One Third of Cancer Deaths Could Be Prevented by Lifestyle

Kristin Jenkins

December 22, 2017

As we head into the festive season, many are looking forward to the tradition of "Eat, drink, and be merry." But as another research paper shows that more than a third of cancer deaths could be prevented by lifestyle, maybe a qualifier should be added:"celebration in moderation."

The latest statistics come from Australia, where researchers note that 44,004 cancer deaths occurred in 2013. But an estimated 38% of these deaths and 33% of cancer diagnoses could have been prevented with healthy lifestyle choices, says a research team led by Louise Wilson, MEpi, at the QIMR Berghofer Medical Research Institute and the University of Queensland, Brisbane.

These cancer diagnoses and deaths were seen in Australians of all ages and are directly attributable to 20 known modifiable risk factors within eight categories that are established causes of cancer, the study authors say.

The report is published in the February 2018 issue of the International Journal of Cancer.

Smoking was the leading cause of preventable cancer death in Australia in 2013 and accounted for 23% of all cancer deaths. The study authors estimate that about two thirds of the tobacco-attributable cancer deaths were due to lung cancer.

"We have shown that a large proportion of cancer cases in addition to deaths from cancer are, in theory, preventable," the authors write.

"We estimate that about 16,700 cancer deaths and 41,200 cancer cases could be prevented in Australia each year if people's exposures to 20 causal factors were aligned with levels recommended to minimise cancer risk…. Even modest reductions in population exposure to known causes of cancer would likely translate to sizable reductions in premature deaths from cancer," they write.

Three other categories of modifiable risk factors — poor diet, overweight/obesity, and infections — accounted for 5% of cancer deaths each. In a fifth category, alcohol-related cancer accounted for 2.4% of deaths. Physical inactivity factors were responsible for 0.8% of cancer deaths, overexposure to ultraviolet radiation for 3.2% of cancer deaths, and, in the eighth category, reproductive or hormonal factors were linked to 0.4% of cancer deaths.

The study authors first described these risk factors and categories in a 2010 report. At that time, they estimated that 1 in 3 of the 130,000 newly diagnosed cancers in Australia (33% of cancers in men and 31% of cancers in women) were attributable to these 20 modifiable causes.

For Australians younger than 75 years of age, avoiding exposure to known causes of cancer could have saved even more lives in 2013, the researchers say. That year, preventable cancer deaths accounted for 43% of overall cancer deaths in this age group, including 47% of cancer deaths in men and 38% of cancer deaths in Australian women.

To quantify cancer incidence and mortality from 2013 Australian Institute of Health and Welfare data, the researchers used exposure prevalence and relative risk. Then they calculated the proportion of cases and deaths that could be avoided through reduced exposure to known modifiable risk factors.

In the diet category, risk factors include low intake of fruit, nonstarchy vegetables, and dietary fiber and high intake of red and processed meat. In the infection category, seven cancer-causing agents, including human papillomavirus (associated with cancer of the vulva, vagina, penis, anus, oral cavity, and oropharynx) and Helicobacter pylori (noncardia stomach cancer), are included.

Lack of breastfeeding, use of menopausal hormone therapy, and use of combined oral contraceptive use (breast and cervical cancer) are listed as preventable risk factors in the reproductive category.

These findings are in keeping with other research on the role of modifiable lifestyle-related risk factors in cancer prevention. As previously reported by Medscape Medical News, results from a large cohort study in the United States led researchers to conclude that 20% to 40% of cancer cases and related mortality could be prevented by not smoking, maintaining a healthy weight, and exercising regularly.

In another report, results from a national online survey undertaken by the American Society of Clinical Oncology showed that, like their Australian counterparts, most US adults don't know alcohol and obesity are major risk factors for cancer.

When asked if the researchers were surprised by the high percentage of Australians diagnosed with cancers that have known, avoidable risk factors, Wilson said, "Not necessarily."

"We know that, on the whole, a large proportion of the Australian population is overweight or obese; doesn't eat sufficient fiber, fruit, or vegetables; and doesn't get enough exercise," she told Medscape Medical News.

The incidence of other preventable cancers could also be reduced through lifestyle choices, such as eating a balanced diet, being physically active and maintaining a healthy body weight, cutting back on alcohol, and using sun protection, she noted.

Clinicians can play a key role in raising awareness by talking to patients about how to lower their risk, Wilson pointed out. "Clinicians, in particular, are best positioned to have an impact at the individual patient level."

In 2013, the high proportion of smoking-related cancer deaths was observed despite Australia's aggressive smoking cessation public health strategies. Many Australians older than 40 years of age were smokers in their youth, explained Wilson. Most were men. The researchers factored in the cumulative effects of both past and current smoking, as well as exposure to secondhand smoke.

Today, the number of Australians who smoke has dropped dramatically, and the country has one of the lowest proportions of daily smokers in the world. "If this low prevalence continues, repeating this analysis 10 years from now should see a reduction in the tobacco-attributable cancer deaths," Wilson predicted.

Until then, the number of cancer deaths in Australians remains high. Nearly 48,000 out of a population of 24.5 million are expected to die of cancer in 2017, accounting for 30% of all deaths.

This study was funded by the National Health and Medical Research Council and by Cancer Council Australia. Ms Wilson and study coauthors have disclosed no relevant financial relationships.

Int J Cancer. 2018;142:691-701. Abstract

Follow Medscape Oncology on Twitter: @MedscapeOnc

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