In US, 4 out of 10 Cancers Could Be Prevented

Pam Harrison

November 21, 2017

More than 4 out of 10 cancer cases among adults in the United States and almost half of all cancer-related deaths are associated with potentially modifiable risk factors, an American Cancer Society study indicates.

"An estimated 42% of all cancer cases and nearly one-half of all cancer deaths in the United States in 2014 were attributable to evaluated risk factors, many of which could have been mitigated by effective preventive strategies," say Farhad Islami, MD, PhD, strategic director, cancer surveillance research, American Cancer Society, Atlanta, Georgia, and colleagues.

"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," they add.

The study was published online November 21 in CA: A Cancer Journal for Clinicians.

New Invasive Cancers

Information on cases of new invasive cancers in 2014 was obtained from the Centers for Disease Control and Prevention's (CDC's) National Program of Cancer Registries and the National Cancer Institute's Surveillance, Epidemiology, and End Results program.

Information on deaths from cancer came from the CDC's National Center for Health Statistics.

"Cigarette smoking was associated with far more cancer cases and deaths than any other single risk factor, accounting for nearly 20% of all cancer cases and 30% of all cancer deaths," the study authors observe.

The most common cancer caused by smoking was lung cancer, but smoking also contributed to a large number of cancers of the larynx, the esophagus, and the oral and nasal cavities.

Excess body weight was the second most common modifiable risk factor associated with cancer, causing 7.8% of all cancer cases and 6.5% of all cancer-related deaths.

Importantly, excess body weight was responsible for a disproportionate number of cancers of the uterus, at approximately 69%, as well as more than a third of cancers of the gallbladder and about a third of cancers of the kidney and renal pelvis.

"Alcohol intake was the third largest contributor to all cancer cases among women...and the fourth largest contributor among men," at 6.4% and 4.8% of all cancers, respectively, the researchers note.

Overall, alcohol was associated with 5.6% of cancer cases and 4% of cancer deaths, they add.

The researchers also found that almost 50% of oral cavity and pharyngeal cancers in men were associated with alcohol consumption. Human papillomavirus (HPV) was also a cause of oral and pharyngeal cancers, especially among middle-aged men.

Dietary factors contributed variably to potentially preventable cancers in men and women, the researcher add. Such factors include suboptimal consumption of dietary calcium; low consumption of fruit, vegetable, and dietary fiber; and the consumption of too much red meat and processed meat.

The population-attributable fraction (PAF) of several of these dietary risk factors for colorectal cancer was quite high, depending on the risk factor assessed.

Table. Poor Diet and Cancer Risk

  Proportion of All Cancer Cases Overall PAF for Colorectal Cancer
Low dietary calcium consumption 0.4% 4.9%
Low fruit and vegetable consumption 1.9% NA
Low dietary fiber consumption NA 10.3%
Red meat consumption NA 5.4%
Processed meat consumption NA 8.2%


Physical Inactivity

Being physically inactive was associated with slightly less than 3% of all cancer cases overall. Physical inactivity was responsible for slightly higher rates of breast cancer in women.

Indeed, "the combination of excess body weight, alcohol intake, poor diet, and physical inactivity accounted for the highest proportion of all cancer cases in women and was second only to tobacco smoking in men," the investigators observe. "These findings underscore the importance of adherence to comprehensive guidelines on weight control, alcohol, diet and physical activity," they note.

The researchers found that virtually all cases of melanoma were due to exposure to ultraviolet (UV) light. The analysis did not include cases of nonmelanoma skin cancers.

Exposure to UV radiation was the second biggest contributor to total cancer cases in men, at 5.8%. It was a smaller contributor to cancer cases in women.

The researchers estimate that 3.3% of all cancer cases were caused by infections. Hepatitis B and C and HPV were prominent among the infectious agents.

"The proportion of all cancer deaths attributable to evaluated risk factors in 2014 was men, women, and 45.1% in both sexes combined," the investigators write.

"[W]e likely underestimated the actual proportions of cancers attributable to some individual risk factors and all potentially modifiable factors combined," they add.

The authors have no disclosed no relevant financial relationships.

CA Cancer J Clin. Published online November 21, 2017. Full text

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