Nearly Half of Cancer Cases Are Linked to Modifiable Risk Factors, Study Finds

A new study has found that 40% of cancer cases, and nearly 50% of all cancer deaths, are linked to “modifiable risk factors” such as cigarette smoking, excess body weight and alcohol consumption.

The research is published in CA: A Cancer Journal for Clinicians.

Informing cancer prevention efforts

Many so-called “modifiable risk factors” can increase our risk of developing cancer. Understanding what these factors are and to what extent they contribute to different cancer types is important to help guide cancer prevention methods.

A previous study estimated the proportion of cancers in 2014 linked to these risk factors, but more recent data is needed to guide prevention methods and to control the number of cancer cases.

To this end, researchers from the American Cancer Society have analyzed more up-to-date cancer risk and occurrence data from 2019, estimating the proportion of cancer cases and deaths in US adults over 30 years of age.

Cigarette smoking is a major risk factor

The researchers estimated the number of cancer cases and deaths linked to potentially modifiable risk factors using nationally representative data on cancer incidence, mortality and risk factor prevalence.

These modifiable risk factors included: smoking history, excess body weight, alcohol consumption, red and processed meat consumption, dietary fiber and physical inactivity. They also added infection history, as some infections – such as the Epstein-Barr virus, human papillomavirus (HPV) and human immunodeficiency virus (HIV) – are known to increase the risk of cancer.

Cigarette smoking had the largest proportion of cancer cases, or population attributable fraction (PAF). Smoking was linked to 19.3% of all cases, as well as 56% of potentially preventable cancers in men and 39.9% in women.

Excess body weight had the second largest PAF at 7.6%, followed by alcohol consumption (5.4%), UV radiation exposure (4.6%) and physical inactivity (3.1%).

Next, the researchers examined the proportion of specific cancer types caused by potentially modifiable risk factors. Cervical cancer and Kaposi sarcoma had the highest PAF at 100%, with ovarian cancer at the bottom of the list at 4.9%.

For many cancer types, over 80% of cases were attributable to these modifiable risk factors. These included 92.2% of melanomas, 94.2% of cancers of the anus, 89.9% of larynx cancers and 83.7% of oral cavity cancers.

Lung cancer had the largest number of cases attributable to evaluated risk factors in both men (104,410 cases) and women (97,250). For men, this was followed by melanoma (50,570), colorectal cancer (44,310) and urinary bladder cancer (32,000), and for women breast (83,840), corpus uteri (35,790) and colorectal (34,130) cancer.

“These findings show there is a continued need to increase equitable access to preventive health care and awareness about preventive measures,” explained the study’s senior author Dr. Ahmedin Jemal, senior vice president of surveillance and health equity science at the American Cancer Society. “Effective vaccines are available for hepatitis B virus, that causes liver cancer and HPV, which can cause several cancer types, including cervical, other anogenital, and oropharyngeal cancers. Vaccination at the recommended time can substantially reduce the risk of chronic infection, and consequently, cancers associated with these viruses.”

What can be done to tackle these risk factors?

“Despite considerable declines in smoking prevalence during the past few decades, the number of lung cancer deaths attributable to cigarette smoking in the United States is alarming,” explained the study’s lead author Dr. Farhad Islami, senior scientific director in cancer disparity research at the American Cancer Society.

“This finding underscores the importance of implementing comprehensive tobacco control policies in each state to promote smoking cessation, as well as heightened efforts to increase screening for early detection of lung cancer, when treatment could be more effective,” he added.

“Interventions to help maintain healthy body weight and diet can also substantially reduce the number of cancer cases and deaths in the country, especially given the increasing incidence of several cancer types associated with excess body weight, particularly in younger individuals.”

Reference: Islami F, Marlow EC, Thomson B, et al. Proportion and number of cancer cases and deaths attributable to potentially modifiable risk factors in the United States, 2019. CA Cancer J Clin. 2024. doi: 10.3322/caac.21858

This article is a rework of a press release issued by the American Cancer Society. Material has been edited for length and content.