Experts warn obesity may soon be the driving force behind new cancer cases in the U.S.

U.S. cancer death rates for men, women and communities of color are falling, but obesity and unequal access to care could threaten hard-fought gains over the past two decades, a new report shows.

The annual American Cancer Society report, which measures cancer cases and deaths through 2018, paints a mixed picture of the nation’s effort to combat the second leading cause of death, said Farhad Islami, the report’s lead author and American Cancer Society’s scientific director of cancer disparity research.

Death rates for lung cancer and melanoma improved significantly, but recent progress on breast and colon cancer deaths slowed, and prostate cancer death rates flattened after years of decline, the report said.

Experts said long-standing efforts to curb cigarette smoking and tobacco use along with improved medical care have yielded significant improvements in lung cancer deaths.

“The decrease in smoking is a huge reason,” said Dr. Otis Brawley, a professor at Johns Hopkins University and former chief medical officer at American Cancer Society. “Keep in mind it is not just lung cancer, but smoking causes 18 different cancers.”

New medications to treat people with melanoma that spread to other parts of the body also improved survival rates, Islami said.

The new report, published in the The Journal of the National Cancer Institute, includes death rates by age, sex, race, and ethnicity from 2001 through 2018 based on death certificates reported to states and the Centers for Disease Control and Prevention’s National Center for Health Statistics.

Overall, cancer death rates fell at a faster rate from 2015 to 2018 compared with rates since 2001. Cancer death rates for men dropped 2.3% per year from 2015 to 2018, a faster than 1.8% decline each year from 2001 to 2015. Among women, cancer deaths dropped 2.1% per year from 2015 to 2018, compared with 1.4% per year from 2001 to 2015.

Cancer death rates also dropped among all racial and ethnic group from 2014 to 2018. But death rates overall remain higher among Blacks compared with whites and other racial and ethnic groups.

Despite slowing death rates in most types of cancer for men and women, not all trends were positive. Death rates increased from cancer in the brain, nervous system and pancreas among men and women. In men, oral and throat cancers are on the rise, and liver and uterine cancers in women.

However, experts warn that obesity could soon overtake smoking as the nation’s main driver of new cancer cases. And the figures show positive strides on common cancers such as breast and colon cancers have slowed. One possible factor is rising obesity, Islami said.

Brawley agrees an “energy imbalance” of eating too much and not exercising enough is putting more Americans at risk for cancer. Brawley cited previous research that predicted such rising obesity and lack of exercise would usurp tobacco this decade as the leading cause of cancer.

“Think about tobacco control pushing the rate down and energy imbalance pushing the rate up at the same time, “Brawley said. “And by the way, the cancers that are going up or the cancers that are not going down in death rate in this study are the ones most closely associated with energy imbalance.”

The data does not captures cancer cases and deaths since the beginning of the COVID-19 pandemic in 2020, but researchers fear a slowdown in screening during lockdowns could mean doctors and patients are missing early-stage cases.

“They may be diagnosed a year later,” Islami said. “Increasing the proportion of cancers at a more advanced stage will eventually translate to higher death rates, unfortunately.”

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