The U.S. cancer death rate has been dropping for 25 years, in part thanks to a decrease in smoking rates, but obesity-related cancer deaths are rising, according to a report from the American Cancer Society.
Cancer death rate falls after peaking in 1990
According to the report, which was published Tuesday in CA: A Cancer Journal for Clinicians, the U.S. cancer death rate peaked in the early 1990s. Since then, the rate has gradually fallen, dropping by 1.5% annually between 1991 and 2016, with a total decline of 27%. The cancer death rate declined by 34% among men and 24% among women over that time.
The main reason for the drop was a decline in deaths from lung cancer, which have decreased by almost 50% among men since 1991, the report found. According to Rebecca Siegel, the report's lead author, the decline was driven by the longer-term drop in smoking rates, which began in the 1960s.
The report also found that the gap in cancer death rates between blacks and whites has gotten smaller, mostly due to a decline in smoking rates among black teenagers that occurred between the late 1970s and early 1990s.
But some cancers are on the rise
While most cancer death rates are decreasing, obesity-related cancer death rates are rising, including death rates for cancers of the pancreas and uterus. According to the report, rates of endometrial cancer have increased, with about 60% of cases attributed to obesity.
Meanwhile, the rate of liver cancer has been rising since the 1970s, initially due to an increase in hepatitis C infections from drug misuse—but now because of obesity, with obesity accounting for a third of all liver cancer deaths, according to Siegel.
Colorectal cancer rates also have increased by about 2% each year since the mid-1990s. This increase could be attributed to obesity, but according to Siegel, many researchers think "something else is also going on." She said, "Everyone is scrambling to try to figure it out."
Cancer remains second-leading cause of death
Despite the decline in the overall cancer death, the report found that cancer still is the second-leading cause of death in the United States. According to the report, approximately 1.7 million cancer cases will be diagnosed in 2019.
The report also projected that slightly more than 600,000 U.S. residents will die from cancer this year.
Siegel said we've likely seen only "the tip of the iceberg regarding the influence of the obesity epidemic on cancer rates," saying that in much the same way as tobacco drove cancer rates in the past, obesity could drive them in the future.
Noel Weiss, a professor of epidemiology at the University of Washington who wasn't involved in the study, said, "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."
Weiss said the increase in colorectal cancer death rates is particularly "worrisome, especially if they continue as people get older." Further, he noted that obesity can cause structural changes in the liver, which could mean obese people are more likely to get liver cancer.
Len Lichtenfeld, interim CMO at the American Cancer Society, said the reduction in cancer death rates is "a notable achievement." He added, "We are on the right path," but "[w]e still have a long way to go" (Stobbe, AP/STAT News, 1/8; Marcus, Wall Street Journal, 1/8; Cortez, Bloomberg, 1/8; Knowles, Becker's Hospital Review, 1/8).
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