Cancer death rates in the United States fell 2.2 per cent from 2016 to 2017 – the largest single-year drop ever recorded – fueled in large part by progress against lung cancer, the leading cause of cancer death, the American Cancer Society (ACS) reported on Wednesday.
Overall, cancer death rates in the United States fell 29 per cent from 1991 to 2017, driven by steady declines in deaths from lung, colorectal, breast and prostate cancers, according to the society’s annual report on cancer rates and trends published in CA: A Cancer Journal for Clinicians. The rates are based on the number of cancer deaths per 100,000 people in the United States.
“The report shows a continued striking decline in overall cancer mortality in the United States,” Dr Ned Sharpless, director of the National Cancer Institute (NCI), said in a phone interview with Reuters Health. “That trend shows no sign of abating.”
Study co-author Rebecca Siegel, scientific director of surveillance research at the ACS, attributes that to a doubling in improvement in lung cancer death rates, which fell 4 per cent in the study period. Lung cancer is the second-leading cause of death in the United States behind heart disease.
“If you take lung cancer out of the mix, the drop was only 1.4 per cent. It is truly the acceleration for lung cancer that is driving the record drop that we saw,” she said in a phone interview.
According to the report, progress in reducing lung cancer deaths has improved due to declines in smoking and advances in early detection and treatment.
Sharpless, who in November returned to the NCI after a stint as acting commissioner of the U.S. Food and Drug Administration, believes some of the gains in lung cancer are related to better therapies. But as the report only goes through 2017, the impact of many of the relatively new immunotherapies for lung cancer, such as Merck & Co’s Keytruda, Bristol-Myers Squibb’s Opdivo and others, as well as newer targeted treatments, have yet to be fully reflected in the mortality data.
“We think the lung cancer data are going to continue to improve for a few years,” he said.
Typically, mortality data in the United States is about three years behind the current year, due in large part to the need to confirm that deaths were actually linked with a cancer. Even so, Sharpless said, data on cancer deaths is the most important metric used by the NCI for planning purposes.
To make up for the lag, the ACS uses computer models of cancer and population trends to project what is currently happening in oncology.
In its latest report, ACS projects that in 2020 roughly 1.8 million new cancer cases and 606,520 cancer deaths will occur in the United States.
LINK TO OBESITY?
Progress has slowed for female breast and colorectal cancer, and has essentially levelled off for prostate cancer over the past decade, the report found.
The number of new cases of breast cancer has climbed by about 0.3 per cent per year since 2004, a rise linked in part to lower rates of fertility and increases in obesity.
In prostate cancer, the number of new cases fell sharply from 2007 to 2012, linked in part to decreased use of blood tests for prostate-specific antigen (PSA) to screen for these cancers in the wake of guideline changes. Some studies suggest the declines in new cases may be masking increases in more severe cancers, the report said.
The increase in more advanced prostate cancers may reflect success in easier-to-treat cancers, but it also may reflect decreased PSA testing, Sharpless said.
“It is concerning after seeing so much progress against prostate cancer to see it level off,” Sharpless said, adding that the NCI “has got to be open-minded about this and fund appropriate research, both clinical and basic science, to really tease this out.”
Sharpless also expressed concern that rapid declines in new cases of colorectal cancer are slowing in spite of the availability of effective screening tools, such as colonoscopy.
“There’s an increased incidence of mortality that we think is likely related to obesity,” Sharpless said.
The NCI has noticed in particular an increase in colon cancer deaths in people under age 40, who would be too young for routine screening. “That’s a concerning trend,” Sharpless said.
Obesity may also be playing a role in the slight rise in new cases of breast cancer.
“We have all this progress against smoking-related cancers but obesity is something that we’re just probably seeing the tip of the iceberg now in terms of the influence on cancer,” Siegel said.
She said excess body weight currently accounts for about 7 per cent of cancers. “I’m sure that proportion will continue to increase because it takes a decade or two before you see the influence on exposure reflected in cancer rates.”