More than a third of the world’s cancer deaths in 2001 stemmed from nine potentially modifiable risk factors, new research shows.

Those nine risk factors are:

—Smoking

—Being overweight or obese

—Physical inactivity

—Low intake of fruits and vegetables

—Alcohol use

—“Unsafe” sex

—Indoor smoke from household use of solid fuels

—Contaminated injections in health care settings

—Air pollution

The list comes from researchers including Goodarz Danaei, MD, of Harvard School of Public Health and Harvard’s Initiative for Global Health.

Their report appears in The Lancet.

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The study focuses on the 7 million people worldwide who died of cancer in 2001.

About 2.43 million of those deaths might have been preventable, by the researchers’ estimate.

They did some elaborate calculations to arrive at that number. They had to weigh cancer research, as well as data from the World Health Organization (WHO).

Some WHO countries have more medical resources (and better health records) than others.

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Worldwide Trends

The researchers took a closer look at those 2.43 million cancer deaths. Their findings include:

—More than a third of those deaths (37 percent) were from lung cancer.

—Most of the deaths (1.76 million) happened in low- and middle-income countries.

—Men accounted for 1.6 million of those deaths, compared with 0.83 million women.

Smoking, alcohol use, and weight problems (being overweight or obese) were “the most important causes of cancer” in high-income countries, write the researchers.

Sexual transmission of the human papillomavirus (HPV) — which can cause cervical cancer — was a big risk factor for women in low- and middle-income countries, the study also shows.

Other scientists are working on vaccines that target the forms of HPV that cause most cervical cancers. Meanwhile, using protection to avoid infection might help, write Danaei and colleagues.

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Lowering Your Risk

It’s often hard to know exactly why someone gets cancer. You can’t change your genes or instantly get rid of the world’s air pollution.

But many other steps could be doable.

Does the researchers’ list ring any bells for you? You may want to talk to your doctor about ways you could lower your cancer risk and about cancer screenings you should get.

By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Danaei, G. The Lancet, Nov. 19, 2005; vol 366: pp 1784-1793. News release, The Lancet. American Cancer Society: “What Is Melanoma Skin Cancer?” American Cancer Society: “What Is Lymphoma?”