,521 cancer cases that resulted in death, 45.1% were attributable to the risk factors. Cigarette smoking had the highest PAF (19% of all cases), accounting for nearly 56% of all potentially preventable cancers in men and 35% in women. Lung cancer had the highest amount of smoking-attributable cases (81.7%).

Excess body weight had the second highest PAF (7.8%) and was associated with 4.8% of all cancers in men, and 10.9% of all cancers in women. The disease accounted for more than half of all cancers of the corpus uteri (60.3%) and 1 in 3 cases of gallbladder (35.5%), liver (33.9%), and kidney/renal pelvis (33.2%) cancer.

Alcohol intake was the third largest contributor for women (6.4%), with the majority of the burden for breast cancer, and the fourth largest for men (4.8%). It was attributable to 1 in 4 cases of esophageal, oral cavity, and pharyngeal cancers in women, and nearly half of oral cavity and pharyngeal cancers in men.

The amount of cancers attributed to poor diet ranged from 0.4% for low dietary calcium intake to 1.9% for low fruit and vegetable intake. For colorectal cancer specifically, the PAFs ranged from 4.9% for low dietary calcium intake to 10.3% for low dietary fiber intake. Red and processed meat consumption was associated with 5.4% and 8.2% of colorectal cancers, respectively.

Other PAFs included: 4.7% for UV radiation, 2.9% for physical inactivity, and 1.8% for HPV infection.

“Our findings emphasize the continued need for widespread implementation of known preventive measures in the country to reduce the morbidity and premature mortality from cancers associated with potentially modifiable risk factors,” concluded the authors.