2018's Sudden Drop in Cancer Incidence

Cancer rates have been in decline for decades, often attributed to changes in habits, new approaches to cancer treatments, and early detection. But in 2018, that decline accelerated substantially.

Not just rates of cancer diagnosis, but the rate of deaths due to cancer dropped. The total number of deaths from cancer, which regularly increases year over year with the increasing population, leveled off.

Both declines are outside the 95 percent confidence intervals, with the 2018 drop in cases being the largest in the dataset, which goes back to 1999.

The decline in cases occurred across almost every type of cancer, with only five types of cancer seeing an increase in 2018. The largest decline was in mesothelioma (-9.4 percent) with ovarian cancer second (-5.7 percent). Lung cancer saw a moderate decline (-3.1 percent), but it is by far the largest type of cancer in terms of total numbers.

American Cancer Society Estimates

The American Cancer Society produces annual estimates based on data from three years prior that usually tracks with CDC data. But in 2018 those estimates diverged. Their estimates predicted cancer cases would continue to grow year over year, increasing by around 20,000-40,000 each year from 2017 to 2020. Instead they dropped by 30,000 in 2017-2018, going from 1,738,258 to 1,708,921.

The implication being that the Cancer Society didn’t see the drop in cases or deaths coming. It takes three years for CDC to update its mortality data so the most recent year on record is currently 2018. Cancer Society estimates are based on that three-year prior CDC data.

Neither the CDC nor the Cancer Society note the cause of a larger drop in incidence and death rates. Although both note that the pandemic will have a unique effect as disruption of health services interrupted treatments and screenings.

President Biden recently announced the relaunch of the “cancer moonshot” initiative that aims to cut the mortality rate in half.