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 Overall, cancer death rates in the United States fell 29 percent
from 1991 to 2017, driven by steady drops 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 report shows a continued striking decline in overall cancer
mortality in the United States," Dr. Ned Sharpless, director of the
National Cancer Institute, said in a telephone interview with
Reuters Health. "That trend shows no sign of abating."
Study coauthor Rebecca Siegel, scientific director of surveillance
research at the ACS, attributes that to a doubling in improvement in
deaths from lung cancer, which fell 4% 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
percent. It is truly the acceleration for lung cancer that is
driving the record drop that we saw," she said in a telephone
interview.
Sharpless, who in November returned to the NCI after a stint as
acting commissioner of the Food and Drug Administration, believes
some of the gains in lung cancer are related to better therapies,
but given that the report only goes through 2017, many of the new
drugs for lung cancer, such as Merck's Keytruda, have yet to be
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 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
National Cancer Institute for planning purposes.
To make up for the lag, the ACS uses computer models of cancer and
population trends to project what's currently happening in cancer.
In its latest report, the Society projects that in 2020, roughly 1.8
million new cancer cases and 606,520 cancer deaths will occur in the
United States.
Nevertheless, progress has slowed for female breast and colorectal
cancer, and has essentially leveled off for prostate cancer over the
past decade.
The number of new cases of breast cancer has climbed by about 0.3
percent per year since 2004, a rise linked in part to lower rates of
fertility and increases in obesity.
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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. But some studies suggest the declines in
new cases may be masking increases in more severe cancers, the
report said.
Sharpless said the increase in more advanced prostate cancers may
reflect success in easier-to-treat cancers, but it also may reflect
decreased PSA testing.
"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.
Sharpless said the National Cancer Institute 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," he 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% 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."
SOURCE: https://bit.ly/35yPYvu CA: A Cancer Journal for Clinicians,
online January 8, 2020.
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