Cancer Deaths Decline 27% Over 25 Years

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Deaths from cancer dropped 27% over a quarter century, resulting in an estimated 2.6 million fewer cancer deaths during that period, according to a new report from researchers at the American Cancer Society.

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For most of the 20th century, overall cancer deaths rose, driven mainly by men dying from lung cancer, researchers noted. But since the peak in 1991, the death rate has steadily dropped 1.5% a year through 2016, primarily because of long-running efforts to reduce smoking as well as advances in detection and treatment of cancer at earlier stages, when prognosis for recovery is generally better.

The report represents “good news,” said Noel Weiss, professor of epidemiology at the University of Washington, who wasn’t involved with the report. “But there is still a long way to go. A reduction in cancer mortality does not mean it is zero or even close to zero. Cancer is still one of the leading causes of death among Americans.”

Despite the steady decline in overall death rates, the study’s authors also projected that in 2019, they expect 1.76 million new cancer cases and close to 607,000 cancer deaths in the U.S. The investigators based their conclusions on data compiled from various federal agencies and cancer registries but noted a lag time in the number of cases and deaths because it takes time to collect and analyze data. The study was published Tuesday in CA: A Cancer Journal for Clinicians.

Men die in the greatest numbers from lung, prostate and colorectal cancer, while women die primarily from lung, breast and colorectal cancer, according to the report, which also noted differences in cancer incidence and mortality between the sexes. Rates for some common cancers are increasing or stable in women, with the report finding an increase of 0.4% a year for breast cancer.

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Men had a 34% total decline in cancer mortality, compared with 24% for women, largely tracking lower trends in smoking. Lung-cancer incidence is declining twice as fast among men as women, which in part reflects that women historically took up smoking in large numbers later and were slower to quit.

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Electra D. Paskett, professor of cancer research and associate director of population science at the Ohio State University Comprehensive Cancer Center, said a number of hypotheses try to explain the connection between obesity and cancer and can vary depending on the cancer. She cited chronic inflammation and changes in estrogen as two possibilities.

Dr. Weiss of the University of Washington said obesity can cause structural changes in the liver, which might predispose individuals to liver cancer. More research needs to be done.

Amid the good news about the decline in the overall death rate, there are also some troubling signs that researchers say need to be addressed. Endometrial cancer has increased, and a large percentage of cases—around 60%—are attributed to obesity, according to Rebecca Siegel, strategic director of surveillance information services at the American Cancer Society and lead author of the new report.

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“We are probably only seeing the tip of the iceberg regarding the influence of the obesity epidemic on cancer rates,” said Ms. Siegel. Just as tobacco use drove cancer death rates in previous decades, Ms. Siegel said, obesity could influence future projections.

Among adults under the age of 55, the incidence of colorectal cancer has continued to increase almost 2% a year since the mid-1990s. Obesity may be a factor, but many researchers also think “something else is also going on,” said Ms. Siegel. “Everyone is scrambling to try to figure it out.”

Dr. Weiss, the cancer epidemiologist, said that the trends in colorectal cancer are “worrisome, especially if they continue as people get older.”

Incidence rates in cancers such as melanoma, liver, thyroid, uterine and pancreatic also continue to rise. In both men and women, liver cancer incidence is increasing more rapidly than any other cancer.

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According to the researchers, 71% of liver cancer cases can potentially be prevented through lifestyle changes, such as not smoking, greater physical activity, losing weight, and prevention of hepatitis B and C viruses. Approximately 24% of liver cancer cases result from chronic hepatitis C infection, the report found, with a threefold rise in reported infections from 2010 to 2016 because of the opioid epidemic, according to investigators.

The cancer report’s findings, Dr. Weiss said, suggest that “we can make a dent based on our own activities.”

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